In the third installment of this series, I explored the importance of the clamping voltage of an electrostatic discharge (ESD) protection diode.

Although the main goal of an ESD diode is to protect a system during an ESD event, it has another equally important purpose to fulfill during normal operation: do absolutely nothing. While “doing nothing” may seem like an easy task, the presence of an ESD diode adds parasitic capacitance to the system. During an ESD event, the diode will break down and steer the damaging current to ground. When the diode is conducting, it can be modeled as an offset voltage V_BR (breakdown voltage) in series with a dynamic resistance (R_DYN). During normal operation, the diode is reverse-biased while data (or power) transmits through the trace. As a result, the diode’s depletion region stores electric charge, effectively becoming a capacitor with capacitance value C_L (Figure 1).

Figure 1: During an ESD event, the ESD diode breaks down at voltage V_BR and has a resistance of R_DYN (left); during normal operation, signals pass to the system and the ESD diode acts as a capacitor with capacitance value C_L (right)

If you don’t properly account for C_L, the diode will degrade the signal integrity of data passing through. For high-speed signals such as USB 3.0, USB 3.1 and High Definition Multimedia Interface (HDMI) 2.0, passing the eye-diagram mask test is required in order to achieve compliance with the interface standard. However, increased trace capacitance will increase signal rise and fall times and “shut” the eye. This could potentially push the entire system out of compliance (Figure 2).

Figure 2: A compliant USB 3.1 Gen 2 eye diagram (top); a noncompliant USB 3.1 Gen 2 eye diagram caused by high capacitance (bottom)

Designers usually have a capacitance budget to ensure that the entire system stays within compliance – there is no blanket maximum ESD capacitance requirement applicable to every design. For example, if the traces of system A are shorter than that of system B, system A will have more leftover capacitance to allocate toward ESD protection. Therefore, the ESD diodes of system A can have a higher capacitance and still be compliant to the standard. While the exact maximum ESD capacitance value will vary from system to system, Table 1 lists general capacitance and device recommendations for several popular high-speed interfaces.

A derating curve like the one shown in Figure 1 is an essential part of making a power module easy to use. With the derating curve, you can quickly see if the power module is rated to support your particular application’s requirements. In most cases, the derating curve shows the rated output current at various ambient temperatures. Operating below this line operates the power module within its temperature, power and/or current limits.

Figure 1 shows several derating curves for a MicroSiP power module, each for a different value of the junction-to-ambient thermal resistance, commonly known as Θ_JA. Wouldn’t you choose the power module that produces the green curve, since it has the lowest Θ_JA and the least derating?

Figure 1: Derating curve for the a MicroSiP power module

Actually, each curve in Figure 1 uses the same TPS82130 power module under the same operating conditions. Only the printed circuit board (PCB) layout and airflow have changed. You, the designer, choose which derating curve you get. This brings to light a key truth about power modules: their thermal performance, and thus their derating, is highly dependent on the application and usage of the device, which includes the PCB layout and system variables such as airflow.

Specifically, the red curve in Figure 1 is generated with the standard Joint Electronic Devices Engineering Council (JEDEC) PCB design. While JEDEC’s board definition is used to generate most thermal tables in device data sheets, the JEDEC board is not a very realistic type of board for final applications.

Figure 2 shows one difference, of many, between the JEDEC PCB and a more typical application PCB: the amount of copper connected to the device’s pins. The very small amount of copper (shown in purple) used in the JEDEC design yields unrealistically poor thermal performance.

Figure 2: The JEDEC PCB uses very thin amounts of copper connecting to the device’s pins

By focusing on the thermal design when using a power module, it’s possible to easily achieve better performance than the JEDEC PCB. Table 1 shows several design options using different numbers of vias, layers and airflow. All are an improvement over the JEDEC PCB design, quantified by the lower Θ_JA value and resulting lower operating temperature. Just through PCB and system design, you can reduce the operating temperature by nearly 50°C.

Table 1: Thermal-performance comparison of different PCB designs

Want to read more about this topic? Check out my article, “Improving the thermal performance of a MicroSiP power module,” in the Analog Design Journal.

A new engineering curriculum and kit based on robotics and hands-on lab exercises will help university students learn the fundamentals of analog and embedded-systems technology.

The TI Robotics System Learning Kit (TI-RSLK) is designed to inspire and prepare future generations of engineers by giving them a deep understanding of how electronic systems work and how to build comprehensive systems-level knowledge.

And it’s fun.

"I love watching kids jump up and down and shout like they’re at a championship game when their robots go around the track," said Jon Valvano, a University of Texas electrical and computer engineering professor who helped collaborate to develop the learning kit. "TI-RSLK is designed to energize, invigorate and motivate students. Along the way, they're learning the material deeply."

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Preparing tomorrow’s engineers

The TI-RSLK Maze Edition, the first in the series, is based on our SimpleLink™ MSP432P401R LaunchPad™ Development Kit and helps students learn the function and purpose of individual hardware components and how to integrate software. With that foundation, students can build their own functioning robot that can complete challenges and compete against other TI-RSLK robotic systems within a maze.

It comes with 20 learning modules. Each module includes lecture videos and lecture slides, lab exercises and demonstrative videos, downloadable code and sample projects, quizzes, and classroom activities. The kit and curriculum are fully customizable, which allows faculty members to choose how they integrate the modules into their classes. The kit can be used in a variety of engineering classes at any level along a student’s learning journey.

“With the TI-RSLK, students work in teams and use real-world engineering tools and design flows to solve problems – just as they would in the industry,” said Ayesha Mayhugh, a manager in our company’s University Program group. “Our hope is that all students feel equipped with a strong foundation in systems-level designs that sets them up well for future product designs.”

Through theory, practice and play, TI-RSLK prepares the engineers of tomorrow to thrive in a competitive professional landscape.

“Future engineers can’t push the boundaries of technology unless they first understand what the boundaries are,” said Peter Balyta, president of TI Education Technology and vice president of academic engagements and corporate citizenship. “I’m confident that as students gain a stronger understanding of how electronics systems work while in school, once in their career they will create the technologies of the future that will astound us all.”

Systems Learning From the Bottom Up

In her work, Ayesha has noticed that, despite the increase in hands-on projects, many students don’t understand the underlying principles and fundamentals of engineering. She has reached an important conclusion: "You can't hit the easy button for education."

TI-RLSK's curriculum solves for that gap in knowledge by enabling students first to understand the topic through step-by-step modules and then learn how it fits in a bigger system.

"I hope students figure out how to use this system in ways we never intended," Jon said. "I know I'm successful when students solve a more interesting problem than I ever anticipated."

Peter believes that the hands-on experience and theoretical knowledge provided by TI-RSLK will give students a great head start in their careers. "If they enter the workforce with an understanding of how the components of a product work together to create something useful, they'll be better engineers, better team members, better leaders and better innovators."

“Two roads diverged in a yellow wood, marked FemtoFET and SOT-23,

So I chose the path of FemtoFET to shrink my PCB”

 – Robert Frost (I think)

MOSFETs are being used as load switches more than they are being used in any other application, in volumes in the hundreds of millions at a time. I should probably start with exactly how I am defining “load switch” here. For the sake of this post, consider a load switch any small-signal FET whose only function in a system is to pass along (or block) some low-current (<1A) signal to another board component. Battery-protection MOSFETs have very similar functionality, but represent a unique subset of load-switch applications that can also carry much higher currents.

Our applications team has a word for load switch FETs – “pixie dust” – to describe the somewhat ubiquitous way that they can be “sprinkled” over a system after most of the design is complete. That perhaps does these tiny powerhouses a disservice, in that they are also often the glue that holds the electronic system together.

The small signals that these devices carry are generally on the order of a few hundred milliamps such that in theory, there is no reason that the function can’t be integrated. However, custom integrated circuits (ICs) are often more costly than they are worth, such that once a design is complete, it is easier to implement a few of these small signal FETs rather than requesting or redesigning a custom IC. Given that, there are typically two fundamental requirements for these devices: that they be cheap and small. Which of these requirements is the most critical will dictate what type of MOSFET is most appropriate for your design.

If cost is the most important factor, small-form-factor packages like the small-outline transistor (SOT) series (SOT-23, SOT-26, SOT-323, SOT-523) will be the most preferable option. These devices have a PCB footprint from 2.6mm² to 10mm², on-resistances in the range of several hundred milliohms to a few ohms, and can handle currents up to roughly half an amp (depending on the resistance). They are comprised of large protruding leads and a somewhat bulky package (see Figure 1). While some industrial designers prefer the external leads, as they make for simple board mounting and enable easy visual inspection for a solder connection, the strongest appeal of these FETs is their low cost (think a penny or less). I should note that TI really doesn’t have any offerings for MOSFETs in these packages, or intention to play in this commoditized space. 

