Co-authored by Bhargavi Nisarga, Systems Engineer at TI

You’ve already started to develop your own smart thermostat by implementing the sensing and measurement chain for your application. Now, let’s get going with processing and logging the digital sensor data.

Assuming that you have your analog-to-digital converter (ADC) up and running to sample the measured data, you might wonder what options you have to further work with this data. This third installment of a seven-part series will touch on three steps:

1. How to transfer data from one memory address to another.
2. How to perform further data processing to get meaningful information for your application.
3. How to store the relevant data.

Figure 1 shows a simplified microcontroller (MCU) block diagram with a central processing unit (CPU) and direct memory access (DMA) controller as the bus masters in the system.

Figure 1: High-level block diagram of a typical MCU

There are a few different data-flow scenarios involving the transfer of ADC data to on-chip and off-chip components:

•  The ADC data is transferred via CPU or DMA to on-chip nonvolatile memory (NVM) storage.
• The ADC data is transferred via the CPU or DMA to an on-chip RAM. In this case, data can be further processed and then moved to on-chip NVM, or to the serial communication buffer via the CPU or DMA. Data can also move to external off-chip components via serial communication modules.
•  The ADC data is transferred to a serial communication peripheral directly via the CPU or DMA.

In the case of our smart thermostat application, let’s focus on the second data-flow scenario, involving some data processing and averaging before sending the temperature measurement information to an external system, like a connectivity device that in turn connects to the cloud. On the other hand, if you want to collect a large amount of data to perform data analytics (for example, analyzing averages or minimums/maximums over time), you transfer measured data to an external system and then do the processing (such as cloud computing).

Now, let’s get started with the data transfer.

How to move the (conversion) data

The second installment of this series provided information on conversion-mode options for ADC configuration. Most likely, you opted for the single conversion mode and thus have only one conversion data after every timer trigger. In typical MCU systems, you have two options to move the data from one memory address to another: by either using the CPU (Figure 2a) or DMA (Figure 2b). The advantage of using DMA is to perform the data transfer without involving (or even waking up) the CPU. Thus, you can save energy using DMA in a low-power mode while the CPU is sleeping.

Figure 2: Data transfer executed by the CPU (a); data transfer executed by DMA while the CPU is sleeping (b)

For smaller data sizes, DMA is not absolutely necessary, but it is still an option. You can opt to use the CPU or DMA to move the data to memory every time you take an ADC measurement. For transferring larger data sizes (for example, transferring all data collected in one day to a cloud or to external memory for backup), consider using DMA.

To configure the DMA, you need to set the right DMA transfer mode, distinguishing the transfer of a single data point or block of data and selecting whether it is acceptable to allow block transfer with CPU activity interleaved. Configure the size and width (byte/word/long word) of the data being transferred, plus the source and destination address of the transfer. Afterwards, just select the signal that will trigger the DMA transfer and you can start.

In a temperature-monitoring application, you will typically average multiple data points during measurement. In that case, you can use DMA to move the amount of data you want to use for the average and only wake the CPU after the transfer of all of the data points.

Smart conditioning – how to process the data

The second installment of this series outlined various temperature sensors, with the final decision to go with the thermistor option. The ADC conversion results represent the thermistor analog values in a digital format. In order to retrieve a meaningful temperature value, you need to apply the voltage-to-temperature formula to the conversion result. Thermistors come in various sizes, are very sensitive to temperature changes and easy to interface with MCUs. However, since the thermistor response to temperature changes is very nonlinear, correlating the thermistor voltage to an actual temperature value entails either computing the nonlinear transfer function or using a look-up table (LUT)-based approach. The LUT-based approach requires using linear extrapolation between two temperature points in the LUT to interpret the temperature.

Thermistor data sheets typically include a temperature-to-respective thermistor resistance LUT for several temperature points. Using the table in the data sheet, for a given temperature value you can determine the actual analog voltage present at the ADC input channel. This analog input value correlates to a specific ADC code. The blog post, “It’s in the math: how to convert ADC code to a voltage (part 1)” discusses analog-to-digital conversion parameters in detail.

The LUT stored on the MCU will include a list of temperature points mapped to the respective ADC digital codes. Upon taking a specific temperature measurement using the on-chip ADC, the application firmware can determine between which two temperature points the measured digital code falls into within the LUT. Once you know this, you can extrapolate the temperature value between the two points using the point slope formulae. The point slope formulae involve multiply-and-divide operations that can be computationally intensive, requiring a lot of CPU cycles. Consider MCUs where some of the computations are handled in hardware, which then requires less CPU involvement and enables faster and more energy-efficient computation. For example, many MSP430™ MCUs have a hardware multiplier that can enable 8-, 16-, 24- and 32-bit operations and achieve multiplication results within a few clock cycles.

If required, you can also consider averaging the temperature values measured before using the LUT. For averaging values in the order of multiples of 2, consider using shift-right instructions, which are less computationally intensive.

