One key metric to determining power-module reliability is the storage temperature rating. When selecting a module, you need to be sure that the module manufacturer is independently verifying the stand-alone inductor component used in the power module. Inductor qualification tests are not standardized across companies and quantities, and ratings that appear on data sheets can be inconsistent.

High-temperature storage (HTS) testing involves exposing the device to a rating temperature for 1,000 hours, and then checking for consistent characteristics before and after the exposure. All TI power modules are rated to a storage temperature of 125°C or above, meaning that the devices are guaranteed to maintain performance (efficiency) even after exposure to high temperatures.

In addition to this test in the module qualification regimen, module inductor components are pre-screened to ensure that they will meet a storage temperature requirement of 150°C as stand-alone components. Although inductor data sheets often cite a storage temperature, TI’s power-module team has found that some inductors rated to a specified storage temperature on the data sheet may not be suitable for use in a particular switching-converter application. Without qualifying the inductors before prototype and production, frustration and redesigns may occur.

The reason for this unsuitability is that the thermal aging in the material occurs in some inductors after exposure to high temperatures. This well-known phenomenon may not have previously been much concern if you use your devices below 65°C, but it has a significant effect on devices made to operate at temperatures above 85°C. You can observe the change in material by thermally measuring the losses of the inductor under test currents, or by using the inductor in a switching converter and noting a drop in efficiency, especially in wide V_in or high-output-current devices. Although these two test methods may be complex, you can also determine thermal aging with two straightforward measurements, which TI uses to qualify and select inductor components.

Figure 1 shows two simple measurements that indicate HTS failure. Samples from four different inductor vendors are evaluated at 150°C with measurements every 168 hours, showing significant drops in both quality factor Q at the switching frequency, and shunt or core resistance measured without biasing the device. The inductors that fail this test demonstrate high losses post-exposure when used in a buck-converter application, in spite of a lack of any visually observable changes, or change to direct current resistance (DCR) or L₀. This impact would be more significant in a wide V_in device and/or a device with a high output current simply due to the increased leakage current flowing through the now-reduced shunt resistance of the inductor.

In the evaluation shown in Figure 1, feedback from TI enabled one vendor to sample a second device, using an improved magnetic material that did not demonstrate thermal aging (vendor A2 in Figure 1), which was then chosen for the TI module. The details of the exact revision made to the device are generally proprietary, but it is likely that the revised device had a different material formula than the first device.

Figure 1: Quality factor and core resistance as a function of test time for several inductor devices

Conclusion

TI has developed an independent inductor testing regimen for every inductor component selected for use in a power module. The HTS test is a critical aspect of TI reliability evaluation, enabling us to evaluate whether an inductor may exhibit significant core losses once exposed to high temperatures for an extended period.

This test is significant, since the deficiency may not be obvious when measuring only the inductance and DCR before and after exposure. Qualifying the inductor component by itself is critical to ensuring a reliable switching converter without revisions and reliability issues later in the design cycle.

Sensing technologies are changing safety and comfort functions inside vehicles, and it is becoming increasingly important to accurately determine whether and where a person is seated inside. According to San Jose State University, an average of 37 children die in a hot car each year, “more than half of [which occur] after a parent or guardian forgets them in a vehicle.”

Millimeter wave (mmWave) sensing technology can detect a person’s presence under even challenging environmental conditions like bright light and darkness. Unlike other sensing technologies, mmWave can pass through materials like plastic, drywall and clothing, allowing the sensors to be hidden behind a fascia and placed inside or under other materials inside the vehicle, making them contactless and nonintrusive. For example, an ultrasonic sensor cannot distinguish between a person and a static object, and cameras will fail to detect a baby in bright light or dark conditions.

The AWR1642 77GHz single-chip mmWave sensor with on-chip memory and a digital signal processor is a good fit for these applications because of its ability to sense very small movements, even breathing, that would indicate the presence of a person.

We used the AWR1642 evaluation module to demonstrate occupancy inside a static vehicle. The sensor is suspended from the sunroof for demonstration purposes, looking toward the back seat, as seen in Figure 1, though it would likely be placed inside the seat back, around the rear view mirror or even the roof in a real-world installation. The entire processing chain of detection, including algorithms for the removal of any static clutter that might exist, is implemented on the sensor. In Figure 1, baby Max is sleeping in the child seat, covered with a blanket. The sensor not only detects Max despite the blanket, but also accurately locates his position as the rear right position.

Figure 1: Child occupancy detection inside a car using a TI mmWave sensor. The mmWave sensor is suspended from the sunroof. The detection is shown in the graph visualization as a heat map. 

In Figure 2, two people are sitting side by side in the rear seat. Their occupancy, indicated by the two red boxes, is detected by the mmWave sensor. The scenario can be easily extended for occupancy detection in multiple rows of a vehicle because mmWave sensors can “see” and distinguish people at extended distances.

Figure 2: TI’s mmWave sensor detects two people sitting in a rear seat

In Figure 3, the sensor detects a person just outside the vehicle who could be a possible intruder. The same sensor that detects occupancy inside a vehicle can also detect people in the immediate vicinity. It’s also possible to implement advanced algorithms to distinguish between a person and a moving object, such as tree branches blowing in the wind.

Figure 3: TI’s mmWave sensor detects a possible intruder behind the vehicle

The Vehicle Occupant Detection Using AWR1642 reference design provides a system-level overview and the reference software processing chain for detection of two-person occupancy inside a vehicle. The TI Design Guide explains in detail the implemented algorithms and you can try the demo either in a lab environment or an actual vehicle to detect two-person occupancy. The demo is easily modifiable to extend to multiple people detection as well.

mmWave sensors are enabling solutions for not only advanced driver assistance systems (ADAS) but also body, chassis and in-cabin applications. Child occupancy detection is a feature in the European New Car Assessment Program (Euro NCAP) roadmap, with implementation expected by 2020. Automotive original equipment manufacturers (OEMs) and Tier-1s alike are looking for a sensing technology that can provide this feature in a contactless and nonintrusive way. Other critical factors include cost-effectiveness and solution form factor; mmWave sensors fit the equation, with its single-chip optimized bill of materials, small and compact size, and high resolution. I would be excited to see this sensing technology in my next car. Wouldn’t you?

(Please visit the site to view this video)

In Peter Balyta's unique role as president of Education Technology and vice president of academic engagement and corporate citizenship, he interacts with students and educators at all levels. In this ongoing series of "Inspire STEM" articles, Peter talks about how we all can help students get involved in science, technology, engineering and math.

Meet Quynh-Anh Dang: university biochemistry student, former Girl Scout and current Girl Scout ambassador, organizer of a STEM fair for under-served elementary students, identical twin. One of her role models is 19th-century STEM trailblazer Elizabeth Blackwell, who was the first woman to graduate with a medical degree.

“Elizabeth Blackwell was turned down by almost all of the medical schools, and she had to work hard to prove herself in what was then a males-only field,” Quynh-Anh said. “She had to have had the strongest motivation to do that. I wrote a book report about her in the fifth grade, and her story still sticks with me. She inspired me to find a project or cause that motivates me, to forget about all the stereotypes and my own fears, and to just go for it.”

Quynh-Anh is definitely going for it and has found her passion in the study of genetics. She is an identical twin – her sister, Quynh-Chi, is also a freshman biochemistry student at Southern Methodist University – and a high-school biology teacher opened her eyes to the genetic marvel of twins.

“When my teacher explained that my sister and I are the closest genetic match of any other two people in the world, and how the DNA of identical twins is formed through random mutations, it blew my mind,” Quynh-Anh said. “This had such personal relevance to me, and I decided to study bio-chemistry to learn more about myself.”

Closing the gap

There are lots of opportunities to improve gender diversity in STEM careers for women such as Quynh-Anh. Consider the statistics: Women – who comprise half of the overall workforce in the U.S. – account for only 25 percent of computer and mathematical roles and 14 percent of engineering roles.¹ While the statistics for social sciences (62 percent) and biological and life sciences (48 percent) are better,² the road to STEM equality continues to be long.

Attracting and retaining more women to be scientists, engineers, mathematicians and doctors will mean more innovation and creativity to solve some of the most difficult challenges of our time. One answer to narrowing the STEM gender gap lies somewhere between the right combination of introducing girls to math and science at an early age and in developing their self-confidence.

Building confidence

For the past year, I’ve gotten to know more about the great work that Girl Scouts of Northeast Texas (GSNETX) is doing to ensure that girls have every chance of becoming the next generation of scientists, engineers, innovators and leaders.

Jennifer Bartkowski, the chief executive officer of GSNETX, is leading the charge to change the way girls identify with and engage in math and science. Her work, and the work of the Girl Scouts organization overall, is critically important. In Texas alone, 67 percent of eighth-grade girls are not proficient in math.³ We can’t let girls back away from taking challenging math and science classes.

“We’re finding that girls are opting out of hard math and science classes, and that gap in confidence is what Girl Scouts is poised to correct,” Jennifer recently told hundreds of teachers during our company’s T3 International Conference in San Antonio. “I’d like all girls to reach their full potential, to have the skills to lead their own lives and to have every door open to them so that they can make the choices they want to make. Allowing girls to lead, to make choices, to solve real-world problems and explore solutions gives a girl-led approach that empowers them to take risks, to have confidence, to persist and to be resilient. These are all leadership components needed for STEM professionals.”

Jennifer often says that girls can’t be what they can’t see and that we need to show them women who are succeeding in STEM careers. I couldn’t agree more, and so does Quynh-Anh, who is a former member of Troop 434 and a Gold Award Girl Scout for the work she did in high school to organize a STEM fair for an under-served elementary school in her area. She continues to be active in Girl Scouts as an ambassador.

“Being a Girl Scout provided me exposure to all different fields of STEM and shaped my perception about what a career in STEM could be like,” she said. “We took field trips to places like the Frontiers of Flight museum, where we learned about aviation, and to the Dallas Zoo, where we talked to zookeepers and learned about zoology. Girl Scouts also fostered mentorship and collaboration between troop members, and I developed lifelong friendships. It also provided an environment where I wasn’t afraid to ask questions and where I was never told, ‘You can’t do that because you’re a girl.’ We must surround girls with support and to find answers to questions.”

Join the quest

Thanks to fearless women such as Quynh-Anh Dang and Jennifer Bartkowski – and Elizabeth Blackwell before them – progress has been made slowly but surely to bring gender diversity into the STEM workplace. But there is so much more to be done.