Figure 1: Several SOT packages (not drawn to scale)

On the other hand, if reducing the PCB space taken up by many extraneous small-signal transistors is the biggest concern, a better solution is either a bare-die chip-scale package (CSP) or land grid array (LGA) device. TI carries a wide variety of these types of devices, the most popular being from our FemtoFET product line (Figure 2). These devices have an ultra-small footprint, offering size options all the way down to just under 0.5mm². This tiny form factor inevitably means high junction-to-ambient thermal impedance through the PCB. However, with resistances that can be one to two orders of magnitude less than the larger-footprint SOIC package devices, the reduced conduction losses more than make up for the slight increase in thermal impedance, enabling higher current-handling capability in some cases greater than 1A.

Figure 2: Three different FemtoFET package offerings (not drawn to scale)

Before selecting which of the above roads to travel down, I offer two final caveats. The first is that before committing to a FemtoFET (or some other ultra-small device), you should check your PCB manufacturing capabilities. Some industrial manufacturing processes prefer a larger pitch between mounting pads (hence the preference for SOT devices). Others can handle pitches down to 0.5mm (like the F5 FemtoFET family), while personal electronics manufacturers can often handle pitches down to 0.35mm (supported by the F4 and F3 FemtoFET packages).

I’ve spoken at length about current ratings before, but because the sole purpose of a load switch is to carry small currents, it’s worth revisiting one more time. As usual, the best practice is to ignore the front-page current ratings, and instead work backwards from how much power loss you think your system will permit the FET to dissipate.

Most data sheets will provide a junction-to-ambient thermal impedance (R_θJA) for a minimum and maximum copper (Cu) PCB scenario. Using the minimum Cu as a worst case is the safest bet, although if you know the end board dimensions, you could try to interpolate an R_θJA between the minimum and maximum Cu impedances provided on the data sheet. Then, using Equation 1 below, and knowledge of the end equipment’s worse-case ambient environment, you can calculate how much power the FET can handle, and therefore current as well:

One nice thing about load-switch applications is that the device is either on or off. Therefore – unlike all the other applications I’ve discussed to this point in this series – all of the power losses are due to conduction losses (I²R).

Thanks for reading. In the next post, I’ll take a more in-depth look at a subset application of load switches that I mentioned at the beginning: FETs used for battery protection.

Additional resources

• For more information about FemtoFET devices, check out Kevin O’Connell’s blog post, “FemtoFET MOSFETs: small as sand but it’s all about that pitch.”
• Although Kevin touches on it in his post, for a more thorough explanation of how to mount these tiny devices, read the “FemtoFET Surface Mount Guide.”
• Finally, in the blog post, “Shrink your industrial footprint with new 60V FemtoFETs,” I discussed the first 60V FemtoFET industrial load switch, the CSD18541F5.

Electrical grid systems are always trying to mitigate the risk of overcurrent events that can disrupt the flow of power from a power-generation source to millions of homes and businesses. To measure currents and voltages accurately, energy providers use equipment to monitor different parts of the power grid.

One of the most critical pieces of grid equipment is the protection relay. A relay can monitor several current transformers and potential transformers at the same time. When the relay detects unusual behavior, it activates a circuit breaker to prevent damage to the grid network. A protection relay system typically includes subsystems for measuring current or voltage, communicating information back to a substation control room and displaying information on the actual relay device.

Older relay devices relied heavily on analog circuitry to detect overcurrent events, but modern digital processors are capable of detecting events quickly and accurately, and can use up less space. One way to implement a current-measuring subsystem is by using the programmable real-time unit-industrial communication subsystem (PRU-ICSS) in TI Arm®-based Sitara™ processors, as shown in Figure 1.

Figure 1: Overview of Sitara processor with Arm cores

The PRU-ICSS subsystem consists of two 32-bit reduced instruction set computer (RISC) cores designed for real-time processing, and enables additional general-purpose inputs and outputs. As an example, TI created the Flexible Interface (PRU-ICSS) Reference Design for Simultaneous, Coherent DAQ Using Multiple ADCs, which uses the PRU-ICSS to measure the output of six 8-channel ADS8688 analog-to-digital converters (ADCs) with a BeagleBone Black. Data from the ADCs are fed into the PRU-ICSS through general-purpose input pins; each PRU core then performs additional filtering functions, as shown in Figure 2.

Figure 2: PRU-ICSS processing of ADC data

Using a PRU-ICSS has several advantages over a dedicated hardware Serial Peripheral Interface (SPI) peripheral. First, you can reconfigure the PRU-ICSS pins to connect to a variety of devices, whereas an SPI interface cannot. Second, the PRU-ICSS can run independently of the host processor to reduce processor loading where an SPI interface will send interrupt commands to the processor. Processing the data with a dedicated PRU-ICSS subsystem also enables faster ADC sampling speeds, since there are no longer competing actions for the host processor. Third, the PRU-ICSS can compensate for delayed clock edges, whereas SPI peripherals require tight control over timing requirements.

The AM335x processor family used in the reference design is limited to only one PRU-ICSS, but a processor family like AM57x devices has two. Now it becomes possible to have an analog monitoring subsystem, a communications subsystem for redundancy protocols and a human machine interface (HMI) like that shown in Figure 3.

Figure 3: Example of a protection relay based on the AM57xx processor

The Sitara portfolio includes a wide range of devices for hardware scalability, but also enables software reuse with the Processor SDK for a common development framework. This flexible hardware and software platform can enable customers to design a wide range of protection relays for a smarter grid infrastructure.

Additional resources

• Download these reference designs:
  • “Human Machine Interface (HMI) for Protection Relay Reference Design.”
  • “High-Availability Seamless Redundancy Ethernet Reference Design for Substation Automation for Linux.”
  • “Parallel Redundancy Protocol Ethernet Reference Design for Substation Automation on Linux.”
• Learn more about Sitara processors for grid infrastructure.

As our world becomes increasingly reliant on technology, global energy consumption is growing dramatically. Driven by many applications – including data centers, automotive and industrial – global consumer spending on electricity has neared spending on oil products.⁽¹⁾ To support these trends, designers are utilizing semiconductor solutions, leading to the worldwide purchase of 824 billion semiconductors in 2016 to power their homes, cars and workplaces.⁽²⁾

Designers of these products seek power-management technologies that enable them to work more competitively while complying with environmentally conscious energy-usage laws.

Two years ago, we described three key power and energy management trends that would dominate our industry through 2020. The trends we identified – energy efficiency, power density, and big-data storage and delivery – are growing and are still among the top key challenges in 2018. With the speed of technological evolution, three additional trends drive our work today: distributed and renewable energy, electrification of vehicles, and the automation of factories and industrial buildings.

We provide power-management technologies to design engineers across many applications, and our innovations address the toughest power-management challenges in all six of these categories. Here's why we've zeroed in on these six trends – and how we're addressing them:

1. Energy efficiency

By 2020, data centers are expected to consume more than 73 billion kilowatt hours of electricity per year – enough to power more than 10 million average homes.⁽³⁾ The more data they churn, the more energy data centers require for cooling and the greater burden they place on the grid.

According to the U.S. Department of Energy, adopting additional energy-efficiency strategies could result in a 45 percent reduction
in electricity demand.⁽⁴⁾ We can reduce energy demands from data centers with new strategies and technologies that minimize loss and improve efficiency.

Improving energy efficiency delivers savings in two areas – reducing the energy required in data-center transactions and reducing the overall cooling requirements for servers. Innovation opportunities exist all the way up to the server power-delivery architecture and all the way down to point-of-load topologies.

New topologies – such as resonant and hybrid DC/DC converters – offer the benefit of reduced size, improved efficiency and lower temperature rises. Combining these techniques with algorithms allowing for low idle power consumption and fast wake takes us a significant step toward the 45 percent reduction predicted by the U.S. Department of Energy.

At the macro level, server systems are limited by the number of power-conversion steps. By investing in topologies that allow for direct conversion, new power delivery schemes previously deemed impractical are now within reach. Imagine eliminating three conversion steps by going from 400-volt DC distribution directly to the CPUs. These types of disruptive approaches are enabled by innovations in power management and semiconductors. 

2. Storing and delivering big data

As global demand for rapidly accessible data continues to grow, so too will the demand for energy to store and retrieve data. Controlling the costs and environmental impact of that demand will be a critical challenge.