How to store data without losing it at power loss

In order to not lose data upon power loss, you will need to store it in NVM. MCUs typically offer embedded NVMs to store your code and data.

In most cases, MCUs offer flash memories to store your data when there is no power to the device. The data access – irrespective of if you want to read, write or erase – is blockwise and handled in blocks of 64B, 128B, etc., based on device. The main disadvantage is the limited number of writes/erases (dependent on technology between 3,000 and several 100,000 cycles).

TI offers microcontroller families with embedded FRAM NVM. These families offer faster memory access (especially when writing), unified memory access (that is, no blockwise access), lower energy consumption compared to flash writes (as charge pump is not involved for erase/write operations) and increased write/erase endurance compared to flash. Since FRAM memory has faster write access times and does not require erasing the memory before writing, it enables faster writes to store data during a power-loss event. Faster writes reduce the time that interrupts are delayed or even blocked in your system.

As a wrap-up, here are the key takeaways of the third installment of this series:

• In typical MCUs, you can either use the CPU or DMA to transfer data from one memory to another.
• Data processing on-chip can be computationally intensive. Consider hardware features and accelerators, which enable faster and more energy-efficient computations.
• On-chip and off-chip NVMs can store data in the system. If you want to store data without losing it at power loss, consider MCUs with FRAM NVM.

Stay tuned for the fourth installment of this series, which will cover the human machine interface.

Additional resources

• Read the first and second installments of this series:
  • “How to build a smart thermostat using an MCU – 7 steps to make it happen!”
  • “Step 2 to build a smart thermostat using an MCU – It’s all about the sensing.”

• Seethe MSP430 MCU and MSP432 MCU Users Guides for more details on how configuring DMA works.
• Check out the different types of TI temperature sensors.
• Get more details about FRAM and its benefits:
  • Understanding FRAM Technology
  • “MSP430 MCUs feature FRAM with a touch of security.”
  • “What is compute through power loss?”
• Download this reference design: Intelligent System State Restoration after Failure with Compute Through Power Loss Utility

Consumer applications often require power supplies to support an adjustable output voltage for different operating conditions such as USB Type-C™. This demand creates the need for a simple and effective method to tune the output voltage. There are many ways to interact with the feedback (FB) pin on the integrated circuit (IC) to set the desired output. One way is to add a trim resistor at the FB pin, and apply a voltage to source or sink additional current at the FB pin’s resistive divider. Another approach is to use an I²C bus to program signals to interact with the FB pin. But what if a variable voltage source or I²C bus is not available? In this post, I will show you how to use a simple resistor capacitor (RC) low-pass filter, a trim resistor and a pulse-width modulation (PWM) signal from a microcontroller unit (MCU) to tune the output voltage.

Figure 1 shows the circuit illustration of this approach.

Figure 1: PWM injection circuit

The RC low-pass filter will average the PWM signal based on the duty cycle. The Thevenin equivalent of the circuit in Figure 2 and the filter capacitor will create the time constant, which determines the slew rate of the signal injected into the FB pin. Equation 1 shows the calculation:

Figure 2: Thevenin equivalent

Because the added RC filter introduces a pole and zero pair into the overall control loop, you will need to take care when selecting the RC filter. Looking again at Figure 1, at low frequency, when C_lowpass is open, the sum of R_inject and R_lowpass is in parallel with R_fbb. When C_lowpass shorts at high frequency, only R_inject is in parallel with R_fbb. Therefore, selecting R_lowpass to be much smaller than R_inject will ensure that the pole and zero pair is close to each other and will minimize the effect on the controller’s control loop.

Equations 2, 3 and 4 calculate how to best select the injection, top and bottom FB resistors, respectively:

Equation 3 corresponds to the minimum output voltage, and Equation 4 corresponds to the maximum output voltage.

For example, if the available 3.3V PWM signal’s duty cycle varies from 6% to 94%, you would select a 49.9kΩ top FB resistor and a 1kΩ R_lowpass to achieve a 1V-to-10V output, and your controller’s FB voltage would be 0.8V. Equations 5 and 6 show the calculations of R_fbb and R_inject:

Setting Equations 5 and 6 as equal, R_adj yields 16.47kΩ and R_fbb yields 5.41kΩ when selecting a standard value of 15.4kΩ and 5.36kΩ for R_inject and R_fbb, respectively.

The controller’s duty cycle will be perturbed if a lot of ripple is injected into the FB pin; therefore, you will need to take some care when selecting the low-pass filter’s capacitance. As a good design practice, maintain less than 1% ripple on the FB pin voltage – much less. For example, with a switching frequency (F_sw) of 200kHz, use a PWM of 1MHz with an RC time constant of 1ms. This will minimize any beat-frequency components appearing on the output voltage. R_lowpass and C_lowpass will dominate the time constant, since the resistors at the FB divider side have a much higher impedance than R_lowpass.