Here’s my challenge to you: Join the quest to prepare girls for a lifetime of leadership by getting involved. Whether volunteering in an ongoing capacity or for a one-time event, by working directly with girls or by making an impact at a council level, Girl Scouts has a volunteer opportunity for everyone. In the Dallas area, learn more at the Girl Scouts of Northeast Texas volunteer resource page or visit your local community’s Girl Scout website.

There are also many other volunteer opportunities available, including Girls Inc. and Big Brothers Big Sisters of America. Your local United Way is also a terrific resource.

If girls don’t possess a strong sense of self, the ability to think critically and problem-solve, to understand how to manage conflict, or to advocate for themselves, then their likelihood of entering and remaining in a STEM career declines greatly. Let’s work together to help girls think like scientists, mathematicians, doctors or engineers and make the STEM gender gap a challenge of the past.

Are you passionate about STEM? Share your thoughts in the comments section.

¹Bureau of Labor Statistics, March 2017 report

²National Girls Collaborative Project, State of Girls and Women in STEM

³The State of Girls: Emerging Truths and Troubling Trends, 2017, Girl Scout Research Institute Report

Introduction

In a previous blog titled “How to design a simple constant current/constant voltage buck converter,” I discussed how to design a constant current/constant voltage converter (CC/CV).  With the addition of a simple modification, the functionality can be modified to regulate the output power and operate within a constant power (CP) limit as the output voltage varies in the CC mode of operation.  This blog discusses the simple modification need to design a CC/CP/CV converter using the current monitor (CM) feature of the LM5117 buck controller.

Application example

In the CC mode of operation, the output voltage increases as the load resistance increases, and as a result, the output power will increase linearly as the current is regulated into the load.  However some applications require the output current to be reduced as output voltage increases thereby limiting the power delivered to the load.  A relatively flat power limit over a wide output voltage range can be achieved with a simple modification to a CC/CV converter that uses the LM5117.

Method of implementing CC/CP/CV

Figure 1 shows a typical discrete implementation of a CC/CP/CV converter.  The difference between the CC/CV converter and the CC/CP/CV converter is the addition of a feedforward resistor (Rff).  

Figure 1 A typical discrete implementation of a CC/CP/CV converter

Output current regulation

The LM5117 has a CM pin. When the converter is operating in continuous conduction mode, the voltage on the CM pin (VCM_AVE) is proportional to the output current. By using a resistor divider from the VCM_AVE to ground and connecting the divider tap point to the feedback node of the LM5117, you can control the output current. Equation 1 expresses the relationship between the voltage on the CM pin and the output current:

Where Rs is the current sense resistor and As is the internal current sense amplifier gain.

The relationship between the voltage on the CM pin (VCM_AVE) and the voltage at the feedback node of the LM5117 (Vfb) is set by the resistor divider network and is expressed in equation 2.

Combining Equations 1 and 2 and rearranging for output current we can see how the output current is controlled by the feedback resistors from the CM to Vfb.  This is shown in Equation 3.

CP Programming

Rff is used to offset VCM_AVE as Vout varies by injecting a current into Vfb.  At higher output voltages , more current is injected into Vfb through Rff which reduces VCM_AVE.  As can be seen in equation 1, VCM_AVE controls the output current (Iout) and by reducing VCM_AVE, we reduce the regulated output current as the output voltage increases. Equation 4 calculates the voltage reduction (Voff_CM) at VCM_AVE:

Rff has a linear relationship with the output voltage and the output voltage has a linear relationship with Iout.  Because we are in effect summing into Vfb, the power limit over a given output voltage range will be nonlinear. 

As an example, given the requirements of a 60W power limit and an output voltage range of 6V to 12V, we can calculate the power stage components.   It is suggested the power stage components be selected for the highest Iout of 10A corresponding to the lowest output voltage of 6V with a power limit of 60W.  From our calculations, we determine Rs = 12mΩ and As = 8.5.  Note that the As of the LM5117 is reduced by external 200Ω series resistors at CS and CSG.  Refer to the LM5117 datasheet for more details on how series resistors connected to these pins reduces the current sense gain.

As a starting point, select values for RTop_CM and RBot_CM that will yield a maximum regulated output current 1.4 times greater than the specified regulated current of 10A, which occurs at the minimum output voltage. This suggestion is based on the fact that Rff will reduce VCM_AVE as described earlier and therefore reduce Iout.

For example, for a 60W power limit at a 6V output, multiply 10A by 1.4, which yields 14A of regulated output current. Select 10kΩ for RBot_CM and rearrange Equation 3 to calculate ~25kΩ for Rtop_CM. Select a standard value of 25.5kΩ for Rtop_CM.

Equation 5 calculates the amount of error introduced at the minimum Vout and serves as a good starting value for Rff:

With the addition of Rff at the minimum Vout, you need to ensure that this error is subtracted from VCM_AVE by making sure that the VCM_error is equal to the VCM_AVE. Make Equation 5 equal to Equation 4 and rearrange for Rff, as shown in Equation 6:

Evaluating Equation 6 yields an Rff = 167kΩ. Select a standard value of 155kΩ for Rff. Using Equation 4, calculate Voff_CM = 0.855V at a 6V output.

Equation 7 shows the resulting VCM_AVE, which is determined by subtracting Equation 4 from Equation 2:

For the given example here, VCM_AVE =1.985V

VCM_AVE controls the output current and this voltage decreases as the output voltage increases.  Equation 8 shows the relationship between the regulated output current (Iout_adj), VCM_AVE and Voff_CM.

Evaluating Equation 8 yields an Iout_adj = 10.053 at a 6V output.

Multiplying Equation 8 with the output voltage calculates the output power, shown in Equation 9:

Where

Evaluating Equation 10 calculates a Pout = 60.13W.

I recommend using Equations 7, 8 and 9 to check the power limit for a given output-voltage range to ensure that the power-limit profile suits the needs of your particular application. You can adjust Rff and RTop_CM to modify the power-limit profile for a given output-voltage range.

Figure 2 shows a plot of the power limit as voltage increases using the values from the example. As previously stated, the CP regulation is not precisely constant, but the power variation in this example is less than ±7% over the full operating range.

Figure 2: Power-limit curve as a function of output voltage

CV programming

Looking at Figure 1, the voltage-clamp circuit uses the LM4041 voltage reference. The LM4041 is unique when compared to other references in that its reference voltage Vfb is set between the LM4041’s cathode and reference pin as opposed to the anode and reference pin (cathode-referenced and anode-referenced voltage references, respectively). This is advantageous for this particular application because it minimizes the interaction between Rff and R1 during transition from CP to CV control.

Being cathode-referenced, the LM4041 allows the voltage reference to turn on without introducing errors during the transition. By using the LM4041, the end result is a small change in the output voltage as the converter changes from CP to CV regulation, which is solely based on the values selected for RTop_VC and RBot_VC.

Equation 11 sets the voltage clamp set point:

CC/CP/CV design of the LM5117

The design approach for the power stage of a CC/CP/CV converter using the LM5117 is the same as it is for a basic buck converter. I suggest carrying out the design at the highest output power level using either WEBENCH® Designer or the LM5117 Quick Start Calculator. You can also look at the LM5117 data sheet for guidance on the design of the buck power stage.

Example schematic

Figure 3 shows a 48V input, 60W power limit LM5117 from 6V to 12V, with an output voltage limiter (Vclamp) set to engage at 12.5V.

Figure 3: Example schematic for a 5V to 12V power limit of 60W and a voltage clamp set at 12.5V

Figure 4 shows the measured efficiency as a function of Iout.

Figure 4: Efficiency of the buck converter based on Figure 3

Figure 5 shows the measured power-limit profile as a function of the output voltage.

Figure 5: Power-limit profile

(I further reduced Rff to keep the power limit below 60W, selecting a final value of 150kΩ for Rff.)

Figure 6 shows the measured output voltage as a function of Iout. The converter’s sense resistor (Rs) sets the maximum current at the right side of the graph. Note that the value of Rs will affect the power-regulation variation.

Figure 6: Output-voltage variation as a function of Iout

Figure 7 shows the measured switch node (CH3), Vout ripple (CH1) and output current (CH4) at 48Vin, 6.6Vout at Iout > 8A.

Figure 7: Steady-state scope shots

Figure 8 shows the measured transient response at a 48V input voltage, with Vout (CH1), Iout (CH4) and a load step from 3.8A to 5.7A (0.1A/µs).

Figure 8: Transient response scope shots

Conclusion

The LM5117 configured as a CC/CP/CV converter provides a power-limit profile for an output-voltage range with the addition of an Rff resistor to a CC/CV converter. This design approach is relatively simple and provides advantages of reduced size, cost and power losses.

Ethernet adoption and adaptation by original equipment manufacturers (OEMs) and Tier-1 companies has been underway for several years now. Automotive-oriented amendments to the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard include IEEE 802.3bw (100BASE-T1, 100Mbps, copper) and IEEE 802.3bp (1000BASE-T1, 1Gbps, copper).

These amendments are important because they incorporated additional requirements and features specific to automotive that have been enabled the explosion of in-vehicle infotainment, advanced driver assistance systems, on-board diagnostics and connectivity to the outside world (5G, V2X).

The amendments primarily address the physical layer (PHY). The affected PHY interface is the electrical interface to the network, also known as the medium dependent interface (MDI). One of the key aspects of automotive-unique PHY specifications is MDI signaling, which addresses (EMI)/electromagnetic compatibility (EMC) and enables the use of unshielded single twisted-pair cabling on the network. This reduces cabling weight and cost – important factors in automotive.

Reduced weight and cost are not the only advantages for a connected vehicle. Ethernet facilitates a switched network, enabling improved bandwidth and higher data rates not possible in other shared bus topologies (Controller Area Network, Local Interconnect Network, FlexRay and Media Oriented Systems Transport).

The adoption of a switched network approach to in-vehicle communications brings many of the same constraints imposed on previous shared bus topologies, such as reliability, EMI/EMC, compliance with electrical interface specifications and functional compliance. The latter two items affect interoperability with other devices connected to the network. The number of network-connected in-vehicle sensors is growing and may be acquired from different suppliers, each using a different PHY (see Figure 1).

Figure 1: Distributed vehicle sensor network

Early on, several members of the automotive industry recognized the need to establish formal collaboration to address EMC/EMI and interoperability issues. The One-Pair Ether-Net (OPEN) Alliance (OA) special interest group (SIG) was established in 2011 and now includes over 300 members, including OEMs, suppliers and technology providers. The OA has guided both the development of the automotive-oriented amendments to Ethernet standards as well as PHY-oriented compliance test specifications to ensure threshold functionality and performance across components from different vendors, enabling the necessary reliability and ease of system integration that the automotive industry requires.