Cloud storage has exploded over the last few years with consumers uploading and storing more information on the cloud than ever before. Each of these transactions uses energy. For example, the process of recording a home video, uploading and storing it to the cloud, and retrieving it later requires energy. By enabling power-management solutions with the highest active mode efficiency, low sleep power consumption and ultra-fast wake-up times, semiconductors can enable all of these transactions at the minimum required energy consumption. 

3. Power density

Despite improvements, power density of power supplies has not scaled with Moore's Law. As semiconductors enable more features, power demands increase. For example, the rapid adoption of mobile phones across the planet was, in many ways, enabled by lithium ion battery technologies that allow more features in the phone while maintaining sufficient battery life for the phone to last a day.

What can be lost in that trend is that as batteries get bigger and better, the chargers that supply them have lagged behind. One could imagine a scenario where a full-featured smartphone might last all day but it might then take all night to charge. Improved power density is the key to enabling better user experiences.

Our company has invested heavily in power density. One of those investments, directed toward the battery charger will debut at the APEC 2018 conference – so stay tuned.

4. Distributed and renewable energy

There's a clear demand to generate and distribute energy more efficiently. The challenge lies in enabling power conversion and processing of different energy sources with maximum efficiency. Gallium nitride (GaN) and Silicon Carbide (SiC) offer this potential by combining the unique ability to operate at high voltages with high efficiency and small size.

Although limited in their adoption until now, both GaN and SiC demonstrate previously unattainable efficiencies and densities at voltage ranges necessary to support distributed and renewable energy.

To take these technologies from interesting prototypes to mass adoption, we believe that integration of the gate driver in the package can make the difference. In the LMG3410, we have demonstrated that having the gate driver in close proximity to the devices enables the necessary performance and manufacturability to take these technologies to the next level of adoption.

5. Electrification of vehicles

It’s easy to see how cars have changed over the last 10 years. The number of electronics in each new generation of cars continues to accelerate. Features such as automatic braking, lane-departure sensors and automatic-beam steering headlights are now commonplace and enabled by semiconductors and power management. Even the number of electric vehicles – previously limited in adoption due to range, cost and charge time – are expected to expand from 2 million to 280 million by 2040⁽⁵⁾ due largely to improvements in semiconductor-based electronics.

Inside the car, integrating more electronics provides consumers with better experiences, but with these technology improvements comes the challenge of electromagnetic interference (EMI). EMI, both radiated and conducted, can create interference in mission-critical systems, leading to a disappointing user experience or, worse, safety concerns.  

EMI mitigation has therefore become a huge challenge and a huge innovation opportunity. Investing in techniques ranging from spread spectrum (see TPS55165 for example) to adaptive gate drivers to active noise cancellation enables even faster acceleration of electronics and technology in future vehicles.

6. Industrial automation

Industrial automation offers the ability improve productivity and manufacturing efficiency. With this opportunity comes the challenge of safety. Automated factories often have heavy equipment requiring high voltages to operate, making them harsh and potentially dangerous.

A key enabler for industrial automation therefore becomes isolation technologies that allow for sensor nodes and operators to work effectively and safely in the presence of high voltages. Imagine having the ability to transfer lower power to various sensor systems while protecting the operator from voltage surges 60 times greater than household voltages across a distance less than the diameter of a coin. These are exactly the technologies we enable when designers use devices such as the ISOW7841.

Our company is addressing the opportunities and challenges these trends present by developing new technology. We’re excited that our innovations are helping customers solve their power and energy-management challenges.

Jeff Morroni is director of power management for Kilby Labs, our company’s research-and-development group. He holds a doctorate in power management from the University of Colorado, Boulder.

1. IEA.org

2. WSTS

3. Department of Energy Also see: http://www.datacenterknowledge.com/archives/2016/06/27/heres-how-much-energy-all-us-data-centers-consume

4. Department of Energy

5. IEA.org

6. Nanochip Fab Solutions 

CHMSL stands for the center high-mounted stop lamp. In a vehicle, the CHMSL is mounted above the left and right brake lights (also called stop lamps).  According to the National Highway Traffic Safety Administration, when brakes are applied, the CHMSL provides a conspicuous and unambiguous message to drivers of the following vehicles that they must slow down. Since the CHMSL is mounted in addition to the left and right brake lights, it is also known as the “third brake light.” Some vehicles, such as pickup trucks, feature a reverse light integrated in the CHMSL in addition to the brake light function.

A CHMSL implementation using discrete components

In modern vehicles, the illuminant inside the CHSMSL is mostly based on light-emitting diode (LED) strings. Transistor-based circuits drive the LED strings in the CHMSL. CHMSL LED driver circuits are typically linearcircuits as opposed to switchingcircuits; that is, the LEDs are driven with circuits in which the transistor operates in its linear region.

Designers often realize the LED driver circuit in a CHMSL with discrete components, using separate resistors and low-side bipolar junction transistors (BJTs) or circuits. Figure 1 shows an example of a discrete LED driver circuit for a CHMSL. In this circuit, the CHMSL consists of two LED strings where each string is based on two red LEDs in series. The BJTs are on the lower side of the LEDs.

Thermal considerations

You must consider thermal performance when designing linear LED driver circuits. The circuit design and component choices have to ensure the components are not getting hot to the point of damage. Based on the schematic in Figure 1, you can see as the supply voltage increases, so does the voltage across the BJT and the resistor, thereby increasing power dissipation in these components. More power dissipation implies higher temperatures. Thus, in linear LED driver applications, the input voltage range contributes to most of the thermal concerns.

To analyze thermal issues for the schematic in Figure 1, consider an example in which the total CHMSL LED current is 90mA, so each LED string is driven with 45mA of current. With a 16V supply voltage, Equation 1 calculates the maximum voltage drop on the BJT to 9V:

Equation 2 calculates the maximum power dissipation of the BJTs to 0.81W:

Assuming the maximum operating ambient temperature is 85°C, and by using BJTs in the small-outline transistor (SOT)-223 package with a thermal resistance of 80°C/W, Equation 3 calculates the maximum BJT junction temperature as:

This calculation shows the junction temperature is very close to the typical maximum allowable junction temperature of 150°C.

In order to improve the circuit’s thermal performance, using two transistors in parallel splits the power dissipation, enabling the maximum temperature to stay below 150°C even in worst-case conditions, as shown by the calculation in Equation 4:

When using a different BJT package type with a higher thermal resistance, you need more BJTs to split the power dissipation. The number and size of transistors in parallel is mainly based on the LED current and the maximum power dissipation allowed in the transistors.

A CHMSL implementation using integrated LED driver ICs

Another way to drive the LEDs is to use a specific linear LED driver integrated circuit (IC) such as TI’s TPS92610-Q1, as shown in Figure 2. In such driver ICs, the transistor and transistor driver circuit are all integrated in the IC. The transistor is still operating in its linear region. Because all of the components are integrated inside the IC, you only need the IC and one sense resistor for this solution.

Figure 2: TPS92610-Q1 integrated LED driver circuit

Thermal considerations again

Let’s look at thermals in this design; specifically, the junction temperature of the IC. With a 16V supply voltage, Equation 5 calculates the maximum voltage drop on the IC as 11V:

Assuming the same 90mA of current, a maximum voltage drop of 11V on the IC and a thermal resistance of 52°C/W, Equation 6 calculates the maximum junction temperature:

136.5°C is well below the maximum specified IC junction temperature of 150°C. Thus, you need only one driver IC to operate the example CHMSL LED strings.

Advantages of an integrated solution

One obvious advantage of an integrated solution over a discrete solution is the reduced number of components. Reducing the number of components on the board obviously leads to lower space requirements.

Another key advantage is the current regulation accuracy over the full temperature range. The driver IC can maintain constant current in the IC as the forward voltage of the LEDs change with temperature. This is in contrast to the discrete circuit shown in Figure 1, which cannot regulate current in the LED as the temperature changes.

The third advantage of a linear LED driver IC-based solution is its diagnostic features, which enable the detection of LED circuit faults such as LED opens and shorts, and notify the driver of faults.

Finally, the implementation shown in Figure 2 could be cheaper than the implementation in Figure 1 when considering the number of components and the cost of each component.

More information

The Automotive Linear LED Driver Reference Design for Center High-Mounted Stop Lamp (CHMSL) is an integrated solution for driving LED strings for a CHMSL, which includes brake and reverse lights. Each light is capable of independent control by applying power to its supply line. The design uses three TPS92610-Q1 automotive-qualified linear LED drivers, which result in a low bill-of-materials count and feature-rich solutions.