Following the design methodologies described in this post will reduce development time and circuit complexity for applications requiring multiple outputs.

Additional resources

• Check out these reference designs:
  • • 9 to 42VIN 5V/12V/20V at 5A Synchronous Four-Switch Buck-Boost Converter Reference Design.
    • Four-Output USB Type-C™ 100W Buck-Boost Reference Design.

Home automation has grown tremendously in recent years thanks to the accessibility of wireless technologies and – more importantly – the standardization of previously diverging standards and protocols. One standardization effort is Apple’s HomeKit technology, a framework that defines a common protocol and environment where HomeKit enabled systems work by the same rules, ensuring device interoperability.

HomeKit technology’s level playing field enables you to worry less about the framework and gain valuable time to spend making your end products stand out from competition. Taking it a step further, TI’s Bluetooth® low energy HomeKit solution features the MSP432™ host microcontroller (MCU) and SimpleLink™ CC2640 Bluetooth low energy wireless MCU in wireless network processor (WNP) mode (Figure 1), delivering both a HomeKit enabled solution and tons of highly differentiated features to help you set your products apart.

Figure 1: MSP432 MCU + CC2640 wireless MCU HomeKit applications

The MSP432 host MCU in TI’s Bluetooth low energy HomeKit solution runs the HomeKit Accessory Protocol (HAP) driving the CC2640 wireless MCU, which operates in WNP mode via the universal asynchronous receiver/transmitter (UART) serial interface. A dedicated wireless connectivity processor offers robust Bluetooth low energy connectivity with industry-leading radio-frequency (RF) performance for excellent in-home coverage at low power consumption. If you value time to market, TI offers a pre-certified module option (CC2650MODA) that simplifies integration, as you can virtually drop in the module running as a black-box Bluetooth low energy WNP and focus your energy solely on your application.

With the Bluetooth low energy stack taken care of, the MSP432 MCU offers an additional 48MHz ARM® Cortex®-M4F central processing unit (CPU) to run the HomeKit stack, with plenty of memory space and CPU bandwidth left for your application. And adding software to MSP432 MCU is now simpler than ever. The SimpleLink MSP432 software development kit (SDK) is a single software entry point with intuitive and abstracted application programming interfaces (APIs); a power-optimized real-time operating system (RTOS); and a rapidly growing collection of middleware and plug-ins that further expand the capabilities of a system including graphics display, advanced algorithms such as a speech recognizer, and interfacing with a wide range of sensors, actuators and human machine interface (HMI) elements.

The MSP432 MCU integrates a 1MSPS successive approximation register (SAR)-based analog-to-digital converter (ADC) that can achieve up to 16 effective number of bits (ENOB). You can bring high-quality, high-resolution analog sensor signals directly into your system without an external ADC. These advanced analog capabilities in a tiny and integrated solution for applications such as glass-break detectors, indoor weather stations and air-quality monitors. These features are the special sauces that could help you build a unique product, not just another home automation solution.

Let’s take a deeper look at how the TI Bluetooth low energy HomeKit solution works.

The MSP432 SDK HomeKit plug-in is available as a complementary software package for the SimpleLink MSP432 SDK, providing all of the software you need to implement a HomeKit accessory. Specifically, the MSP432 SDK HomeKit plug-in provides a complete implementation of the HAP, pairing and administration services, security services including cipher, signing, and key management, and example accessories to help developers get started quickly.

With all key HomeKit components taken care of, original equipment manufacturers (OEMs) can focus on implementing the specific features of their product by leveraging the software components from the SimpleLink MSP432 SDK, the foundational layer of the software architecture. As illustrated in Figure 2, the SimpleLink MSP432 SDK offers a rich set of features including:

• Common foundation of drivers, frameworks and libraries
• Pre-integrated TI-RTOS kernel already deployed in thousands of products across multiple applications
• POSIX compliant API ensures compatibility with numerous third-party software components RTOS multitasking kernel and device drivers.
• MSP432 graphic libraries, display drivers, and several other peripheral and application libraries to extend functionality for your products

Figure 2: SimpleLink MSP432 SDK Block Diagram

To demonstrate the capabilities of the Bluetooth  low energy  HomeKit solution, we created an example accessory of a HomeKit enabled lighting control panel.  A color 320x240 pixels (QVGA) Liquid crystal display (LCD) is used for various Human-Machine Interface (HMI) interactions. The MSP432 host MCU leverages its integrated 14-bit ADC and SPI modules to control the touch-enabled LCD.  The system block diagram of the example is illustrated in Figure 3 below.