The OA compliance test specifications for PHYs cover three domains: EMC/EMI performance, functional and electrical conformance to the IEEE standard, and interoperability between PHYs from different vendors. The specific test specifications are:

• 100BASE-T1 EMC Test Specification for Transceivers.
• BroadR-Reach Physical Media Attachment Test Suite
•  BroadR-Reach PHY Control Test Suite
•  BroadR-Reach Physical Coding Sublayer Test Suite.
• 100BASE-T1 Interoperability Test Suite.

Collectively known as interoperability and compliance tests for 100BASE-T1 PHYs, these test specifications were developed by OA Technical Committee No. 1 (TC1). Together, they constitute the primary compliance tests technology suppliers must pass in order to demonstrate the threshold capability and performance that the standards require. They also give OEMs and suppliers tools for comparing PHYs.

TC1 commissioned a trio of independent labs to provide test services for the industry, each addressing one of the three domains. As a member of the OA, TI participates in this testing. For example, TI’s DP83TC811R-Q1 and DP83TC811S-Q1 have successfully passed each of the compliance tests at the independent labs, including interoperability. Interoperability testing assesses the device under test’s (DUT) compatibility with other link partners (LPs) under various operating scenarios, where the DUT may assume either a master or slave role in the system.

The functionality tested includes:

• The ability to link with multiple LPs within minimum required times under varying conditions, such as:
  • After hard or soft resets of either DUT or LP.
  • After entering sleep and after wakeup.
  • Temperature.
  • Cable lengths.
  • Injected noise.
  • Polarity.
• Sustaining the link once established.
• Link integrity, determined by frame loss indicators (cyclic redundancy check [CRC] errors, invalid packet size).
• Reliably indicating link status for valid link configurations and ensuring that false link indications are not triggered for invalid configurations.
• Feature sets such as signal quality indication and cable diagnostics (near end/far end, short/open).

Having successfully passed independent interoperability testing as well as EMI/EMC and PHY functionality testing, the DP83TC811R-Q1 and DP83TC811S-Q1 are fully qualified Automotive Electronics Council (AEC) Q-100 PHY for 100BASE-T1 (IEEE 802.3bw, BroadR-Reach) networks. These devices are fully supported by evaluation modules, an input/output buffer information specification (IBIS) model and software drivers.

Additional resources

• Check out the evolution of automotive networking white paper.
• Learn more about TI’s Ethernet PHY and other automotive interface solution portfolios.

Objects in the mirror are closer than they appear--this message is the tried and true safety warning that has reminded drivers for decades that their rearview mirrors are reflecting a slightly-distorted view of reality. Despite their limitations, mirrors are vital equipment on the car, helping drivers reverse or change lanes. But today, advanced driver assistance systems (ADAS) are going beyond a mirror’s reflection to give drivers an expanded view from the driver’s seat through the use of cameras.

Camera monitoring systems (CMS), also known as e-mirrors or smart mirrors, are designed to provide the experience of mirrors but with cameras and displays. Imagine looking into a rearview mirror display and seeing a panoramic view behind your vehicle. When you look to your side mirror, you see a high-resolution display showing the vehicles to your side. These scenarios are becoming reality, as are other features such as blind-spot detection and park assist.

It’s important to understand the current transition from mirrors to CMS. It’s no surprise that systems in today’s vehicles are already leveraging ADAS features for mirrors. Most new vehicles in the past decade have added a camera to the back of the vehicle or attached a camera to the existing side mirror, with a display inside the vehicle to give drivers a different perspective of what’s behind or at the side of the vehicle.

Figure 1 shows the routing of this rearview camera and display system. The backup display is embedded in the rearview mirror and a cable routes to the rear of the vehicle.

Figure 1: Rearview mirror display and rearview camera for panoramic or backup views

The side mirror is different because the camera is located on the mirror. The side mirror still exists for viewing, but typically its camera works when the driver activates a turn signal or shifts in reverse. During a turn or a lane change, the camera outputs a video feed to the infotainment display in the dashboard and may show a slightly different angle than the side mirror itself, as shown in Figure 2.

Figure 2: Side mirror with camera viewed on an infotainment display

Now that I’ve reviewed current CMS configurations that incorporate a mirror with a camera and display, it’s worth noting it’s possible to achieve a CMS rearview mirror replacement through the addition of one or two cameras installed on the rear of the vehicle.

From the rear of vehicle, video data from an imager is input to TI’s DS90UB933 parallel interface serializer or DS90UB953 serializer with Camera Serial Interface (CSI)-2. This data is then serialized over a flat panel display (FPD)-Link III coax cable to a DS90UB934 or DS90UB954 deserializer, and then output to an application processor for video processing, such as Jacinto^TM TDAx processors, and then shown on a rearview mirror display. If the display is located far from the Jacinto applications processor, you will need a display interface serializer and deserializer to route the data over a coax cable again. You could use the DS90UB921 and DS90UB922 red-green-blue (RGB) format serializer and deserializer, respectively, or, if you’re implementing higher-resolution displays, the DS90UB947 and DS90UB948 Open Low-Voltage Differential Signaling Display Interface (LDI) devices.

Figure 3 shows the connections between these devices when using a display onboard with an applications processor.

Figure 3: Rearview mirror system block diagram

The second CMS is the side mirror replacement portion. The camera must be located in the same location where the mirror used to be. This camera’s video data displays a view of what the driver would see in the mirror. To achieve this, the camera data is serialized and sent over an FPD-Link III coax cable to a remote display located in the upper part of the door panel or included in the rearview mirror display. With a camera and display, now the side view can be in more direct line-of-sight locations for the driver. For example, if both the displays for side view and rear view are included in the rearview mirror, the driver only needs to look in one location.

Another option available in a side mirror replacement is to add a second co-located camera with the first, but at a different viewing angle. The benefit of this setup versus a standard mirror is that with two differently angled cameras, one camera can be used for the view that a side mirror would have provided and the second camera can provide a wider field of view for blind-spot detection and collision warning features. Figure 4 shows a two-camera side mirror replacement system.

Figure 4: Side mirror replacement system block diagram

The question you may be asking now is why drivers need cameras and displays if they can achieve most of the same functionality with a mirror. The answer lies in the features that cameras can provide over mirrors alone. If only a side mirror exists, side collision avoidance is solely up to the driver. With a camera, the detection of a potential collision before a lane change could activate vehicle warning alerts that prevent drivers from making an unwise action. Panoramic rear views with wide field-of-view (FOV) rear cameras or a separate narrowly focused backup camera can provide a driver with different line of sights and reduces or eliminates blind spots that would not be possible with mirrors alone.

This is just the beginning, though, because in order for vehicles to move from driver assistance systems to autonomous systems, a CMS can be incorporated into sensor fusion systems. CMS has the opportunity to incorporate ultrasonics and possibly even radar. The fusion of rear and side cameras with ultrasonics adds the capability to assist drivers in parking or can even park the vehicle for them. Radars fused with side mirrors will add an extra measure of protection for changing lanes and even side collision avoidance.

To learn more about how to implement sensor fusion, check out the follow-up blog posts on park assist sensor fusion using CMS and ultrasonics or front sensor fusion with front camera and radar for lane departure warning, pedestrian detection and even assisted braking.

Additional resources

• Learn more about TI's ADAS reference designs. 
• Read the blog post, “Maybe hindsight can be better in 2020!”
• Read the white paper, “Stepping into next-generation architectures for multi-camera operations in automobiles”
• Peruse these reference designs:
  • Automotive 2-MP Camera Module Reference Design with MIPI CSI-2 Video Interface, FPD-Link III and POC.
  • ADAS Multi-Sensor Hub Reference Design with Quad 4-Gbps FPD-Link III, Dual CSI-2 Output and POC.

With process geometries of semiconductor technology declining to 10nm or below, designing the power supply for an industrial PC or single-board computer gets challenging like never before. In addition, the Industrial Internet of Things (IIoT) and Industry 4.0 are creating a stronger push toward smaller computing systems with increased performance. Figure 1 shows examples of supply requirements for some selected FPGAs with very low core voltages and very tight tolerances.

Figure 1: Supply voltage requirements for selected FPGAs (source: FPGA datasheets) 

Processors, field-programmable gate arrays (FPGAs) or system on chips (SoC)/application-specific integrated circuits (ASICs) using ultra-small process geometries offer very high functional integration and extreme performance levels, but they also require very high accuracy on their power-supply rails. Designing for 1.0V core voltages and below requires careful calculations of all DC specifications, as well as AC transients of corner spreads and process variations, to avoid false resets, unreliable operation or malfunction in single-board computer or industrial PCs.

Using 0.1% resistors to set the output voltage and adding multiple output capacitors can help fulfill the typical ±5% supply accuracy requirement even at very low voltages. But these resistors add cost and take up board space. Choosing a power supply with a 1% feedback voltage accuracy specification gives you more flexibility and potential cost reductions when selecting the output-voltage-setting resistor divider and output capacitors.

Figure 2 shows an example of the tolerance stack-up with a 1% reference voltage and 1% resistor accuracy, summing up to ±1.8% DC variations.

Figure 2: Target specification with 5% variation at a 1.0V core supply (source: Texas Instruments)

But you need to look at the details: not all 1% accuracy specifications are equal. Temperature variations and dependency on input voltages are common variables whose influences are sometimes not included in the 1% value. Some semiconductor suppliers show 1% accuracy on the first page of the data sheet. But this critical electrical parameter is often defined only at one given temperature and one input voltage point (for example, a 25°C room temperature and 3.6V input voltage).

TI’s new low-power TPS62147/TPS62148/TPS62135/TPS62136 (for 12V supply rails) and TPS62821/TPS62822/TPS62823/TPS62825/TPS62826 (for 5V supply rails) DC/DC buck converters can help solve the challenges that come with a 1% feedback voltage accuracy (or an output-voltage accuracy for fixed output-voltage options) specified over the full junction temperature range from -40°C to +125°C and over the full input voltage range of 3V to 17V or 2.4V to 5.5V. As well, these DC/DC converters are specified at very high output accuracy and offer very small solution size; for example: 1.5x1.5mm QFN for 2A or 3A (5V supply), or 2x3mm QFN for 2A or 4A (up to 17V supply).

For more information, visit TI’s new Power Management for FPGAs and Processors web page.