For other interesting automotive body electronics and lighting solutions, check out TI’s Body Electronics and Lighting overview page.

Join Texas Instruments at the Applied Power Electronics Conference (APEC), March 4-8, in San Antonio, Texas to experience the latest innovation in key applications, interactive design stations and advice from our experts.

If you’re not attending in person, follow this blog for real-time updates and monitor us on social media for the latest:

• Facebook
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Visit our booth #501 to see new products and end-to-end power-management system solutions including hardware, software and reference designs that give designers the power to:

Innovate:

• The Industry’s Fastest and Most Efficient CrM Totem-Pole PFC Design: This critical conduction-mode reference design features TI’s 600V GaN power-stage technology and Piccolo™ F280049 controller to achieve up to 99% efficiency at full load. The 1MHz, high-density-interleaved 1.6kW design is ideal for space-constrained applications such as server, telecom and industrial power supplies. Interleaving the power stages reduces input and output ripple currents. The hardware of this device is designed to pass conducted emissions and surge requirements, helping designers achieve 80 Plus Titanium specifications. Download the TIDA-00961 reference design.

Design:

• Get to market faster – WEBENCH^® Power Supply Design tool: Analyze and interpret designs with WEBENCH Power Design tools. Go beyond the traditional concerns of performance, footprint and cost with tools that mitigate electromagnetic interference (EMI) noise and handle noise-sensitive loads. Start a design now at TI.com/WEBENCH.
• Work smarter, not harder - Power Stage Designer ™ tool: Power Stage Designer™ is a JAVA based tool that helps engineers accelerate their power-supply designs by calculating voltages and currents of 20 topologies according to the user’s inputs. Additionally, Power Stage Designer contains a Bode plotting tool and a toolbox with various functions to make power supply design easier. Because all calculations are executed in real time, this is the quickest tool to start a new power supply design. 

Learn:

• Join TI at technical sessions: Join TI power experts at more than 30 technical sessions covering topics such as renewable energy systems, wireless technology and GaN device reliability validation. 
• Power up: 6 power management trends to address growing energy requirements: Circuit designers are seeking innovative technologies to address power-management challenges presented by fast-growing global energy consumption. Read the blog to see the 6 trends addressing some of their toughest requirements.
• Power waveforms and equations and more, oh my!: Download the Power Topologies Handbook for waveforms and equations of the most common hard switched power supply topologies and the soft switched Phase-Shifted Full-Bridge.
• Get a TI Power Management Lab Kit: Check out the TI Power Management Lab Kit (TI-PMLK) buck-boost board and experiment book to better understand the trade-offs related to common power-supply parameters such as power losses, converter efficiency, stability, load and line regulation, and more.

(Please visit the site to view this video)
Matthew Miao understands firsthand the power of engineering to transform lives, and he and other TIers are using that power to help students in China think about their future in exciting new ways.

“We want to open the eyes of kids today to the possibilities of what they can be when they engineer their future,” he said.

As a young man, Matthew assumed he would follow in his father’s footsteps and spend his life mining coal in northern China. Then one day, volunteers from a local university visited his middle school and gave his class a basic overview of engineering. With that visit, the arc of his life transformed from ambivalence into an eagerness to learn.

“Those volunteers set a life-changing example of what it’s like to be an engineer,” said Matthew, an audio algorithm validation engineer who lives and works in Shanghai.

Matthew and other members of TI’s Community Involvement Team (CIT) in China are telling their stories to children and students at TI Project Hope Schools, which include donations of about 370 multimedia classrooms provided by our company. Together with local partners, we are working in China and other places around the world to ensure that students in communities where we live and work are prepared for the future.

“I’m so excited that I’m doing the same thing with TI that the volunteers did when they visited my middle school many years ago,” Matthew said. “Children are always the main emphasis of our China CIT. It can’t be better than bringing laughter and hope to these kids, especially children with disabilities.”

Project Hope Schools

Except for the dusty dirt roads and simple brick buildings outside its gates, one would never know that the Project Hope School in Dongnan Town is located in one of the poorer areas of China’s Shaanxi Province. The school is freshly painted bright yellow, with blue and white accents, and has an expansive playground for its 230 students.

The school is the fourth of what will be 10 planned Project Hope Schools that our company has funded in China. We’ve joined with the China Youth Development Foundation, a national public foundation with the Ministry of Civil Affairs, to bring these schools to impoverished rural areas of China.

“We’ve chosen to partner with the China Youth Development Foundation on Project Hope schools to make education accessible to all students in China, especially its rural areas,” said Andy Smith, our company’s director of Corporate Philanthropy. “Education matters and we want to ensure that all students have the opportunity to learn, grow and contribute by having access to an environment where they can explore math, science, reading and writing.”

To date, 3,100 teachers and 48,500 students from Sichuan, Jiangxi and Shaanxi provinces are benefitting from our giving and employee engagement efforts that help Chinese students learn about engineering concepts and, in turn, help strengthen our communities.

In addition to teaching kids about electronics, Matthew and other members of the China CIT work with autistic children in Shanghai.

“If you’re patient with them, they’ll feel the love from you,” Matthew said. “One parent of a disabled child told me that his daughter has never been so happy as during the past month when we worked with her. That inspired me to join more volunteer activities with the CIT team.”

All in a day’s work

For the China CIT, volunteerism is all in a day’s work.

In 2017, more than 1,000 employees in China invested 4,500 hours volunteering at schools in their local communities, working with disabled children and planting trees. They also participated in charity races to raise money for 60 multimedia classrooms in Project Hope Schools. Each multimedia classroom includes projectors based on TI DLP® technology, computers, white boards and software.

Bringing technology to life

For Steven Zhou, however, equipping classrooms with multimedia equipment wasn’t enough to narrow the digital gap for students in China’s rural areas. He thought something more was needed to bring the power of technology to life for students as part of their regular coursework.

Steven, who is a salesperson in our company’s Shanghai office, decided to develop a course to teach students about the basics of the integrated circuit in a fun, interactive way. He has taught the course to more than 1,000 students.

“The Magic Electronics Course helps young children easily understand the concepts of an integrated circuit and new technology in a hands-on way,” Steven said. “Our purpose is not to teach them too much about semiconductors, but instead to help them see the important role that ICs play in modern life. We show them real-life examples that they can recognize, which is especially important for children who live far away from big cities.”

Modern factories feature automated systems that rely on feedback from many sensors across the factory floor to maintain high productivity. These factories use a digital fieldbus to aggregate the enormous amount of data that the sensors collect. The more data that the sensors gather, the better the system can adapt and operate.

As a result, modern fieldbus-connected industrial sensors must detect signals at a faster and more precise rate and output that information as a digital signal versus a conventional analog signal. This functionality requires more powerful processors for the sensors. Plus, because there are more of these sensors in the factory, the form factor is shrinking. The increased power requirements and shrinking form factor are forcing a change from the proven linear regulator solution to a switching regulator solution.

Using a switching regulator poses new challenges. A switching regulator will have a larger form factor because of the additional area that the inductor requires. You must consider the regulator’s switching frequency in relation to the frequency of the measurement signal.

The layout of the switcher is more critical. A poorly designed switching regulator will raise the noise floor and generate unwanted electromagnetic compatibility (EMC) that will interfere with the detection of small signals.

Fortunately, there are now integrated inductor DC/DC switching regulators available that minimize many of these challenges. Integrating the inductor reduces the switch-node area and makes an optimal layout much easier. The switching frequency of new DC/DC converters has increased significantly, enabling the use of small-chip inductors and ceramic capacitors to make the DC/DC switcher the smallest option.

The new LMZM23601 power module integrates a DC/DC converter, inductor, Vcc filter capacitor and boot capacitor in a 3mm-by-3.8 mm-by-1.6mm package. It can handle input voltages up to 36V and steps down to voltages from 15V to 2.5V (with fixed 5V and 3.3V options) while delivering up to 1A of output current. As you can see in Figure 1, you can realize a complete 1A solution in a minimal amount of board space.

Figure 1: The LMZM23601 solution for 3.3V or 5V outputs at up to 1A

Let’s take a look at how the LMZM23601 compares to the traditional linear regulator options for a field transmitter application with these requirements:

• Input voltage: 10V to 30V, 24V nominal.
• Output voltage: 3.3V.
• Output current: 35mA.
• Temperature range: -40°C to 85°C ambient.
• Board area: 40mm by 4.5mm.