Figure 3: Bluetooth low energy HomeKit enabled Lighting control panel block diagram

A user can use an iOS-based device with the native Home app to authenticate the accessory and control the light on the accessory. The LCD is used in several functions: to indicate the light status via the lightbulb icon, local HMI capabilities when an iOS device is not available for HomeKit interaction, and lastly as an interesting method to authenticate the accessory via scanning the authentication code on the LCD into the iOS device’s camera. In this example , the entire system consumes less than 3µA in standby mode (low-power mode 4 or LPM4)  without the LCD display, uses 138kB of flash memory (and an additional 50kB of flash used for images) and 11kB of RAM.

HomeKit APIs are consistent across all of TI’s SimpleLink SDK plug-ins for HomeKit, and independent of whether you use the Bluetooth low energy or Internet Protocol (IP) transports. This means that you can easily move your application between TI platforms, from the Sitara™ processor-based Linux® IP platform, to the low-power MSP432 MCU + CC2640 Bluetooth low energy platform, and beyond into future TI devices.

TI’s development Bluetooth low energy kit consists of the following hardware:

• MSP432 LaunchPad™ development kit.
• CC2650 Module BoosterPack™ plug-in module.
• QVGA display BoosterPack plug-in module (optional).
• MFi authentication co-processor (for HomeKit development).

The MSP432 SDK BLE HomeKit plug-in offers developers with robust software building blocks to build their next HomeKit accessory. The two-chip Bluetooth low energy HomeKit solution consisting of MSP432 host MCU and CC2640 wireless network processor offers a modular hardware option that helps you accelerate development, add more differentiation to your product, and ultimately to scale and develop a wide range of home automation products with one-time software investment.

TI’s Bluetooth low energy HomeKit solution is available to MFi Licenses holders. Learn more about MFi licenses.

 Additional resources

• Learn more about TI’s Bluetooth low energy solution for HomeKit.
• Begin evaluating and differentiating your Bluetooth low energy HomeKit accessories by downloading the MSP432 plug-in for HomeKit.

Imagine traveling around the world in your car on just one gallon of gasoline. It may not be as far-fetched as you first think! A group of students from the Munich Technical University (TUM) developed and built an electric vehicle (EV) – called the eLi14 – that sips very little gasoline. In doing so, they drove straight into the Guinness Book of World Records for the world’s most efficient electric vehicle, thanks in part to their use of TI technology.

During its record-breaking journey, the eLi14 consumed 81.16 Watt-hours per 100 km, the equivalent of one liter of high-octane gasoline per 10,956 km – or enough to travel around the world on one gallon of gasoline. The test took place at a car manufacturer’s test track in Bavaria, Germany. The previous world record was set in 2005 when a vehicle traveled the equivalent of 5385 km on one liter of gasoline, which means eLi14 is almost twice as efficient.

The eLi14 electric vehicle was built by the TUfast student initiative in 2014 and modified for the world record attempt in 2016. TUfast was set up in 2002 as an extracurricular activity at TUM where students could learn in a professional environment with the associated time and cost constraints. The students also received guidance from alumni and several companies active in the EV space.

Over the years, the students developed many vehicles and competed in events such as the Shell Eco-marathon; this testing helped them develop even more energy-efficient vehicles using optimized technology that could make it onto the road in the future.

For the world record attempt, the team modified their 2014 vehicle, the eLi14, by changing several design aspects to make it lighter and optimize the control electronics. “We realized extremely accurate motor control was crucial in delivering the right amount of energy to the motor at the right time,” explained Maximilian Amm from the TUfast team.

After several unsuccessful attempts with various processors, the TUfast team turned to TI’s C2000™ Piccolo™ microcontroller (MCU) family and the TMS320F28069 MCU-based controlCARD. One of the main advantages of this development kit is the isolated debug interface on the board, which allows live debugging on a running system. This helped the team with programming and testing the motor as they could fix things on-the-fly due to the precise real-time data they received from the controlCARD.

“The ability to debug while the system was running helped accelerate the building of the motor, while the thorough testing meant we knew the car was capable of achieving the record when it hit the track,” noted TUfast team member Martin Angerer.

The C2000 MCU also measures the application of energy from the brushless DC motor and precisely processes this data in real-time. This keeps the motor running at a constant torque while using the minimum amount of energy required.

The main factor in the motor achieving maximum torque with the lowest possible demand for energy was the processor’s extremely precise pulse width modulation (PWM) control and real-time computation. This allows it to handle highly complex regulation algorithms in real time, ensuring the optimum current for the motor at any given time.

Accurate calculations and precise control signals are not enough on their own, however. The C2000 MCU is also able to adapt transistor dead time (i.e. when none of them are working) in response to environmental condition variations, such as temperature, supply voltage and output power, to minimize energy loss. When it comes to breaking records, every joule counts.

The team’s focus for 2017 is to build a new car to participate in the Urban Concept category of the Shell Eco-marathon. Using the experience and knowledge the team gained over the years, and especially from the eLi14, they are planning to build an ultra-efficient car that is more suited to public roads than its record-breaking predecessor.