Additional resources

• Watch the video, “How to meet an FPGA’s DC voltage accuracy and AC load transient specification?”
• Check out the webinar, “How to Reduce the Total Size of FPGA Solutions.”
• Download the Small Efficient Flexible Power Supply Reference Design for NXP iMX7 Series Application Processors.
• Read the blog post, “Oh yes! My FPGA application is safe.”

A year ago, we released our first SimpleLink™ MCU software development kits (SDKs) with 100% application code portability across the industry’s broadest technology portfolio of wired and wireless MCUs.

With each quarterly release, we are committed to protecting your code investment while adding new capabilities to speed development and enable more opportunities for differentiation. Our first quarterly release of 2018 features updated tool-chain support including:

• Code Composer Studio™ software 8.0.0 with new Eclipse support.
• GNU Compiler Collection (GCC) version 7.
• IAR Embedded Workbench version 8.20.2 for Arm®.

Going forward, we plan to update the major version number in the first quarter of each year (which will often align with tool-chain and other major functionality improvements) and update the minor release number in subsequent quarters. Thus, the version for this 1Q release is 2.10. Our 2Q release will be version 2.20, 3Q will be 2.30 and 4Q will be 2.40. The 1Q 2019 release should be 3.10.

Version 2.10 includes several enhancements to the common components that form the foundation for the SimpleLink SDK. Those include an enhanced network services (NS) component with a set of cross-platform libraries that provide common services related to networking. The components of NS, as shown in Figure 1, include:

• SlNetSock, a TI-created abstraction layer for TCP/IP stacks and Transport Layer Security (TLS). SlNetSock enables users to create TLS-aware applications that aren’t bound to a particular network stack or security library. You can use the embedded TLS solution on CC3xxx devices, the mbed TLS-based TLS solution on MSP432E4 devices, or even bring your own TLS of choice, configured above the (nonsecure) SlNetSock application programming interfaces (APIs).
• Support for industry-standard Berkeley Software Distribution (BSD)/Portable Operating System Interface (POSIX) socket APIs.
• Higher-layer protocols, including HTTP client, Simple Network Time Protocol (SNTP) and Message Queuing Telemetry Transport (MQTT), with plans to add more soon.

Figure 1: Network services include the SlNetSock common socket layer

The MQTT library abstracts the underlying intricacies of a MQTT network and gives you intuitive and easy-to-use APIs to implement the MQTT protocol on SimpleLink devices. Examples are included to enable MQTT client connections to a cloud MQTT broker, as well as enabling a local MQTT broker that can serve as a gateway for local MQTT clients. A SimpleLink Academy module demonstrates use of the library.

Beyond connectivity, other new components include a graphics library that is now common across SimpleLink MCU devices. The library supports a number of primitives, shapes and buttons to simplify user interface and display designs. A new nonvolatile storage driver makes system designs with such components easier. FreeRTOS support has also been upgraded to support version 10.

The expanding foundation, when combined with a growing number of supported technologies – including recently announced Thread and Zigbee® support and expanded Bluetooth® 5 support – provides unsurpassed connectivity options in a code-compatible platform. Figure 2 lists the supported software technologies.

Figure 2: SimpleLink MCU SDKs feature a large and growing list of software technologies

Check out SimpleLink SDK version 2.10 today, and be sure to click the Alert Me button when you download a kit to be notified when each quarterly release is available.

Her influence was monumental. Her manner was unassuming. Her generosity was legendary. And her smile was unforgettable.

At 106, Margaret McDermott was the personification of purpose. She died Thursday, leaving a decades-long legacy of giving and community involvement.

“Today is a sad day – for Mary and me, for our Texas Instruments family around the world, for the Dallas/Fort Worth community, and for thousands whose lives have been touched by Margaret McDermott,” said Rich Templeton, chairman, president and CEO of Texas Instruments.

“Personally, Margaret meant so much to Mary and to me. She has been a true and loyal friend, beside us through good times and trying times. She has been TI’s staunchest advocate and coach, always believing in the great impact our company can make. In action and spirit, Margaret set an example we will always strive to emulate.”

Over six decades, Margaret, the wife of TI founder Eugene McDermott, gave tens of millions of dollars to better the lives of the people in her community. From championing education and basic needs to building hospitals, libraries, cultural art centers and more, Margaret made an indelible mark on the North Texas community.

“Margaret exuded warmth and compassion for everyone she met, and had an understated grace and generous spirit that came from a lifetime rich with experience and hard work,” said Mary Templeton, Margaret’s longtime friend and wife of Rich Templeton.

“Margaret and her late husband, Eugene – a TI founder – demonstrated a deep commitment to to the community,” said TIer Terri Grosh. “From TI’s early days, they inspireda spirit of giving back. Their commitment to the community helped instill those very same values in TI as a company. The McDermott legacy has strongly influenced our culture and many decades of community service from TIers around the world.”

“We owe what we understand and know and do about philanthropy to Margaret,” said Terri West, retired TIer and chair of the TI Foundation board. “She led generations of new TIers to understand the importance and the impact of philanthropy.”

To honor Margaret and all she’s done for TI and Dallas, the TI Foundation recently created a community impact award and three fellowship programs. The first community impact award will be given this year to TIers who have embodied the spirit of giving. The TI Founders Leadership Fellows program provides three annual nonprofit work experiences to university or graduate students planning a nonprofit career. Designed to build a pipeline of nonprofit leaders in the Dallas area over the next 20 years, the fellowships were established in collaboration with three local organizations that Margaret loved and blessed with her generosity – the Dallas Museum of Art, the University of Texas at Dallas and the United Way of Metropolitan Dallas.

Destined for greatness

Margaret’s family came to Texas in 1829. A native Dallasite, she was born Margaret Milam on Feb. 18, 1912. She lived through the Great Depression and worked in the 1930s as society editor for The Dallas Morning News, covering debutante balls and charity events. As a society reporter, Margaret regularly attended balls in Dallas. At one such ball in the late 1930s, she was escorted by O’Neal Ford, a famous architect. It was on this special evening that she met geophysicist Eugene “Gene” McDermott, president of the Petroleum Club and a co-founder of Geophysical Service, Inc. (GSI), which went on to become Texas Instruments in 1951.

It was not until many years and experiences later that she would reconnect with Gene.

Margaret left the society pages behind her and went on to cover World War II from India and worked for the American Red Cross in India, Germany and Japan during and after the war.

In 1943, Margaret applied and was accepted as a U.S. Army civilian in the American Red Cross, with her first assignment in Tezpur, the northern Indian province of Assam. By the end of the war, she applied and was accepted for a position in Germany, where she lived from 1946 to 1948. It was “a country in ruins, total defeat,” she wrote.

Not ready to return home, Margaret then moved to Japan, where she lived on a small island across from Hiroshima Bay in 1948-49. Her time in India, Germany and Japan during the war and its aftermath birthed in Margaret an “international longing for peace,” she wrote.

It was concern for her parents that brought Margaret back to Texas, where she re-met Gene when she interviewed him for a story.

He asked her out to dinner.

“Through that connection and seeing her at different events around town, he took a liking to her,” said Max Post, a retired TIer, who visited Margaret at her home in 2004 when he was doing research for a book about TI called Engineering the World.

Gene and Margaret married in 1952. For their honeymoon, they travelled around the world to visit TI sites, Max said.

“It was like a work thing,” he said. “That sounds like a TIer – taking your wife on a honeymoon trip to visit the operations. Thoughtfully, he took her to London and Paris on the way, which they enjoyed.”

Two years after their marriage, Gene and Margaret bought the ranch in Allen where they lived for many years. Among her regular visitors was one of her dear friends, Claudia Alta “Lady Bird” Johnson.

“Allen was a small town at the time,” Max said. “One day, a neighbor near the ranch called the police in the city of Allen to report that a very strange helicopter was hovering over the ranch and had come frequently. They suspected suspicious activity. But it was Lady Bird Johnson coming to visit Margaret McDermott and talk about Texas wildflowers and see what she had done at the ranch.”

Foundation of giving

Gene and Margaret founded the Eugene McDermott Foundation in 1955. Their daughter, Mary McDermott Cook, is now the president.

In 1961, Gene McDermott partnered with J. Erik Jonsson and Cecil Green – also co-founders of TI – to establish the Graduate Research Center of the Southwest, later renamed the Southwest Center for Advanced Studies, in Richardson. Created as a facility for students to complete their doctoral work and continue research, the center became part of the University of Texas system in 1969 and was renamed the University of Texas at Dallas (UTD).

“Early on, TI recognized that to hire technical talent and keep them in Dallas, they needed a first-class research university,” Max said. “So they started working with what we had here. There didn’t seem to be a lot of support at the time from other universities stepping up in that area. So they said, ‘We’re going to have to do it ourselves if we really want to do this.’ They just stepped up and did it.”

The McDermotts, the Greens and the Jonssons bought several hundred acres and donated it to the university.

“In the beginning, it was this little building with a transmitter tower,” said Sam Self, a retired TIer and former chairman of the TI Foundation Board, who now serves as a trustee of the Eugene McDermott Foundation. “Gene took Mrs. Mac up there to see the land, and she said, ‘This is the ugliest piece of land I’ve ever seen in my life.’ It was flat as it could be – all cotton fields. There were no native trees, nothing. A few years ago Mrs. Mac, as she’s often called by friends, donated a painting from her vast art collection to fund Peter Walker, the landscape architect who designed the Nasher Sculpture gardens, to beautify the grounds at UTD.

“Now, when you drive onto that campus, there is a winding road, native trees, and beautiful magnolia trees leading to the central courtyard. All of that was done because Mrs. Mac wanted to beautify the grounds.”

In 2000, Margaret made the largest private gift in UTD’s history, $32 million, to establish the Eugene McDermott Scholars Program. 

The program is one of the most selective and generous undergraduate merit awards in the nation. It has benefitted more than 350 recipients since it was established, and covers all costs for some of the best and brightest students in the country – including costs to study abroad.

“The McDermott name is synonymous with giving back,” said Peter Balyta, president of TI Education Technology and vice president of Academic Engagement and Corporate Citizenship. “The University of Texas at Dallas, my alma mater, was one of her passions since her husband co-founded it in 1961. From the many professorships and scholarships she endowed there, to her steadfast support for science and engineering programs, Mrs. McDermott significantly advanced the cause of STEM education in North Texas for generations to come.”