As Table 1 shows, the LMZM23601 is at an advantage in terms of package area and thermals compared to a linear regulator in a mini small-outline package (MSOP)-8. Note that the R_ӨJA specified in Table 1 is only a reference for comparison, since it will be much higher in an actual sensor application given the limited amount of board space and copper. A Joint Electron Device Engineering Council (JEDEC) or an evaluation module (EVM) calculates the typical R_ӨJA value found in the data sheet. As an example, the LMZM23601 R_ӨJA of 45°C/W is based on a 30mm-by-30mm two-layer board.

Table 1: LMZM23601 vs linear regulator design options by package type 

Looking at Table 2, the linear regulator is dissipating (24V-3.3V) x 35mA = ~0.93W of power, while the LMZM23601 is dissipating only 0.116W. The temperature rise in the MSOP-8 package linear regulator results in a junction temperature above the standard integrated circuit (IC) junction temperature of 125°C, while the junction temperature for the LMZM23601 is 90°C based on a 45°C/W R_ӨJA. Even multiplying the R_ӨJA by a factor of five would still yield a Tj max below the junction temperature.

From this example, it is clear that a linear regulator is not a viable option in terms of thermals. The trade-off of going with a switching solution (even a module such as the LMZM23601) is that you now must consider the output ripple. As shown in Figure 2, the output ripple from a standard LMZM23601 design for a 3.3V output is about 3mV peak to peak.Table 2: Thermal considerations for a 24V-to-3.3V conversion at 35mA

Figure 2: Output ripple from the LMZM23601EVM for a 3.3V output

To further reduce the output ripple, you can use a second-stage filter like the one shown in Figure 3. Figure 4 shows that the output ripple has been reduced from 3mV peak to peak to <1mV peak to peak.

Figure 3: The LMZM23601 with a second-stage filter

Figure 4: LMZM23601 output-voltage ripple with a second-stage filter

For industrial sensors with tight board space requirements, a switching regulator is the only viable option. The LMZM23601 integrated inductor delivers high performance in a solution size smaller than a linear regulator, but with the efficiency of a switching regulator.

Additional resources

• Read the blog: “Design a second-stage filter for sensitive applications.”
• Download the application report, “Semiconductor and IC Package Thermal Metrics.”

Since its introduction many years ago, millimeter wave (mmWave) radar has come a long way, with designers now interested in its use for applications such as traffic monitoring, semi-autonomous vehicles and factory automation. The three key measurements that make mmWave radar valuable in applications like these are range, velocity and angle.

In this second installment of a four-part series, I’ll dive deeper into range measurements and how they impact a radar’s usefulness in a variety of applications. In my last blog post, I said, “there is more to measuring range than simply the accuracy of the measurement. Range resolution is the ability to distinguish between two closely spaced objects …High-range resolution also helps improve the minimum measurable distance, which means that the system can detect objects closer to it.”

Here are three videos that show the importance of range measurements in a variety of different applications:

(Please visit the site to view this video)

This experiment was designed to determine the farthest distance at which mmWave technology could still detect an object as small as a coin. We were able to determine that the technology could distinguish a quarter at 2m. While the automotive applications are obvious – being able to see objects or debris in or near the road, as well as pedestrians, cyclists and other cars – you can also imagine how the ability to distinguish small objects would be useful in industrial settings.

Imagine a warehouse staffed by a mixture of robots and humans, which move around the warehouse selecting, packaging and shipping items purchased by customers. If an item is dropped in the path of a robot, an mmWave sensor must be able to detect that object, determine the range or how far away it is, and determine how to get around that object.

(Please visit the site to view this video) 

Imagine that the mmWave radar sensor depicted in this video is fixed to a traffic light or street lamp. By detecting the distance as well as the number of objects in the path of the radar beam, as well as whether those objects are moving, the traffic light could decide to turn green or red at precisely the correct moment to keep traffic flowing smoothly. Or a street lamp could illuminate just before a passing driver or pedestrian needs light and shut off shortly after, reducing electricity costs.

(Please visit the site to view this video) 

TI’s mmWave sensors can take advantage of their small wavelengths to measure very minute changes in range. As this video illustrates, such capability means that mmWave technology can detect vital signs, such as breathing or heart rate. You can imagine a number of different applications for this, including detecting a child or pet left behind in a hot car. Or a semi-autonomous car could navigate off the road in the event that the driver experiences a dangerous health condition, such as a heart attack, stroke or seizure.

As you can see, range is a valuable measurement that enables mmWave radar sensors to detect and understand their environment, both in automotive and industrial settings. Velocity and angle are additional measurements that, when combined with range, produce additional details about an environment, which I’ll discuss in the next installments of this series. In the meantime, check out the “The fundamentals of millimeter wave sensors” white paper for more information on how mmWave sensors use these measurements to see and understand their environment.

In a previous blog post, my colleague Gavin Bakshi discussed the highway addressable remote transducer (HART) protocol and its place in sensor transmitter designs. To recap, simple transmitter designs traditionally communicate an analog value, typically referred to as the process variable (PV), through a current loop. This PV is generally tied to a sensor value (humidity, temperature, pH, pressure) that is represented by a 4-to-20mA analog signal. The analog value can traverse kilometers of wire in reaching the analog front-end circuitry, which records the potential drop across a shunt resistor in interpreting the transmitted sensor value.

Now, this is great if you want to communicate one value over lengthy cabling. But what do you do if you want to send or receive additional data over the same two wires? By putting HART into your transmitter design.

By including a HART modem, your transmitter design can now communicate extensive calibration routines, send diagnostic data or communicate PVs from other included sensor platforms. This communication is possible through the HART frequency shift-keying (FSK) waveform, which couples onto the analog current signal.

Before diving into the nitty-gritty of two-wire HART transmitter design, take this crash course (or refresher) on a simple two-wire transmitter design. Did you finish the review? Awesome! You’re halfway there.

Let’s start off with the circuit shown in Figure 1.

Figure 1: Two-wire transmitter with HART modem

I know that the circuit may look a little daunting, but the only difference between this circuit and the one shown in the simple two-wire transmitter design blog post is the inclusion of the DAC8740H HART modem. The low quiescent current of the DAC8740H HART modem, 180µA, makes the modem an excellent candidate for low-power sensor transmitter solutions. Using the methods shown in the crash course will determine a gain of (1 + R3/R4) for the loop current.

There are only two connections between the HART modem and transmitter shown in Figure 2. The DAC8740H MODOUT pin of the HART modem connects to the transmitter through an AC-coupled capacitor, C1. This capacitor, along with R6, creates a high-pass filter that attenuates frequencies lower than the chosen cutoff frequency, 1/(2 × π × R6 × C1).

Figure 2: Superposition of HART modem

During operation, the HART FSK signal is driven from MODOUT and superimposed onto the loop current analog value with an FSK amplitude of 1mApp. Resistor R6 can change and set this FSK amplitude, which is connected in series from the HART modem to the noninverting terminal of U3. Though superposition, Equation 1 calculates the AC component of the current loop as:

 IOUT p-p = (VHART/R6) (1 + R3/R4)                           (1)

Therefore, R6 = (VHART/IOUT p-p) (1 + R3/R4).

Substituting schematic values for R3, R4 and the peak-to-peak voltage of MODOUT will reveal the value of R6. Once you have the value of R6, you can calculate C1 by choosing the cutoff frequency of the high-pass filter. In the Highly Accurate, Loop-Powered, 4mA to 20mA Field Transmitter with HART Modem Reference Design, the cutoff frequency is 679Hz, ensuring that noise and frequencies lower than 1,200Hz and 2,200Hz are effectively attenuated without significantly impacting the HART band frequency range.

The HART signal receiving pin – the DAC8740H MOD_IN pin – connects to the positive bus supply net of the transmitter circuit through an AC-coupled capacitor, C2, and into an internal bandpass filter.

You’ve done it! You’ve now completed a transmitter design with plenty of HART to go around! The next step is to create an intelligent sensor transmitter solution by selecting a sensor interface, like the TMP116, which provides better accuracy than a Class A resistance temperature detector (RTD) all from a single chip.

Additional resources

• Download the DAC8740H data sheet.
• View the DAC8740H product folder.
• View the TMP116 product folder.
• Check out TI’s system monitoring and protection sensing devices to complete your sensor transmitter.

Although the automotive instrument cluster has evolved in the last few years, it has in many ways remained the same information center with which your grandparents would be familiar. Consider its origins as a panel with analog (mechanical) gauges showing vehicle speed, fuel level, engine temperature and oil pressure, as well as the odometer, as shown in Figure 1. This information, vital to the driver, remains in the instrument cluster of modern vehicles; however, new technological advances are leading to new capabilities.