In the meantime, eLi14 has reached the end of the road and will now retire. However, it will be shown at various exhibitions and tradeshows, illustrating that great things are possible when a group of talented innovators share a vision and work together to make it a reality.

Read more about TI’s technology for electric and hybrid-electric vehicles:

• The other motors in electric vehicle systems
• Driving the Green Revolution
• How we’re charging up the future of electric and hybrid automobiles
• Powering electronics in HEV and EV vehicles

Voltage supervisors have provided analog voltage monitoring to digital circuits for decades. Texas Instruments released the original TL7705 in 1983; it consumed 1.8mA, came in a plastic dual-inline package (PDIP) and you can still purchase it today. Newer supervisors come with a wide range of options, from ultra-low current (TPS3839), tiny packages (TPS3831), dual channel (TPS3779/80) and high accuracy (TPS3702) to multichannel, feature-rich power monitors (TPS38600). In addition to choosing from these options, there are some simple circuit additions that you can make to help optimize the voltage-supervisor function; here are a few of those additions.

Add a resistor to increase hysteresis

Some applications require a wider-voltage hysteresis than what is typically available with standard supervisors. One way to increase hysteresis on an adjustable supervisor is to add an additional resistor between the output pin and the input resistor divider.

In the normal configuration shown in Figure 1, R1 and R2 set the threshold voltage and R4 is a pull-up resistor. Adding R3 gives a feedback path from the output (V_OUT) to the divider voltage, allowing for adjustable hysteresis with proper resistor selection.

Figure 1: TPS3710 with resistors added for hysteresis

Equations 1 and 2 calculate the rising and falling thresholds for the circuit in Figure 1:

Sense a negative voltage

Monitoring a negative voltage can be tricky because most systems have ground-referenced logic signals, requiring level shifting to enable communication. One way to accomplish the necessary level shifting is to use open-drain outputs. Figure 2’s schematic shows how to use the TPS3700 in a negative rail with the outputs level-shifted up to give positive logic.

Figure 2:  TPS3700/1 configured for negative voltage sensing

In Figure 2, the monitored voltage (V_MON) is a negative voltage relative to ground. You can program the overvoltage and undervoltage limits with R1, R2 and R3 in the same way as for the positive voltage (see product data sheets for more information). The open-drain outputs of the TPS3700 or TPS3701 are independent of VDD, which means that V_PULLUP can be a positive voltage that enables a positive ground-referenced logic voltage to interface with any microcontrollers or processors.

Sensing a negative voltage using the previously described method requires additional diodes and resistors on the output. Another trick for sensing a negative voltage that will have fewer additional components is to use a positive voltage to shift up the resistor-divider voltages so that the divided threshold voltage is positive relative to ground. The four-channel TPS386000 supervisor makes this easy by providing a reference voltage to which you can connect the resistor chain. See Figure 3.

Figure 3: Using an external voltage reference to sense a negative voltage

In Figure 3, the V_MON(4,NEG) node represents the negative monitored voltage and V_MON(4,POS) the positive monitored voltage. Negative monitoring is possible because the resistor divider is referenced to the V_REF pin (a 1.2V output) instead of ground-referenced, as in the positive channel. The RESET output will go high in Figure 3 when the negative channel falls below -14.92V and the positive channel rises above 15.04V, nominally.

Add a P-type JFET to remove false low-voltage output signals

Most supervisors require a certain amount of voltage on VDD before the device’s output can give an accurate output. This voltage is typically around 800mV – below this voltage, the supervisor has no way to control the internal circuitry that’s pulling the output low or high. As a result, the output will rise up with the pull-up voltage until there is enough headroom for the device to pull it back down. Many times you can ignore this; however, in the cases where you cannot, you can add a P-channel junction field effect transistor (JFET ) to ensure that the output stays low even when VDD is not sufficient to provide power to the supervisor. Figure 4 shows an example.

Figure 4: Adding a JFET to remove output voltage rise with low VDD 

In Figure 4, the normal output of the TPS3890 is represented as V_G. When V_MON (the monitored voltage) rises, the voltage at V_G also rises briefly, to around 0.5V. By adding a standard JFET configured in a source-follower configuration, the voltage at the source (labeled as V_OUT) will track the voltage at V_G minus the threshold voltage of the JFET. This results in an approximate 1V drop between V_G and V_OUT, and eliminates the 0.5V rise on V_G.  Figure 5 shows the effect of using a JFET on the output of the TPS3890.

Figure 5: TPS3890 startup with and without a JFET on the output

Supervisors are necessary in a wide range of applications and systems.  While most standard configurations don’t require any additional components beyond a resistor or two, there are some applications that require additional functionality.  Hopefully this blog helps give a few ideas on how to solve these unique cases.  For more information on the circuits mentioned here, see the links below, or visit ti.com. 