Margaret’s devotion to advancing education could be seen throughout her life – from the time she was a founding trustee for the Dallas County Community College District to the endowed positions she supported at St. Mark’s School and Hockaday. Other educational institutions that have benefited from Margaret and the Eugene McDermott Foundation’s gifts include the University of Dallas, the University of Texas Health Science Center, Southern Methodist University and University of Texas Southwestern Medical Center.

Gene and Margaret’s long legacy of giving at UT Southwestern Medical Center can be seen not only in the buildings and grounds, but in the physicians who practice, research and teach there.

“Margaret’s passion for supporting the basic needs of our communities – including health and education – helped shape the landscape of Dallas,” Rich said. “Her countless contributions and generosity were an inspiration and have made a tremendous impact that will last for generations to come.”

In addition to championing community needs, Margaret’s love for arts and culture was legendary. She served as board president of the Dallas Museum of Art from 1962-64 and later was chairman of the board and chairman of acquisitions in the 1970s.

“Art brought Margaret great joy, and she wanted that joy to be experienced by others,” said Jennifer Sampson, McDermott Templeton President and CEO of United Way of Metropolitan Dallas. “I heard her tell stories about how her love for art began with the travels she went on with Gene. They would learn about arts and culture all over the world, and she would bring that knowledge back to influence the culture of arts in Dallas. Many of the pieces of art the DMA has today are from Margaret’s own collection.”

In her yet-to-be-published book, Margaret wrote about the influence of art in her life:

“Art took us around the world, and brought the world to us. The collectors we met, the dealers we relied upon, the visitors we welcomed into our home, and the artists we loved all became part of our world in Dallas.”

Additional arts and culture organizations supported by the Eugene McDermott Foundation include the Meyerson Symphony Center, the Winspear Opera house, the Dallas Symphony Center, the Dallas Arboretum, the Dallas Zoo, the Lady Bird Johnson Wildflower Center and the Dallas Center for Performing Arts.

Each of the categories Margaret supported was close to her heart, Sam said.

“With all of these things that she did, it was about making people’s lives better,” Sam said. “More beautiful, healthier, more educated. Better.”

‘More active than most’

After six decades of devoted philanthropy, Margaret remained a member of the Eugene McDermott Foundation board through her last years, and frequently supplemented foundation gifts with her own personal funds, Sam said. Margaret also frequently spoke of her deep and abiding love for TI -- and said all of her philanthropy would not have been possible without TI.

Margaret was always interested in people. Frequently at charity dinners, Sam would sit next to Margaret. “At some point, Mrs. Mac would tap on her glass and say, ‘Let’s go around the table and talk a little bit, and why don’t we start with you. Tell us a little about yourself.’ And she would go to every person. She genuinely wanted to know about the people around the table.”

The quality Sam admired most about Margaret was not just her generosity, he said, but her graciousness.

Challenging others to think differently

Anyone who spent time with Margaret would be challenged to think differently about the community we live in, said Mary.

“Margaret is still making a difference every day. Her ability to identify and develop people who could make an impact in the community was inspiring,” Mary said.

One of the ways Margaret did this was to invite people to her home.

“A lunch with Margaret was never about the food,” she said. “With Margaret, every lunch had a purpose.”

At one such lunch, Margaret had invited Mary and her husband, Rich, and former TI CEO Tom Engibous and his wife, Wendy.

“After a few pleasantries, discussing wildflowers and life in the community, the lunch quickly turned serious over a glass of wine,” Mary said. “Margaret wanted lunch at the Winspear to discuss the symphony. She wanted us to have lunch with the new DMA president to review her permanent collection. She wanted to discuss the J. Erik Jonsson Central Library in downtown Dallas, which needed more funding. And she gave us a summary of her opinion of the new TI board members, who were lovely.”

The list of things that needed to be addressed was lengthy, said Mary, who took notes to capture actions that needed to be taken following the meal.

Margaret’s “lunches with purpose” influenced the grants she made, both through the Eugene McDermott Foundation and out of her own money, Sam said.

It is fitting, Sam said, that Margaret’s name is now permanently attached to Margaret McDermott Bridge, a structure that brings beauty and interesting curves and architectural significance to a Dallas skyline that was once very angular and square.

“Had they told her that they wanted to name the bridge for her, I know what she would have said. ‘No, and no, and no,’” Sam said. “But they named it for her, and I think it is the most appropriate thing. Mrs. Mac enjoyed looking at that beautiful structure, even though there were five people whom she would have named it after instead of her.”

While the lion’s share of her philanthropic gifts occurred in Dallas and surrounding areas, Mrs. McDermott’s influence reached far beyond institutions of brick and mortar to the hearts of countless people she inspired to do more – to do better. From people she met along her many travels to those who gave back alongside her – to the students and former students who owe the breadth of their education to her – Mrs. McDermott’s impact will continue to spread from person to person, around the world, through the people she has touched and the people they will touch.

This is the first in a three-part series on optical heart rate sensors for biometric wearables. This first installment focuses on how these sensor systems work and what you can measure with them.

Most wearables use photoplethysmography (PPG) to measure heart rate and other biometrics. PPG is the methodology of shining light into the skin and measuring the amount that scatters based on blood flow. That’s an oversimplification, but optical heart-rate sensors work based on the fact that light entering the body will scatter predictably as the blood-flow dynamics change, such as with changes in blood pulse rates (heart rate) or changes in blood volume (cardiac output). Figure 1 below depicts the primary components and basic working methodology of an optical heart rate sensor.

Figure 1: Optical heart rate sensor’s basic structure and operation

Optical heart-rate sensors use four primary technical components to measure heart rate:

• Optical emitters – generally comprising at least two light-emitting diodes (LEDs) that send light waves into the skin.
• A photodiode and analog front end (AFE) – these components capture the light refracted from the wearer and translate those analog signals into digital signals for calculating meaningful heart-rate data. After evaluating all AFE options on the market, Valencell selected the TI AFE4410 in its next-generation Benchmark sensor system.
• Accelerometer – the accelerometer measures motion and is used in combination with the light signals as inputs into PPG algorithms.
• Algorithms – the algorithms process the signals from the AFE and accelerometer into a PPG waveform, which can generate continuous, motion-tolerant heart-rate data and other biometrics.

What can an optical heart-rate sensor measure?

Optical heart-rate sensors produce a PPG waveform that can measure heart rate as a foundational metric, but there’s much more that can be measured from a PPG waveform. Although it is very difficult to achieve and maintain accurate PPG measurements (more on that in the next section), when you do get it right, it can be very powerful. A high-quality PPG signal is foundational to a wealth of biometrics that the marketplace is demanding today. Figure 2 is a simplified PPG signal marking the measurement of several biometrics within that signal.

Figure 2: Typical PPG waveform

Here’s further detail on some of the measurements possible with optical heart rate sensors:

• Breathing rate – lower resting breathing rates generally correlate with higher levels of fitness.
• VO₂ max – VO₂ measures the maximum volume of oxygen someone can use and is widely considered an indicator of aerobic endurance.
• Blood oxygen levels (SpO₂) – blood oxygen levels indicate the concentration of oxygen in the blood.
• R-R interval (heart-rate variability) – The R-R interval is the time between blood pulses; generally, the more varied the time between beats, the better. R-R interval analysis can be used as an indicator of stress levels and various cardiac issues.
• Blood pressure – it is now possible to measure blood pressure without a cuff using PPG sensor signals. Here’s a link to a demo of Valencell’s technology measuring blood pressure.
• Blood perfusion – Perfusion refers to the body’s ability to move blood through the circulatory system, particularly in extremities and in the capillary beds throughout the body. Because PPG sensors track blood flow, it’s possible to measure blood relative blood perfusion and changes in blood perfusion levels.
• Cardiac efficiency – this is another indicator of cardiovascular health and fitness that typically measures how efficiently the heart works to take one step.

Optical Heart Rate Sensor Challenges

Designing an optical heart-rate sensor can be very challenging on a wearable device, because the methodology is sensitive to motion. To compensate, you need to have strong optomechanics and signal-extraction algorithms. Figure 3 shows some of the primary challenges you might face when designing with optical heart rate sensors. 

Figure 3: Primary challenges when integrating optical heart rate sensors

Optomechanics

Here’s further detail on the optomechanical considerations for PPG sensor integration:

• Optomechanical coupling – is light guided and coupled to and from the body effectively in the device? This is critical to maximize the blood-flow signal and minimize environmental noise (such as sunlight) that can add noise to the sensor.
• Are the right wavelengths being used for the body location? Different wavelengths are required, in part because of the different physiological makeup of the body at different locations and because of the impact of environmental noise at different locations.
• Does the design use multiple emitters and are they spaced apart correctly? The spacing of emitters is important in order to ensure that you are measuring enough of the right kind of blood flow and fewer motion artifacts.
• Are the mechanics such that displacement between the sensor and the skin is minimal during exercise or body motion? This can be a problem for many common wearable activities, such as running, jogging and gym exercises.

Signal-extraction algorithms

Here’s further detail on the signal-extraction considerations for PPG sensor integration:

• Have the algorithms been validated on a diverse population set? It’s important to make sure that the device works on multiple skin tones, both genders, different body types and fitness levels, etc.
• Are the algorithms robust against multiple types of motion noise? The algorithms must be able to work during different activities, including walking, running (high-speed steady runs and interval training), sprinting, gym workouts, and everyday life actions like typing or riding in a vehicle.
• Are the algorithms continually improving to handle more use cases and new biometrics? This technology and the wearables market are advancing rapidly and you must continue to innovate to meet ongoing customer requirements.

I hope this post provided some insight on how PPG sensor systems operate and what they can measure. In the next post in this series, I’ll explore best practices in integrating this technology into devices of all kinds – watches, fitness bands, earbuds and more.

Additional resources

• See TI’s photodiode sensing portfolio.
• Find resources and reference designs for wearables here. 

As shown in Figure 1, a very basic transmission system for an electric vehicle (EV) comprises three system blocks.

• The battery pack is an array of cells (typically lithium-ion [Li-ion] cells in full automotive EVs) that generates voltages up to hundreds of volts. The system needs of the EV will define the voltage.
• The next part of the system is the inverter. EVs use AC traction motors because they provide affective acceleration from a complete stop and are also very reliable. Voltage from the battery pack is in the form of DC; this is converted into AC (typically three phase) through the inverter. Like the voltage, the number of phases depends on the needs of the system and the type of motor used, but there are typically three phases.
• The electric motor is usually an induction motor, which requires an AC voltage. These types of motors are common in EVs because they are easily driven, reliable and cost-effective. The motor comprises three coils wound around an outer part called the stator. The inner portion is typically a cage made up of copper or aluminum rods called the rotor. 