The instrument cluster, while maintaining a traditional look, is now powered by a microcontroller (MCU) that reads vehicle status information from a Controller Area Network (CAN) bus. Drivers receive information in a familiar format, but stepper motors and the cluster’s MCU control the mechanical gauges and needles. Universally recognizable “tell tale” indicator lights and an audible chime provide additional information.

Figure 1: An analog cluster consisting of six mechanical gauges

As electronic technology advanced, the odometer was replaced with an alphanumeric display that highlighted functions and information such as fuel efficiency, outdoor temperatures and trip length, while maintaining the traditional information display through electromechanical gauges. This type of hybrid cluster with informational graphics support, shown in Figure 2, is inexpensive and relatively simple from an electronic standpoint. The MCU required for both the analog cluster and simpler hybrid cluster typically has integrated CAN interfaces and stepper motor drivers.

Figure 2: A cluster with a simple digital informational display and traditional mechanical gauges

While this simple digital display represented a step forward for clusters, it is quickly giving way to more immersive liquid crystal displays (LCDs) that provide the kind of information shown in Figure 3. As these displays have grown in size, the graphics displayed on them require higher levels of processing. The same MCU still resides in the cluster and provides the data interface and stepper motor control, but a separate graphics processor or system-on-chip (SoC) creates video images and graphics capabilities, enabling drivers to select the information they want displayed and in what format. Higher-performance systems, typically found in premium vehicles, also integrate active video from external cameras or provide a driver monitoring feature.

Figure 3: A hybrid cluster with active graphics support gives drivers more options for displaying information

While the basic information presented in an instrument cluster remains the same, Tier-1 suppliers and original equipment manufacturers (OEMs) must change the design of their clusters to help differentiate the look of each instrument panel from one model to the next – as well as from their competitors’ vehicles. OEMs must also keep up with consumer trends because drivers expect new vehicles to have the latest technology and features. These two factors have led to the development of the reconfigurable digital cluster, which replaces the stepper motor gauges and indicator lights with a large LCD display that occupies the space once reserved for gauges. This evolution replaces the electromechanical parts of the cluster with virtual representations that can fool drivers into thinking that the needles and gauges are still there.

Large displays place additional performance requirements on the processor. In order to digitally animate a speedometer, the cluster video display needs fast frame rates in order to present an image representing a needle or a bar graph that appears to move smoothly. Of course, more power is required to sustain such a system.

The advantage for Tier-1 suppliers and OEMs is that a single, scalable electronics platform provides cluster differentiation between vehicles. Tailoring the visual content presentation lets drivers select the cluster arrangement they find most appealing or useful. This functionality can also be integrated with the rest of the infotainment system, with the cluster becoming a remote display system. Reconfigurable digital clusters like the one shown in Figure 4 are currently found primarily in premium vehicles, but as production volumes increase, production costs will decrease and this type of cluster will appear in more mid-market and economy vehicles.

Figure 4: Example of a reconfigurable digital cluster

As you can probably tell after reading this post, vehicle instrument clusters have undergone tremendous changes in the last several years, as the analog cluster gives way to digital electronics. Along with it, increasing complexity has led to more design challenges. Whether your cluster design is analog, digital or a mix of both, TI’s technical resources will help reduce design time and system complexity.

Additional resources

• Learn more about TI’s infotainment and cluster solutions.
• Read more about infotainment and cluster solutions in the blog post, “The road to today’s digital cockpit.”
• Read about the important role processors play in digital cockpits in the blog post, “Jacinto™ DRA automotive processors drive digital cockpit solutions.”
• Read more about TI’s Jacinto DRAx infotainment processors in the white paper, “Jump Start Upgrading Your Digital Cluster Design with Jacinto™ 6 Platform.”
• Accelerate your cluster power system with the Wide-Vin, 3A Buck 2-Layer Reference Design for Automotive Cluster with CISPR 25 Class 5 Compliance

Anyone who uses a battery-powered product or device can appreciate the importance of an accurate battery-capacity indicator. It can be very frustrating to have your device suddenly die without any warning.

Traditionally, the simplest method of indicating battery capacity was to measure the battery voltage with an analog comparator and generate a simple low-battery warning below a predetermined threshold. In products that already have a general-purpose microcontroller (MCU), an analog-to-digital converter (ADC) can make a more accurate (digital) voltage reading, compare that reading to a set of predefined levels, and generate a more sophisticated battery-level indicator.

But if you look at the voltage profile of an actual battery in an application with variable load conditions, you will soon learn that a simple voltage-based reading can be very misleading. Assume that a single-series cell-powered system needs to be alerted when the battery voltage is 3.7V, which is based on an open circuit voltage (OCV) of about a 15% state of charge (where 0% is empty and 100% is full). The challenge is that battery voltage may cross 3.7V several times before settling. The system may alert the end user too early and shorten the run time or issue an alert too late and allow the system to crash, potentially even damaging the hardware.

Figure 1 is an example of the same battery responding to dynamic loads at different temperatures. Using a lower current at cold temperatures helps drain out all of the battery’s capacity. The depth of discharge (DOD) (DOD = 1 – true state of charge) normalizes the X axis. The voltage responses appear to be two different animals!

Figure 1: Battery-voltage response to dynamic loads at different temperatures

Aging is another concern. Once the present full capacity of the battery is below 80% of its original full capacity due to aging, it’s going to spiral down to its end-of-life state very quickly. For an aged battery, a voltage = 3.7V may indicate almost no remaining capacity.

In many cases, a generic MCU’s ADC accuracy is typically not good enough for an accurate state-of-charge calculation. For some batteries, 1mV error converts to a 1% state-of-charge error. Figure 2 is an example where ±20mV accuracy means a 20% state-of-charge error in the flat region, assuming that you need OCV.

Figure 2: DOD percent error caused by OCV reading error

Furthermore, the general-purpose MCU in a system may have many functional blocks and numerous other tasks going on in parallel. It may not be the most power-efficient solution or the most accurate battery-level indicator. But by adding a small external application-specific fuel-gauge device, you can get a more accurate and power-optimized solution.

If the portable device spends a significant amount of time in an idle/low-power state, the main MCU (which could consume more power than a dedicated gauge device) does not have to wake up and consume power just to check on the battery condition. While it can take the MCU several milliamps to measure and calculate the state of charge, a discrete gauge consumes only a small fraction of what an MCU would have consumed– the average current is 20 to 30µA with sleep mode on. With proper power-management techniques, it can even drop to <2µA.

TI’s discrete gauge hardware is specifically designed for battery management. The gauge device takes accurate measurements with minimum power consumption. However, without a proper battery model and supporting gauge algorithm, the measurements are only a reflection of the present moment. The TI models and gauge algorithm comprehend the electrochemical features of many different kinds of batteries and have been proven in many millions of systems in the field.

In addition, TI discrete gauges provide added functionality such as black-box battery forensics, health indication and smart charge control. An accurate gauge device helps bring power management to another level for an enhanced customer experience.

Last but not least, a percentage prediction adds sophistication and intelligence to the product, and instantly improves the end-user experience.

If you’re trying to find the right fuel gauge to your design, try searching our portfolio of gauges.

Additional resources

• Watch a training video on using gauges.

• If you have questions on designing with fuel gauges, search for support here. Explore TI’s battery fuel gauge portfolio, with discrete gauges, protection integrated gauges and battery management units.

What is the first thing that comes to mind when you hear the phrase “capacitive touch”? I’d be willing to bet that the first thing that popped into your head was a touch screen. You may have thought about your smartphone, that tablet computer you wish you had, or a fancy infotainment system in a new car. You’d be right on all accounts, but what you would be missing are the many products you use every day that also implement capacitive touch – just in a simplified way.

The same technology used to implement a capacitive touch screen in a smartphone is trickling down into other products such as new home appliances, electronic locks and music players. Why? It’s really quite simple. In today’s marketplace, a product’s aesthetic quality has become more important than ever. Long gone are the days of beige-colored computers and corded telephones. Capacitive touch creates freedom for designers and marketing professionals to rethink a product’s user interface, shape and mechanical construction, and improve both aesthetics and functionality.

Figure 1 shows an example of a thermostat with a simple capacitive touch interface. Because there’s no need for mechanical buttons, the front of the thermostat can be completely seamless, with no moving parts or cutouts for push-buttons. Taking out the moving parts and using a one-piece enclosure can improve long-term reliability and electrostatic discharge (ESD) tolerance, respectively.