Additional resources

• Get more information on supervisors and supervisor application circuits.
• For more details on sensing a negative voltage, read the application report, “Using the TPS3700 as a Negative Rail Over- and Undervoltage Detector.”
• Download the TPS386000 data sheet.

Precision affects every part of our lives – from ordering lunch meat at the deli to calibrating delicate lab equipment.

And a new high-precision operational amplifier – a circuit that magnifies tiny electric currents so that they can be measured and managed – offers an exceptional level of accuracy in industrial, automotive, medical, personal electronics, and test-and-measurement equipment.

“The performance on this device is so precise that it’s like measuring a dime on the Empire State Building,” said Richard Barthel, a systems engineer who worked on the team that developed the OPA388. “It takes something very small and gets it right on target.”

Operational amplifiers – or op amps – are links between sensors that measure analog signals such as pressure, temperature and flow and the digital brains behind technologies that are so integral to our everyday lives.

Sensors pick up analog signals from the environment around us that in many cases are measured in the millionths of a volt – too small to be useful for the circuits that convert them to digital signals. The job of op amps is to boost those signals to higher voltages that can then be measured, interpreted and managed by computers.

In that amplification process, any variation in the signal gets progressively more distorted as it works its way through the subsequent signal chain. That, in turn, affects the precision of the final measurements produced by a piece of equipment, said Ying Zhou, product marketing manager for the device.

Our zero-drift and zero-crossover technologies – which our newest op amp combines in one device for the first time – correct for any noise and errors in the signals and remove the need for designers to add discrete calibration circuits to the systems they create.

Combining these technologies will lead to improvements in the accuracy of measurements in applications ranging from electronic scales to heart-rate monitors and pressure sensors. For example, the device’s precision is beneficial for equipment such as:

• Gauges used in CT scan machines. This medical equipment requires a smooth and consistent movement so the weight and weight distribution of patients can be measured precisely, a critical factor in accurate diagnosis and treatment.
• Construction equipment. Contractors, civil engineers or other workers will be able to measure elevation and distance with pinpoint precision during building construction, which could increase structural integrity.
• Weigh scales. Achieve more precise weight measurements – whether you’re ordering a few slices of lunch meat at a deli or checking the weight of a fully loaded semi-truck.
• Medical lab equipment. Smaller equipment and more precise diagnoses could mean less time in the clinic and more accurate diagnoses for patients.

“Precision affects everybody,” Richard said. “The OPA388 takes very small measurements and gets them right on target with high accuracy and resolution. It threads the needle.”

If you are interested in learning more, read these TI Tech Notes regarding the features and benefits of zero-drift and zero-crossover technologies.

Industry 4.0 has revolutionized the manufacturing industry, changing how factories are designed and implemented. In factory automation and process-control applications, Industry 4.0’s impact comes down to two fundamental concepts: the proliferation of decentralized systems and smart deterministic systems. Decentralized systems inherently need to be modular and flexible. Efficient, low-power and thermally optimized designs are the key enablers for such systems. Smart deterministic systems are modules that can detect faults early and increase reliability.

In factory automation and process-control applications, Digital-to-Analog Converters (DACs) are most often found in analog outputs used for both programmable logic controllers (PLCs) and sensor transmitters. In both cases, the DAC can be used to deliver either a voltage output or current output.

The DAC8775 is TI’s newest high-precision DAC, that is the most integrated in the industry by including 4-20mA driver, voltage output and on chip adaptive power management. In this post, I’ll provide examples of design techniques as they relate to the DAC8775 and explore how you can design for the current trends in this industry.

Many system controllers handle hundreds of Input/Output (I/O) points due to the increased number of sensors. This poses a challenge for designers to fit more I/O channels into a small form factor, increasing the need for thermally optimized and highly efficient systems. Most analog output module 4-20mA driver circuits employ a high-side voltage-to-current conversion circuitry with a gain stage. Figure 1 shows a typical architecture.

The loop established by Amplifier A1 converts the DAC output voltage into a current. Through negative feedback, Amplifier A1 will set the voltage across R_SET to be equal to the DAC output. This voltage drop across R_SET will set the current flowing through the first stage, I_M. (I am assuming an ideal case where I_RSET is equal to I_M.) This generated current, I_M, is further gained up by the use of a loop established by the combination of Amplifier A2 and the R_MIRROR and R_SENSE resistor pairs. The amplifier A2 will force the voltage across R_SENSE to be equal to V_MIRROR .This generates a load current that is gained up from I_M by a factor proportional to the ratio of R_MIRROR and R_SENSE. R_LOAD, shown in Figure 1, usually represents a linear actuator load, as is the case with PLC systems. Since the current passing through R_MIRROR is not supplying the load, it will directly reduce the system’s efficiency. A good design practice is to minimize this current – setting it to less than 1% of the output current. For calculation purposes, let’s ignore I_M, assuming a high ratio (>1-to-100) between R_MIRROR and R_SENSE.