Figure 1: Simple flow of an EV transmission chain – BMS goes to Inverter then to 3 phase AC Motor

In this blog, I will talk about considerations related to the battery pack and managing state of charge. Because the battery pack is made up of multiple cells connected in series, its effective usability is based on the weakest battery cell. The cell charges differ because of different chemical imbalances that occur during manufacturing, position in the pack (where heating varies), and changes related to usage or longevity.

The difference between cell voltages indicates an unbalanced cell at the system level. The reasons for the differences are still being studied even now. Understanding this well is an important goal, because it affects how long the battery pack will last in terms of power output, as well as the usable life of each individual cell and the lifetime of the battery pack.

One of the most important parameters to consider is state of charge. This is the different amount of charges contained in the individual cells. The amount of imbalance between the cells is measured in percentage. So if one cell has a 94% state of charge and another has 88% state of charge, there is an imbalance of 6%. Each cell will also have a different voltage called the open circuit voltage (OCV), which is the chemical state of charge.

The challenge for a battery pack is that when drawing current, not every cell will lose charge at the same rate. So discharge rates happen at different rates, even though the cells are connected in series. Because some cells sink lower than others, their ability to recycle and absorb the amount of charge will change over time. This cycle is accelerated by other conditions, including temperature. As I mentioned earlier, some cells might be hotter in the pack simply by their position or location near cooling elements.

The main cause of cell failure is having the cell collapse completely, which will affect the battery voltage because the cell is essentially just a resistance lowering the voltage. One way to prevent this is through cell balancing, which is the process of managing how to bring each cell up to a full charge. There are several techniques that can accomplish cell balancing; the simplest is to put a resistor and a metal-oxide semiconductor field-effect transistor (MOSFET) in parallel with each cell, monitoring the voltage across the cells via a comparator that watches the voltage and using simple algorithms to turn on the MOSFET to bypass the cell. The disadvantage of this approach is that the bypassing wastes energy.

Another technique is known as charge shuffling, which doesn’t use resistors and only a capacitor is connected between the cells. This technique does not waste energy in the bypassing, but it is more complex, because you need to connect over wider distances between the cells, rather than bypassing each cell individually.

The technique used in EVs is generally inductive charging, where a transformer connects between cells that are imbalanced because it is a higher power system. The circuit design tends to be quite large, which requires larger area within the design to accommodate the amount of circuitry required to implement the solution.

All of this balancing is based on extensive research into individual cell characteristics and chemistry, represented by spreadsheets and mathematical formulas that use tools like MATLAB to run them. A microprocessor plays an important part in the system by making sure that all balancing executes correctly. To power the microprocessor, the system supplies power from a DC/DC converter, which connects directly to the battery pack and provides either a 48V or 12V output based on the system design. Texas Instruments has two devices that can power the microprocessor; both have the ability to withstand tough conditions in terms of transient performance, along with wide voltage ranges.

The LM5165-Q1 is a 3V to 65V, ultra-low Iq synchronous buck converter with high efficiency over a wide input voltage and load current ranges. With integrated high- and low-side power MOSFETs, this device can deliver up to 150mA of output current at fixed output voltages of 3.3V or 5V, or an adjustable output. The converter is designed to simplify implementation while providing options to optimize the performance of applications like battery-management systems. Working up to 150°C Tj, the device can withstand the high operating temperature ranges found in EVs.

The LM46000-Q1 SIMPLE SWITCHER® regulator is a synchronous step-down DC/DC converter capable of driving up to 500mA of load current from an input voltage range of 3.5V to 60V. The LM46000-Q1 provides exceptional efficiency, output accuracy and dropout voltage in a very small solution size when you need a high input voltage or more current from the system.

There are many ways to manage balancing of Li-ion cells in a pack but how the design looks can depend on many factors, like cost, size, heat and needed accuracy. It is important to consider all these factors in the design strategy before implementation. Get more information about TI’s products which meet strict automotive and system requirements, and view a system block diagram for a HEV high cell count battery pack.

The robustness and reliability of a self-driving car’s computer vision system has received a lot of  news coverage. As a vision software engineer at TI helping customers implement advanced driver assistance systems (ADAS) on our TDAx platform, I know how hard it is to design a robust vision system that performs well in any environmental condition.

When you think about it, engineers have been trying to mimic the visual system of human beings. As Leonardo DaVinci said, “Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature, because in her inventions nothing is lacking and nothing is superfluous.”

Indeed, I was recently painfully reminded of this fact. On March 2, 2018, I caught an eye infection which was eventually diagnosed as a severe adenovirus. After a month, my vision is almost back to normal. Throughout my health ordeal, I learned a few things about the human visual system that are applicable to our modern-day challenge of making self-driving cars.

The importance of sensor redundancy

The virus affected my right eye first, and the vision in that eye became very blurry. When I had both eyes open, however, my vision was still relatively good, as though my brain was selecting the image produced only by my left eye but using the blurry image produced by my right eye to assess distance. From this, I can infer that stereo vision doesn’t need to operate on full resolution images, although of course that is optimal. A downsampled image and even a reduced frame rate should be OK.

When my right eye became so painful I could no longer open it, I had to rely on my left eye only. Although my overall vision was still OK, I had difficulty assessing the distance of objects. During my recovery, my right eye started healing first, and my brain did the same thing once more: it relied on the eye that was improving.

From these observations, I can draw these conclusions about autonomous driving: for each position around the car where vision is used for object detection, there should be multiple cameras (at least two) pointing to the line of sight. This setup should be in place even when the vision algorithms only need monovision data.

Sensor multiplicity allows for failure detection of the primary camera by comparing images with auxiliary cameras. The primary camera feeds its data to the vision algorithm. If the system detects a failure of the primary camera, it should be able to reroute one of the auxiliary cameras’ data to the vision algorithm.

With multiple cameras available, the vision algorithm should also take advantage of stereo vision. Collecting depth data at a lower resolution and lower frame rate will conserve the processing power. Even when processing is monocamera by nature, depth information can speed up object classification by reducing the number of scales that need processing based on the minimum and maximum distances of objects in the scene.

TI has planned for such requirements by equipping its TDAx line of automotive processors with the necessary technology to handle at least eight camera inputs, and to perform state-of-the-art stereo-vision processing through a vision accelerator pack.

The importance of low-light vision, reliance on an offline map and sensor fusion

After the virus affected both of my eyes, I became so sensitive to light  I had to close all the window blinds in my home and live in nearly total darkness. I managed to move around despite little light and poor vision because I could distinguish object shapes and remember their location.

From this experience, I believe low-light vision processing requires a mode of processing different than the one used in daylight, as images captured in low-light conditions have a low signal-to-noise ratio and structured elements, such as edges, are buried beneath the noise. In low-light conditions, I think vision algorithms should rely more on blobs or shapes rather than edges. Since histogram of oriented gradients (HOG)-based object classifications rely mostly on edges, I expect they would perform poorly in low-light conditions.

If the system detects low-light conditions, the vision algorithm should switch to a low-light mode. This mode could be implemented as a deep learning network that is trained using low-light images only. Low-light mode should also rely on data from an offline map or an offline world view. A low-light vision algorithm can provide cues in order to find the correct location on a map and reconstruct a scene from an offline world view, which should be enough for navigation in static environments. In dynamic environments, however, with moving or new objects that were not previously recorded, fusion with other sensors (LIDAR, radar, thermal cameras, etc.) will be necessary in order to ensure optimum performance.

TI’s TDA2P and TDA3x processors have a hardware image signal processor supporting wide-dynamic-range sensors for low-light image processing. The TI Deep Learning (TIDL) library implemented using the vision accelerator pack can take complex deep learning networks designed with the Caffe or Tensor flow frameworks and execute them in real time within a 2.5W power envelope. Semantic segmentation and single-shot detector are among the networks successfully demonstrated on TDA2x processors.

To complement our vision technology, TI has been ramping efforts to develop radar technology tailored for ADAS and the autonomous driving market. The results include:

• Automotive radar millimeter-wave (mmWave) sensors such as the AWR1xx for mid- and long-range radar.
• A software development kit running on TDAx processors that implements the radar signal processing chain, enabling the processing of as many as four radar signals.

The importance of faulty sensor detection and a fail-safe mechanism

When my symptoms were at their worst, even closing my eyes wouldn’t relieve the pain. I was also seeing strobes of light and colored patterns that kept me from sleeping. My brain was acting as if my eyes were open, and was constantly trying to process the incoming noisy images. I wished it could detect that my eyes were not functioning properly and cut the signal! I guess I found a flaw in nature’s design.

In the world of autonomous driving, a faulty sensor or even dirt can have life-threatening consequences, since a noisy image can fool the vision algorithm and lead to incorrect classifications. I think there will be a greater focus applied to developing algorithms that can detect invalid scenes produced by a faulty sensor. The system can implement fail-safe mechanisms, such as activating the emergency lights or gradually bringing the car to a halt.

If you are involved in developing self-driving technology, I hope my experience will inspire you to make your computer-vision systems more robust.

Additional resources

• Read these white papers:
  • “Stereo vision – Facing the challenges and seeing the opportunities for ADAS applications.”
  • “AWR1243 sensor: Highly integrated 76-81GHz radar front end for emerging ADAS applications.”
  • “Embedded low-power deep learning with TIDL.”
  • Order the processor software development kit for TDAx ADAS systems on chip with Linux® and TI real-time operating system (RTOS) support.
  • Learn more about TI’s ADAS solutions

Dear Bluetooth,
I can’t believe 20 years have passed,
You’ve made an impact that’s here to last!

As a thank you for all that you do,
Here are 20 things to love about you:

1. Wireless mice. It’s the little things we take for granted. Having a portable mouse for your laptop wouldn’t be possible without Bluetooth.

2. Wireless keyboards. Similarly, most tablets today aren’t complete without a handy keyboard that attaches without a cable.

3. Smartphones. This might be the biggest reason to love Bluetooth: it’s in every smartphone, making Bluetooth technology ubiquitous and disruptive.

4. Bluetooth speakers. No beach day is complete without this essential item, making it easy to enjoy your favorite tunes wherever you are.

5. Wireless earphones. Remember when it was the norm to spend five minutes untangling the knots in your wired earbuds? It’s safe to say that once you go wireless, you never go back!

6. Mobile printing. What a convenient luxury to print documents straight from your smartphone.

7. Hands-free calling. A new car isn’t complete without a state-of-the-art infotainment system enabling you to keep two hands on the wheel while making a phone call.