Figure 1: A thermostat with basic capacitive touch sensing

Swapping out a mechanical switch or push-button for a capacitive touch button has not always been a trouble-free process. There are increased up-front software development and qualification costs, as well as recurring integrated circuit (IC) costs. To address these limitations and increase adoption of capacitive touch buttons, TI launched its CapTIvate™ touch technology and development ecosystem in 2015. CapTIvate technology lowers software development costs and reduces time to market for designers, thanks to the CapTIvate Design Center drag-and-drop sensor creation environment with built-in visualization tools, tuning tools, data logging, documentation and source-code generation.

Figure 2: CapTIvate Design Center sensor canvas and data visualization views

The ability to get started without having to write a line of code or become an expert in capacitive sensing has removed the upfront development cost barrier. However, adding a touch sensing microcontroller (MCU) has still been cost-prohibitive for a simple product with just a few buttons. If you’re designing a simple product with only one or two buttons, you may have had a hard time justifying the added expense of touch sensing.

Now, TI is removing the IC cost barrier by expanding the CapTIvate touch sensing MCU portfolio to include MSP430FR2512 and MSP430FR2522 touch sensing MCUs. The MSP430FR2512 MCU can support as many as four capacitive touch buttons. It’s a good fit for products with simple user interfaces such as elevator call buttons, computer monitors and TVs. If you need more than four buttons for something like a wireless speaker or electronic access control product, the MSP430FR2522 MCU supports up to eight self-capacitance buttons or 16 mutual capacitance buttons. The MSP430™ CapTIvate Touch Keypad BoosterPack makes development with the MSP430FR2522 a snap.

Figure 3: MSP430 CapTIvate Touch Keypad BoosterPack for the MSP430FR2522 MCU

The new MSP430FR2512 and MSP430FR2522 MCUs have the same differentiating capacitive sensing performance as the rest of the CapTIvate portfolio, just in a smaller package and at an appealing price point.

Additional resources

• Learn more about CapTIvate technology.
• For technical support, see the TI E2E™ Community MSP Low-Power Microcontrollers forum.
• Watch the video series on the BOOSTXL-CAPKEYPAD features and out of box demos. 

We’ve covered a lot of material in this electrostatic discharge (ESD) fundamentals series, such as the International Electrotechnical Commission (IEC) 61000-4-2 rating, the ESD clamping voltage and junction capacitance. In this final installment of the series, I’ll cover a few more important ESD parameters: reverse working voltage, breakdown voltage and polarity configuration.

Recall that once the voltage exceeds a certain threshold, the ESD diode will break down and present a low-impedance path to redirect current to ground. During normal operation, however, the ESD diode should be completely “off” and not interfere with the signal or power passing through the trace. This normal operating voltage range is referred to as the reverse standoff voltage or reverse working voltage (V_RWM). The V_RWM is defined as the maximum positive and negative voltage where current flowing through the diode does not exceed a certain amperage. For several of TI’s newest ESD diodes, this amperage is specified at 10nA. Once the voltage exceeds V_RWM, it approaches the breakdown voltage (V_BR), which is defined as the voltage where current through the diode exceeds 1mA (Figure 1).

Figure 1: Logarithmic I-V curve of an ESD diode with V_RWM and V_BR

It is crucial to select an ESD diode with a V_RWM that encompasses the interface’s entire voltage range to minimize leakage current during normal operation. When doing this, it is important to pay attention to the polarity configuration of the diode. ESD diodes come in two configurations, as listed in Table 1.

Table 1: Polarity Configuration Comparison

Figure 2: I-V curves for a unidirectional ESD diode (left) and a bidirectional ESD diode (right)

After covering quite a bit in this ESD fundamentals series, let’s use everything you’ve learned to select a suitable ESD diode to protect a USB 2.0 system that fails at a 19V transmission line pulse (TLP) (here’s a refresher on TLP and clamping voltage).

• USB 2.0 differential signals have a voltage range of approximately 0V (logic low) to 3.6V (logic high), so you want to make sure that your diode’s V_RWM encompasses this range.
• USB 2.0 bandwidth can reach up to 480Mbps, so you want to select a diode that has the appropriate capacitance to maintain signal integrity.
• You need to meet IEC 61000-4-2 level 4 compliance, so the ESD diode must be rated for at least 8kV contact discharge and 15kV air-gap discharge.
• The clamping voltage of the ESD diode at a 16A TLP must be less than 19V, since the system will fail at 19V.

The TPD1E04U04 is a good solution because it meets all of these requirements:

• It’s a unidirectional ESD diode that has a VRWM of 0 to 3.6V.
• It has a low capacitance of 0.5pF.
• It has an IEC 61000-4-2 rating of 16kV contact and 16kV air gap.
• The clamping voltage is 9V at a 16A TLP.

This installment concludes the ESD fundamentals series. Feel free to leave a comment below or post on the TI E2E™ Community Circuit Protection forum if you have any questions. Happy ESD hunting!

Additional resources

• For more information on ESD selection, check out the “System Level ESD Protection Guide”
• Read Roger Liang’s Analog Applications Journal article, “Design considerations for system-level ESD protection.”
• Check out the application report, “Reading and Understanding an ESD Protection Datasheet.”

There's a lot riding on the next generation of industrial infrastructure. Creating stable and trustworthy devices for the Internet of Things (IoT) takes more than just having a wireless network connection. The smart devices that guide and drive everything from road sensors to power turbines need to be cloud-enabled, flexible, remotely managed and extremely secure. Gartner estimates more than 8.4 billion "things" are on the internet today, up more than 30 percent from just one year ago.

This requires highly capable, low-power microcontrollers (MCUs) running a feature-rich real-time operating system (RTOS) that easily connects to the cloud. To meet those demands, our company has worked with Amazon Web Services (AWS) to bring Amazon FreeRTOS to the TI SimpleLink™ MCU platform, which enables customers to  focus on their application development and connect quickly to the cloud while leveraging advanced security features.

Microcontrollers frequently run operating systems that do not have built-in functionality to connect to local networks or the cloud, making IoT applications a challenge. Amazon FreeRTOS helps solve this problem by providing both the core operating system (to run the edge device) as well as integrated software libraries, from the SimpleLink SDK in this case, that make it easy to more securely connect to the cloud – or other edge devices – so you can collect data from them for IoT applications and take action.

“The combination of Amazon FreeRTOS, the AWS services and the TI SimpleLink CC3220SF wireless MCU provides a complete solution for building more secure IoT devices that deliver on the promise of smart products,” said Mattias Lange, general manager of our company’s Embedded connectivity solutions group. “The CC3220SF is the most feature-complete wireless MCU on the market, providing a cost-effective single-chip solution for both Wi-Fi and MCU applications.”

Cloud acceleration

Few RTOSs today provide solutions with integrated networking and connections to cloud services. The cloud is a critical piece to the growth of IoT because access to cloud storage and processing enables IoT devices – from autonomous mining drills to self-driving vehicles – to function in small and low-power applications.

Combining Amazon FreeRTOS and the TI SimpleLink CC3220SF wireless MCU is a great way to accelerate development of IoT applications in the market, thanks to careful integration. They combine comprehensive, modern security capabilities that include secure storage and protected bootloaders, which prevent tampering. Trusted authentication and configuration of authorized new devices make it easier to add new devices over time. And protected over-the-air updates of device firmware let customers keep devices up-to-date, patched and configured for changing application requirements needs.

Our CC3220SF wireless MCU is uniquely well-suited to meet all these demands because of its dedicated network processor and cryptographic engine. Memory and processing power is always a scarce resource in any MCU device. Offloading these key networking and security operations to integrated hardware frees up more processor power and memory for core tasks instead of tying them up in the operating system layer.

The next big thing

The introduction of Amazon FreeRTOS and the launch-day certification of our company's MCUs on the new platform are significant developments for an already-strong RTOS platform. While there are many real-time operating systems in the market, the FreeRTOS kernel has been one of the consistent market leaders.

Building the new wave of IoT innovation

It's easy to get started with Amazon FreeRTOS and SimpleLink MCUs. The software has been built integrating the SimpleLink SDK core features and is an open-source solution with no additional license or user fees available directly from AWS. The TI SimpleLink SDK, also available online under an open source license, adds additional examples and drivers for further application development. That means no unpleasant surprises when an inspiring new idea turns into a prototype IoT application, and that prototype gets ready for prime time.

The AWS cloud is primed to amplify a new wave of IoT devices. AWS provides a configuration console to make it easy to get started developing IoT solutions with the new software and our company’s SimpleLink LaunchPad™ development kit. The only thing missing? Your ideas.

Read more about the possibilities for IoT development on TI devices.