Figure 1: High-side voltage-to-current converter

In a typical case, the V_POS voltage can vary anywhere between 12-36V. R_LOAD can also vary from a short to 1kΩ. To illustrate the point, consider as our first example the case of V_POS equal to 36V and R_LOAD equal to 1Ω. When a valve is set to full scale, the controller will drive 20mA through the load. This means that the power consumed by the load is P_LOAD = I²R = 0.4mW.

The total power generated is P_generated = VI = 0.72W. From this example, it’s evident that the voltage-to-current conversion circuitry dissipates the rest of the power: 0.72W-0.4mW = 0.7196W. This is a highly inefficient system and will cause an unnecessary increase in system temperature.

Consider a second example where the load impedance is higher, at 1kΩ. In that case, P_LOAD = I²R = 0.4W. The total power generated is P_generated = VI = 0.72W. The voltage-to-current conversion circuitry dissipates the rest of the power: 0.72W-0.4W = 0.32W.

You can imagine that adding more channels in such a small space becomes unsustainable if there is a vast amount of power loss, which directly increases system temperature, reduces reliability and increases failures. The examples I’ve given show the power loss just for a single-channel design. In the case of four channels, the power losses in the first and second examples would be close to 2.8W and 1.2W, respectively.

Because power loss increases dramatically with the use of even higher channel count modules, one possible solution is to adaptively change the V_POS supply depending on the load. You can do this by adding a simple feedback network and employing a buck/boost converter to supply just the necessary power to the load. Such a system would look like the block diagram shown in Figure 2.

Figure 2: High-side voltage-to-current converter with a buck/boost converter

In this design technique a buck/boost converter will sense the drain-to-source voltage of the output FET driving the load and generate an internal proportional error current. Through a complex state machine algorithm the device will make a decision to buck or boost the supply. This technique is utilized in the quad Channel DAC8775 to achieve higher efficiency.

If you use the same values as the first example, when the load is 1Ω, the buck/boost converter would buck the supply to the DAC down so that it gets the minimum supply needed. In the case of the DAC8775, that would as low as 4.5V.

As in the first example, P_LOAD = I²R = 0.4mW. The total power generated is P_generated = VI = 0.09W. The voltage-to-current conversion circuitry dissipates the rest of the power: 0.09W-0.4mW = 89.6mW. Therefore, the power consumption is improved by a factor of eight when compared with example 1.

For the 1kΩ load case, P_LOAD = I²R = 0.4W. The total power generated is P_generated = VI = 0.46W, since the buck/boost converter will set V_POS to 23V. The voltage-to-current conversion circuitry dissipates the rest of the power: 0.46W-0.4W = 0.06W. Therefore, the power consumption is improved by a factor of five when compared to the design with no buck/boost converter feedback.

The DAC8775’s efficiency also results in a much more thermally optimized system. Comparing the junction temperature of the die in a four-channel design with and without adaptive power-feedback circuitry shows a significant improvement in die temperature. Figures 3 and 4 show measurement results for the DAC8775, comparing the die temperature with and without the use of a buck/boost converter for both 1Ω and 1kΩ R_LOAD cases. As you can see from Figure 3, this technique can improve the junction temperature by up to 36°C.

When squeezing more and more channels into a smaller space, thermal optimization becomes a critical performance parameter that differentiates module capability. In thermally unoptimized modules, system failures are common and performance degradation occurs due to large temperature drift. The DAC8775 addresses both of these challenges due to its high integration and high efficiency and achieves excellent DC and drift performance.

Figure 3: Die temperature for R_LOAD of 1Ω

Figure 4: Die temperature for R_LOAD of 1kΩ

In case the die temperature goes above 150°C, the DAC8775 offers an over-temperature alarm, part of an extensive set of smart diagnostic features that help detect faults early. These include open load, short circuit, cyclic redundancy check (CRC), watchdog timer and compliance voltage. In addition to fault alerts, the device allows you to choose pre-set actions that facilitate reliable system operation. You can tell the device to do nothing, shut down or go to a pre-programmed safe code.

TI’s wide portfolio of signal-chain offerings enables you to design modules that are efficient, thermally optimized and smarter. Learn more by checking out TI’s broad precision DAC portfolio or the DAC8775. 

Additional resources

• Download the DAC8775 datasheet.
• Evaluate the DAC8775 with the DAC8775 evaluation module.
• Download the reference design, “EMC/EMI tested Quad Channel Industrial Voltage and Current output driver reference design.”
• Download the reference design, “Less than 1W, Quad Channel Analog Output Module with adaptive power management reference design.”
• Learn more about TI’s precision data converter portfolio.
• Watch this video about the DAC8775 features and uses.

Demonstrating your Internet of Things (IoT) cloud application has never been easier! A new addition to the SimpleLink™ SensorTag family, our SimpleLink Wi-Fi® CC3200 SensorTag kit enables developers to connect to the cloud faster and easier than before. 