8. Car audio streaming. Streaming your favorite playlist through your car speakers is a necessity for any good road trip!

9. Fitness trackers. Bluetooth created a new buzz with the ability to seamlessly track your steps and log your sleep, challenging you daily to live a heathier lifestyle.

10. Smartwatches. To continue the pace, Bluetooth-enabled smartwatches track workouts, activities and monitor heart rates – definitely a step up!

11. Electronic smart locks. Whether it’s realtor lock boxes, hotels or your own front door, the smart lock gives you the power to control entrances from your phone.

12. Gaming consoles. From handsets to virtual reality goggles, Bluetooth has taken gaming to a whole new level.

13. Blood glucose monitors. Aiding the lives of many around the world, we send sincere thanks to Bluetooth for making it easier to track glucose readings for individuals and caretakers.

14. Patient monitors. Being hooked up to fewer machines is always a good thing. Wireless patient monitors enable doctors to monitor vitals without any extra wires.

15. Asset tracking. The perfect solution for those who habitually misplace their keys, now there’s really no excuse for you being late to that 8 a.m. meeting.

16. Stadium beacons. Always looking for the nearest concession stand at a stadium? Bluetooth beacons can easily guide you to your favorite fan fare.

17. Airport beacons. A new trend that sets your mind at ease while traveling, with turn-by-turn navigation to airport gates and baggage claim.

18. Retail coupons. Need someone to blame for buying the buy-one-get-one-free potato chips? Bluetooth can turn an innocent trip down the junk food aisle into a purchase by sending an irresistible coupon straight to your smartphone.

19. Baby monitors. Making a big impact on the lives of little ones, smart baby wearables help you ensure that your baby isn’t running a fever and is sound asleep.

20. Smartphone as a car key. Bluetooth is driving a big change in making it easier to access cars and control vehicle settings from your smartphone.

The list could go on and on, but it’s safe to say Bluetooth has made a big impact.
Happy 20th anniversary Bluetooth!

For more information, see www.ti.com/ble.

NXP QorIQ processors are high-performance 64-bit Arm® multicore processors for cloud networking and storage applications. Two of the high-end QorIQ variants are the LS2085A and LS2088A.

There are several power-supply rails required on an LS2085A/2088A board: the most important are the core rail and the SerDes logic and receiver rail. Using the PMBus interface eases the programming and monitoring of these high-current rails.

TI offers the PMBus Voltage Regulator Reference Design for NXP QorIQ LS2085A/88A Processors, which fully meets LS2085A/88A tolerance specifications while requiring only 50% of the output capacitance necessary on NXP evaluation boards. The reference design consists of the TPS53681 dual-output PMBus controller and TI’s CSD95490Q5MC smart power stages, as shown in Figure 1.

Figure 1: NXP LS2085A88A QorIQ power design

TI fully tested this reference design, and the board includes onboard load-transient generator circuits to test load transients and thus measure the AC output-voltage tolerance. The reference design board has all of the connections for complete power-supply testing, as well as programming of the TPS53681 and monitoring of the two voltage rails through the PMBus interface using TI’s Fusion Digital Power™ Designer (Figure 2).

Figure 2: NXP LS2085A88A QorIQ power design evaluation board

Among the many tests are the important load-step and load-release transient tests, as shown in Figures 3 and 4. In both cases, the reference design meets the NXP tolerance specifications.

Figure 3: NXP LS2085A88A QorIQ load-step test

Figure 4: NXP LS2085A88A QorIQ load-release test

The design even includes a Nyquist plot on top of the Bode plot to prove design stability, as shown in Figure 5. The Nyquist plot is stable if no encirclements (circle wrapping around) of the point (–1, 0) occur as the test frequency is swept during testing.

Figure 6: VDD rail power-stage temperatures, 60A load (left); GVDD power-stage temperatures, 30A load (right)

NXP processors are now part of TI’s power for processors portal, which will be updated with TI power solutions and designs for additional NXP networking processors. So if you are designing with NXP QorIQ processors and don’t know where to start, TI has made it easy to design using the LS2085A/88A QorIQ design and get ahead of the competition with our easy-to-use power selection and design tools.

Additional resources

• Read the blog post, “Power Tips: How to use Nyquist plots to assess system stability.”
• Download the LS2085A/88A QorIQ TI Design Guide.

With the highly anticipated ratification of the latest Power over Ethernet (PoE) standard, Institute for Electrical and Electronics Engineers (IEEE) 802.3bt, an increasing number of applications are considering PoE as their power delivery technology of choice. Historically, on the load (also referenced to as the Powered Device or PD) side of the cable, PoE has been very popular with Internet protocol (IP) surveillance cameras, wireless access points, IP phones, and small home and office routers. A new application, PoE connected lighting, is garnering a lot of attention and consideration.

PoE is not currently an option in today’s light-emitting diode (LED) lighting ballasts for two reasons.

First, given the absolute power limit of the current IEEE 802.3at standard, PoE could only deliver 25.5W at the end of 100m of standard Ethernet cable, thus limiting the lumens generated from a PoE-based system and prohibiting its use for smart building use cases. The upcoming IEEE 802.3bt standard – expected to publish in late summer 2018 – eliminates this issue. With the new standard, power delivered to the PD can achieve 71W, which will meet the demands for many of the most popular LED ballast models available today.

Second, standby power is a critical consideration for connected lighting. Unlike a traditional light luminaire with a hardware switch, intelligent LED ballasts are usually powered even when the light is off. Having the sensors and other intelligence remain on while the luminaire is off enables fast turn-on.

Reducing overall power consumption is a major selling point for intelligent LED ballasts, making it critical to keep standby power as low as possible. Today, the minimum maintain power signature (MPS) overhead budget is ~115mW (calculated as 50V x 10mA x 75ms/75ms + 250ms) at a V_IN of 50V. Most designs will need to add margin to the MPS current and duty cycle to compensate for integrated circuit tolerance and noise. Thus, a typical design following the IEEE 802.3at standard will likely consume 150mW-200mW of power. This may not seem a big deal, but larger installations have hundreds or even thousands of lighting fixtures. It adds up fast!

The new IEEE 802.3bt standard can achieve significant improvements in standby power consumption. Using the Connected LED Lighting IEEE802.3bt Power Over Ethernet (PoE) Reference Design, the entire standby power consumption is just 181mW (see Figure 1). This includes all of the operation required during standby (powered device, microcontrollers [MCU], physical layer [PHY], media access control [MAC], etc.). It’s easy to see why lighting manufacturers are excited about the new MPS specification in the upcoming IEEE 802.3bt standard. When combined with an optimized design, the MPS specification significantly helps minimize standby consumption and reduce the carbon footprint.

Figure 1: Input power consumption in standby (lights off)

Of course, some may question the value of PoE-connected lighting beyond these straightforward power demand and overall system-efficiency calculations. What about cost? According to one lighting solution provider, installation costs can be reduced by as much 25% and commissioning costs by as much as 50% when installing PoE-based networks.

As for end-user value, connected lighting brings many exciting new features, including customized brightness and color control; activity tracking/people counting; and visible light communication (VLC), which ultimately enables indoor positioning systems.

Early feedback on adding PoE to connected LED lighting ballasts is positive and gaining momentum. TI’s TPS2372-3 and TPS2372-4 PoE powered devices were developed specifically for such applications.

Additional resources

• Check out our EA-certified PoE designs here.
• Read the EA blog posts, “The Hazards of Passive PoE” and "Would you like a logo to go with your PoE system?"
• For more on the upcoming IEEE802.3bt standard, check out the TPS2373 and TPS2372 and read the blog post, “IEEE802.3bt: A Guide to Understanding the Current Spec.”

In this final installment of the topology blog series, I’ll introduce the inverting buck-boost converter and Ćuk converter. Both topologies allow you to generate a negative output voltage from a positive input voltage.

Inverting buck-boost converters

The inverting buck-boost topology can step up and step down its input voltage while the output voltage is negative. The energy transfers from the input to the output when switch Q1 is not conducting. Figure 1 shows the schematic of a nonsynchronous inverting buck-boost converter.

Figure 1: Schematic of a nonsynchronous inverting buck-boost converter

Equation 1 calculates the duty cycle in continuous conduction mode (CCM) as:

Equation 2 calculates the maximum metal-oxide semiconductor field-effect transistor (MOSFET) stress as:

Equation 3 gives the maximum diode stress as:

where V_in is the input voltage, V_out is the output voltage and V_f is the diode forward. The value for V_out needs to be negative for all three equations.

Since there is no inductor-capacitor (LC) filter pointing to the input or output of the inverting buck-boost converter, this topology has pulsed currents at both converter ends, leading to rather high voltage ripple. For electromagnetic interference (EMI) compliance, additional input filtering might be necessary. If the converter needs to supply a very sensitive load, a second-stage filter at the output might not provide enough damping of the output voltage ripple. In such cases I recommend using a Ćuk converter instead.

You can build an inverting buck-boost converter by using a buck controller or converter as you need a P-channel MOSFET or high-side MOSFET driver. However, the ground terminals of the controller or converter integrated circuit (IC) need to be connected to the negative output voltage. The IC is then regulating the ground signal versus the negative output voltage.

The right half-plane zero (RHPZ) is the limiting factor for the inverting buck-boost converter’s achievable regulation bandwidth. The maximum bandwidth is roughly one-fifth the RHPZ frequency. Equation 4 estimates the single RHPZ frequency of the inverting buck-boost converter’s transfer function:

where V_out is the output voltage, D is the duty cycle, I_out is the output current and L₁ is the inductance of inductor L1. The values for both V_out and I_out need to be negative.

Figures 2 through 7 show voltage and current waveforms in CCM for the FET Q1, inductor L1 and diode D1 in a nonsynchronous inverting buck-boost converter.

Ćuk converters

The Ćuk topology can step up and step down its input voltage while the output voltage is negative. The energy transfers from the input to the output when switch Q1 is not conducting. Figure 8 shows the schematic of a nonsynchronous Ćuk converter.

Figure 8: Schematic of a nonsynchronous Cuk converter

Equation 5 calculates the duty cycle in CCM as:

Equation 6 calculates the maximum MOSFET stress as:

Equation 7 gives the maximum diode stress as:

where V_in is the input voltage, V_out is the output voltage, V_f is the diode forward voltage and V_C1,ripple is the voltage ripple across the coupling capacitor C1. The value for V_out needs to be negative for these three equations.