Automobiles are becoming more advanced every day. The number of integrated circuits (ICs) is increasing every year and spreading to more modules within the automobile to control lights, heating, sensors and more. The new paradigm of designing automobiles with more features and electrical controls raises the question of whether this is safe, and whether ICs can withstand the voltage transients common in automotive environments.

Of course, if you apply a 12V power supply to a microcontroller requiring a 3.3V supply, the device will not operate correctly and you run the risk of catastrophic failure. The same principle applies to transients in the automotive environment, whose voltages can rise (or become negative) far beyond the specifications of the ICs. Transients are even more severe in 24V-battery systems like commercial trucks, forklifts and mass transit vehicles.

Nearly every car in the world uses the Local Interconnect Network (LIN) protocol. Modules that use LIN connect directly to the car battery through a diode; LIN transceivers that send and receive data across the LIN bus experience transients all the time. It is vital that you choose a LIN transceiver that is sufficiently protected from transients so that different modules in the car can communicate effectively. Figure 1 shows the most common automobile transients.

Figure 1: Common automobile transients

At the top of the dangerous transients list is the load dump, also known as a battery disconnect from the alternator. The alternator (the voltage source) is delivering charging current to the battery (the load). Due to the large inductance in the alternator and the drastic change in load current due to the battery being disconnected from the system in a short amount of time, there is a large voltage spike that all the remaining nodes connected to the alternator will see (V = L*di/dt). These voltage spikes can range anywhere from 25V to 120V, as shown in Figure 1. While this is a relatively short transient (milliseconds), some transients can last for several minutes.

Jump-starting a car is something most drivers have experienced. Jump-starts can be detrimental to ICs and electrical devices inside. The voltage regulators are intending to step down or step up automobiles supplied with a 12V battery (or a 24V battery in commercial vehicles). Roadside service vehicles typically use 24V batteries (or 48V batteries for commercial vehicles) to jump-start cars; this means your car is receiving two times the expected voltage. Electronic devices in the car may be exposed to this transient for up to five minutes as the jump-start procedure concludes.

The new TLIN family of LIN transceivers has robust performance in both 12V consumer and 24V (or higher) commercial vehicles. You can directly connect ICs to the system battery and provide communication between all modules in the car. They are built to withstand transients (load dumps), have a wide operating range (for jump-starts) and include DC fault protection (for reverse-battery) while increasing the speed and reliability of the LIN bus. Check out the TLIN2029-Q1 to learn more about 24V application capabilities.

Additional resources

• Learn more about LIN and how it solves problems in automobiles in this blog, “LIN – The Last Mile Network”

Imagine waking up, and using a voice command to turn on your lights and start your coffeemaker. As you leave for work, you use your smartphone to lock the door and arm your security system. While you’re away, you can remotely monitor intrusions, answer your doorbell and unlock your front door, all from a cloud dashboard. At work, a smart thermostat collects data from remote temperature sensors throughout the building and controls the climate in each individual room, saving energy and optimizing the environment for each user. Outside the office walls, thousands of messages fly through the air, reporting grid data from electric meters, water meters, streetlights and more.

This isn’t a science fiction movie – it’s today’s reality. Homes, buildings and cities are becoming more and more connected, but connectivity is hard, and as more devices become “smart,” design complexity continues to increase. Connected devices must be scalable and secure enough to keep up with the changing landscape while maintaining low power and high feature integration for long product lifetimes and expanded application coverage.

TI’s mission is to make connectivity easy for designers and developers with the SimpleLink™ microcontroller (MCU) platform, the largest portfolio of Arm®-based MCUs with 100% code compatibility between devices. Here is what you need to know about the newest devices in the SimpleLink platform:

• More connectivity standards.When the SimpleLink platform launched, it supported Wi-Fi®, Bluetooth® low energy, Sub-1 GHz, dual-band operation and host MCUs. The newest SimpleLink devices add support for Thread, Zigbee and multistandard (SimpleLink CC2652R), in addition to enhanced devices for Bluetooth 5 (SimpleLink CC2642R), Sub-1 GHz (SimpleLink CC1312R), multiband (SimpleLink CC1352R) and host MCUs (SimpleLink MSP432P4). The breadth of connectivity standards enables developers to create more scalable and future-proof products to keep up with the demands of the connected landscape. Figure 1 shows the complete portfolio of SimpleLink devices.

Figure 1: The devices of theSimpleLink MCU platform 

• More design flexibility.With the addition of multiband and multistandard support on a single device (the SimpleLink CC1352R or CC2652R), design flexibility for applications continues to become more scalable. Through time-division multiplexing, you can take advantage of the benefits of multiple connectivity technologies using a single device. Leveraging SimpleLink software development kit (SDK) wireless plug-ins also enables a seamless transition between single- and multichip designs. Take, for instance, a smoke alarm system in a commercial building. The smoke alarm nodes can connect to the main security panel through a long-range Sub-1 GHz star network, taking advantage of the increased range and ability to penetrate walls. At the same time, it’s possible to turn the smoke alarms on or off, advertise their status, or perform upgrades or maintenance using a Bluetooth 5 connection with the user’s smart device.

• Lower power operation.The new SimpleLink wireless devices have excellent power performance, with standby current consumption as low as 0.8µA with 80KB of random access memory (RAM) and central processing unit (CPU) retention. However, the key differentiator for low-power operation is the sensor controller engine. The sensor controller is a digital core with 4KB of RAM, which allows the main system to sleep until an event trigger from sensor controller peripherals (12-bit analog-to-digital converter [ADC], comparator, Serial Peripheral Interface [SPI]-I²C, time-to-digital converter) wakes it up. For example, the sensor controller can operate as low as 1µA while completing an ADC sample every second. This enables connected devices to operate at ultra-low power while still monitoring sensor data, which extends the lifetime of products that run on small coin-cell batteries. Figure 2 is the full SimpleLink CC1352R wireless MCU block diagram.

Figure 2: Block diagram of SimpleLink CC1352R wireless MCU

• More integration.The newest SimpleLink platform wireless devices have an integrated Arm Cortex-M4F paired with 352KB of flash, 80KB of RAM and 256KB of read-only memory (ROM) with integrated components of protocols and firmware to optimize customer application space in flash. Additionally, the platform has the option for an integrated +20dBm power amplifier (PA) to enable higher power output for metering and building automation applications. The new SimpleLink devices also feature security enablers to make it easy to design secure applications. The devices include an Advanced Encryption Standard (AES)-128/AES-256 crypto accelerator, elliptic-curve cryptography (ECC) and a Rivest-Shamir-Adleman (RSA) public key hardware accelerator, a Secure Hash Algorithm (SHA) 2 accelerator (up to SHA-512), and a true random number generator. As more connected devices enter our homes, buildings and cities, these new features enable you to expand into more applications with greater integration and build secure applications to protect personal data.

• More hosting.The SimpleLink platform is expanding SimpleLink MSP432P4 host MCUs with the lowest-power 2MB MCU in order to manage multiple wireless communication stacks, human machine interfaces (HMIs) and firmware images. SimpleLink MSP432P4 MCUs are low-power 48MHz Arm Cortex-M4Fs with precision analog-to-digital converters (ADCs) including 16-bit performance, new enhanced lower-power peripherals and serial interfaces, a 320-segment liquid crystal display (LCD) and as many as 84 general-purpose input/output (GPIO) pins. In addition, these MCUs are completely pin-to-pin compatible with existing MSP432P4 products, enabling scalability from 128kB of flash all the way up to 2MB of flash and 256kB of static RAM. A suite of wireless plug-ins in the SimpleLink SDK makes pairing SimpleLink wireless MCUs to the SimpleLink MSP432 host MCU simple.

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Additional Resources

• The SimpleLink multi-standard CC2652R wireless MCU (Thread, Zigbee, Bluetooth 5)

• • Get started with the LAUNCXL-CC26X2R1 LaunchPad development kit and the CC26X2 SDK.

• The SimpleLink Bluetooth 5 CC2642R wireless MCU

• • Get started with the LAUNCXL-CC26X2R1 LaunchPad development kit and the CC26X2 SDK.

• The SimpleLink Sub-1 GHZ CC1312R wireless MCU

• • Get started with the LAUNCHXL-CC1312R1 LaunchPad development kit and the CC13x2 SDK.

• The SimpleLink multiband CC1352R wireless MCU (Sub-1 GHz + Bluetooth low energy, Thread, Zigbee)

• • Get started with the LAUNCHXL-CC1352R1 LaunchPad development kit and the CC13x2 SDK.

• The SimpleLink MSP432P4 MCU (low power, precision ADC)

• • Get started with the MSP-EXP432P4111 LaunchPad development kit and the MSP432 SDK.