The LC filter L2/Co in a Ćuk converter is pointing to the output. As a result, the output ripple is quite small, because the output current is continuous. When you look at the input, there is another LC filter with L1/Ci. Thus the input current is continuous as well, which results in very small input ripple, too. Thus the Ćuk converter is a perfect fit for applications that require a negative output voltage while being very sensitive at both the input and output, such as power supplies for telecommunications.

You can easily build a Ćuk converter by using a boost controller, because MOSFET Q1 needs to be driven on the low side. The boost converter or controller IC will typically only accept a positive feedback voltage at its feedback pin. You can translate the negative output voltage into a positive voltage signal by using a simple inverting operational amplifier circuit.

The Ćuk converter has an RHPZ as well. The power stage cannot immediately react to changes at the output, because the energy transfers to the output when switch Q1 is off. The maximum achievable crossover frequency is again one-fifth the RHPZ frequency. Note that a Ćuk converter has more than one RHPZ. Equation 8 estimates one of the Ćuk converter’s RHPZs as:

where D is the duty cycle, L₁ is the inductance of inductor L1 and C₁ is the capacitance of coupling capacitor C1.

Figures 9 through 18 show voltage and current waveforms in CCM for the FET Q1, inductor L1, coupling capacitor C1, diode D1 and inductor L2 in a nonsynchronous Ćuk converter.

Much like for a single-ended primary inductance converter (SEPIC) and Zeta converter, it can also make sense to use coupled inductors for a Ćuk converter instead of two separate inductors. Using coupled inductors offers two advantages: The first benefit is that only half the inductance compared to a two-inductor solution will be required for similar current ripple because coupling the windings leads to ripple cancellation. The second benefit is that you can get rid of resonance in the transfer function caused by the two inductors and the coupling capacitor. This resonance usually needs to be damped by a resistor-capacitor (RC) network in parallel with coupling capacitor C1.

One drawback to using coupled inductors is that you need to use the same inductance value for both inductors. Another limitation of coupled inductors is typically their current rating. For applications with high output currents, you might need to use single inductors.

You can also configure both inverting buck-boost and Ćuk converters as a converter with synchronous rectification if your application requires output currents greater than 3A. If you implement synchronous rectification for a Ćuk converter, you need to AC-couple the high-side gate-drive signal, because many controllers require you to connect them to the switch node. The Ćuk converter has two switch nodes, so take care to avoid negative voltage rating violations on the SW pin.

Additional resources

• Watch these TI training videos:
  • “Topology Tutorial: What is an Inverting Buck Boost?”
  • “Topology Tutorial: What is a Cuk converter?”
  • “Using a buck converter in an inverting buck-boost topology.”
• Design your power stage with Power Stage Designer.
• Download the “Power Topologies Handbook” and “Power Topologies Quick Reference Guide.”

Ethernet offers a more flexible networking technology for advanced driver assistance systems (ADAS), infotainment systems, body electronics and power trains; previous in-vehicle communication technologies required dedicated, special-purpose links and expensive cabling. The automotive amendments of the Institute for Electrical and Electronics Engineers (IEEE) 802.3 standard (100BASE-T1 and 1000BASE-T1) addressed electromagnetic interference (EMI)/electromagnetic compatibility (EMC) and enabled the use of unshielded single twisted pair cabling, which saves both cost and weight.

However, the 100 Mbps networks that have been widely used in ADAS, body electronics and power train do not provide enough bandwidth to connect all of these domains over a common backbone network that facilitates data fusion. Data fusion can enhance both the driver and passenger experience as well as create new opportunities to optimize vehicle performance and operation. With the advent of the 1000BASE-T1 standard supporting 1 Gigabit Ethernet (GbE), automotive network architects are now able to connect multiple 100 Mbps Ethernet domains and move data all over the vehicle. This need for a higher speed backbone is being driven by high resolution sensors (e.g., RADAR, LIDAR), the expansion of higher resolution video sources such as high definition (HD) cameras, HD video players, and HD resolution displays in front and back seats, and higher bandwidth telematics.

Connecting to 5G wireless networks under both mobile and static conditions will also force the migration from 100BASE-T1-based in-vehicle networks – which were sufficient to support 4G connections – to 1000BASE-T1 networks that can support links up to 1Gbps for 5G.

With the steady progression to gigabit streams, automotive processors and switches now support 1GbE+ Media Independent Interfaces (MII), which connect the Media Access Control (MAC) layer in the central processing unit (CPU), or switch, to network physical layer (PHY) transceivers. The 100Mbps versions of the MII (15-pin MII and nine-pin Reduced MII [RMII]) are complemented by 1Gbps versions, which include Reduced Gigabit MII (RGMII) and Serial Gigabit MII (SGMII). RGMII is a 12-pin interface, while SGMII can operate as either a four- or six-pin interface.

With a mixture of 100Mbps and 1GbE nodes, system designers prefer to develop common, reusable platforms that support both types of nodes. For example, connecting either a 1000BASE-T1 PHY or a 100BASE-T1 PHY to the same RGMII or SGMII port on a switch with little to no modification saves development time and cost and lowers system complexity, which improves reliability.

A 100BASE-T1 PHY that supports RGMII or SGMII offers an easy migration path to a 1000BASE-T1 PHY when needed. SGMII, using low voltage differential signaling (LVDS), offers the benefit of 10x the data bandwidth with fewer signal lines, shrinking solution size. RGMII still uses single-ended signaling, but again, offers a 10x increase in data bandwidth for only 3 additional signal lines, compared to RMII.

TI’s IEEE 802.3bw-compliant automotive Ethernet 100BASE-T1 PHY, the DP83TC811S-Q1, enables system designers to achieve the goal of systems that are more easily upgraded to 1 Gbps. It supports MII, RMII, RGMII and SGMII; all are selectable through either hardware bootstraps or register programming. The DP83TC811S-Q1 also makes RGMII and SGMII system verification and debugging faster and easier with its extensive diagnostic toolkit. The diagnostic toolkit supports several built-in-self-test (BIST) capabilities, such as a pseudo random bit sequence (PRBS) generator/checker and configurable loopback options. For example, the PHY is configurable for RGMII or SGMII loopback, allowing the connected MAC to send data to the PHY, which internally routes it to the receive data pins of the RGMII or SGMII port, enabling the MAC to verify continuity.

With its ability to support either RGMII or SGMII, the DP83TC811S-Q1 gives system designers the flexibility to implement 100 Mbps systems that can be easily upgraded to 1 Gbps when needed. The DP83TC811S-Q1 is fully supported by evaluation modules with user guides and graphical user interface, an input/output buffer information specification (IBIS) model and software drivers.

Additional resources

• Learn more about the importance of automotive Ethernet standards.
• Check out the evolution of automotive networking white paper.
• Explore TI’s automotive and industrial Ethernet PHY products 

Remember that game show “Are You Smarter than a 5th Grader?,” in which adult contestants attempted to answer questions from fifth-grade elementary school textbooks? The adults found these questions to be surprisingly challenging. Similarly, the “intelligence” being designed into modern-day appliances is similarly surprising and impressive. Vacuum cleaners, ovens and stovetops, washing machines, air conditioners, lawn mowers, and coffee makers are now evolving into touch-screen-enabled and remotely programmable devices with the ability to monitor and adapt to their environment – capturing surrounding data, making decisions and taking actions based on this data. The days when appliances were simply passive (or “dumb”) devices, used for human controlled and operated daily or weekly chores, are fast becoming a bygone memory.

Intelligent appliances

Robotic vacuum cleaners are one of the more visible examples of this evolution, as explored in our “Achieving increased functionality and efficiency in vacuum robots” white paper. These Wi-Fi®-enabled products are programmable on the device itself or remotely via a smartphone. Each new generation of robot vacuums incorporates better tools to increase both cleaning effectiveness (cleaning motors, dirt sensors) and room-mapping and object-circumnavigation efficiency (time-of-flight [ToF] sensors and cameras).

Smart ovens now include human machine interfaces (HMI) and video screens.  They also use both internal cameras and temperature probes, among other features. Internal cameras enable users to view the interior of an oven on a display or a smartphone. Employing a camera and video display instead of a see-through glass door increases heat conservation and efficiency. Further, using active temperature-probe monitoring, these ovens can be programmed to turn off and/or notify users when reaching a target temperature.

The latest connected washer and dryer appliances can monitor wash/dry cycles, informing users when clothes are clean or dry, providing usage statistics, and even notifying users when it’s time to order new detergent.

Refrigerators equipped with interior barcode readers connected via Wi-Fi to the internet can inventory their contents and notify users through an HMI display and/or smartphone of expired date codes.

Pod coffee makers enabled with cameras and bar-code readers enable the application of optimum temperature and water flow rate control, depending on the content of the pod (coffee, tea or cocoa).

As a final example, electric robot lawn mowers enable true hands-off yard maintenance, incorporating grass height and rain sensors to optimize operational efficiency. The random mowing pattern algorithms employed by these devices prevent the appearance of lawn mower tracks in the yard. And using sensors and automatically mowing the grass before it gets too high prevents thatch from forming.

TI technology for appliances

TI designs microcontrollers, microprocessors, sensors and connectivity devices to address the growing demands of designers and developers in the burgeoning smart appliance market.

TI’s Arm® Cortex®-based Sitara™ processor devices are configured with a variety of flexible peripherals, connectivity and unified software support to cover a wide set of intelligent appliance applications. Specifically, they are designed to interface with various motors, sensors and cameras, and then aggregate and process this data for decision-making and control. Related functions of the processor include HMI (touch-screen displays), graphics/video accelerators, voice command recognition and response using TI digital signal processors (DSPs) and Arm processors, and seamless wireless data communications via TI’s family of WiLink™ 8 devices.

From a software perspective, TI’s Processor software development kit (SDK), which provides a common user interface and software platform for all Sitara devices, enables users to leverage engineering resource investment across multiple Sitara Arm-based processor families.

TI also provides a wide variety of power-management solutions. For example, you could use either a power-management integrated circuit (PMIC) device or a low-cost discrete power solution design to power TI’s AM335x processor which features an Arm Cortex-A8 core.

TI’s broad portfolio of single- and multicore devices affords appliance designers an optimal balance of integrated connectivity and performance for the various demands of the intelligent appliance market. What additional features, functionality and intelligence would you like to see in your appliances?

Additional resources:

• Learn more about TI products in appliances. 
• Read  "Achieving increased functionality and efficiency in vacuum robots" white paper.
• Interested in appliances? Read "Cut the power and complexity of your appliance designs" blog post.