Available now, the SimpleLink Wi-Fi SensorTag kit leverages our low-power SimpleLink Wi-Fi CC3200 device, the industry’s first wireless microcontroller (MCU) to be Wi-Fi CERTIFIED™ at the chip level. This low-power technology enables the SensorTag to be powered only by AAA batteries and makes it an optimal demo platform for battery-operated applications.  

Our new Wi-Fi SensorTag kit has ready to use design files to speed up prototyping of your IoT application. Users can get started instantly without having to go through standard development board setup. With many out-of-the-box capabilities and a free iOS or Android™ app, there is no programming experience required to start using the SensorTag kit. Simply download the free mobile app to get started in minutes! 

(Please visit the site to view this video)

The Wi-Fi SensorTag kit can connect to any Wi-Fi network, no gateway needed, and was designed for easy provisioning and connection to the IBM Quickstart cloud.  

The SimpleLink Wi-Fi SensorTag kit has 10 integrated low-power MEMS sensors that enable developers to collect and store a wide range of data in the cloud. Supported sensors include ambient light, magnetic sensor, humidity, pressure, accelerometer, gyroscope, magnetometer, object temperature and ambient temperature. Learn more about these sensors here.

Order your SimpleLink Wi-Fi SensorTag kit today to get instantly connected to the cloud.

You can jumpstart the design of your IoT application with the SimpleLink Wi-Fi CC3200 LaunchPad development kit. This board can be directly connected to a PC with Code Composer Studio™ cloud integrated development environment (IDE) and IAR Embedded workbench. Visit dev.ti.com and get started today. 

Reviewing this year’s program of events for APEC in Tampa, Florida, on March 26-30 provoked a few nostalgic memories. Back in 1994, I attended my first APEC conference at Disney World in Orlando, Florida, and was impressed to see so many power electronics experts at one event. I actually had the pleasure to meet Ned Mohan, the author of my undergraduate power electronics textbook. Unfortunately, I hadn’t brought it along for an autograph.

That event, as in the previous years, had many papers and speakers discussing the latest innovations in power-supply design, including soft switching inverters, which helped me with my graduate research. To interact with the authors of the papers I studied and to listen to their presentations was a learning experience that I will never forget.

I also enjoyed the product demonstrations and discussions with other engineers at the exhibitor booths. In graduate school, I had only read about the specifications of “hockey puck” diodes and insulated gate bipolar transistor (IGBT) half bridges. Seeing the products and asking questions was also very beneficial for my research project.

From educational seminars to live in-booth demos, APEC’s tradition of expanding your knowledge of power electronics continues at this year’s show. Stop by TI’s booth, No. 701, to get your questions answered by TI experts; meet Bob Mammano and enter for a chance to win a copy of his new book, “Fundamentals of Power Supply Design” (Figure 1); get to see our newest products; and witness the unveiling of end-to-end power-management system solutions including hardware, software and reference designs that help you get to market quickly.

Figure 1: Bob Mammano’s book, “Fundamentals of Power Supply Design”

If you are a returning attendee or this is your first time at the show, I hope you enjoy the conference as much as I have. Perhaps Bob Mammano will agree to autograph a couple of Power Supply Design Seminar books that I cherish – if I remember to bring them along.

What you’ll find in TI’s booth

At APEC, TI will give designers the power to:

• Innovate:
  • See how the industry’s first end-to-end gallium nitride (GaN) solution revolutionizes data center AC-to-processor power density by over 3x, with TI’s GaN technology clocking in at over 6 million device reliability hours.
  • Experience the design simplicity that power modules provide as TI takes the wraps off its new high-current PMBus module with telemetry for communications applications (Figure 2). 
  • Watch two new low quiescent current (I_Q) step-down DC/DC converters power the next evolution of automotive USB Type-C™ and industrial heating, ventilation and air conditioning (HVAC) applications.
  • See the industry’s first multiphase bidirectional current controller efficiently transfer power between 48-V and 12-V automotive dual-battery systems.

    Figure 2: High current PMBus power module with telemetry for communication applications

• Design:
  • Analyze and interpret designs with new 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.
  • Check out the new TI Power Management Lab Kit (TI-PMLK) buck-boost board (Figure 3) 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.

Figure 3: TI-PMLK buck-boost board

• Learn:
  • Attend the APEC plenary “Power Semiconductor Technology – Flexibility for Tomorrow’s Solutions” by Ahmad Bahai, Texas Instruments chief technologist and senior vice president, from 1:30 to 2 p.m. Monday, March 27. Bahai will show how the demand for smart, high-efficiency power management is outpacing the average growth rate of the semiconductor industry.
  • Join TI power experts at more than 30 technical sessions covering topics such as renewable energy systems, wireless technology and GaN device reliability validation.
  • Meet Bob Mammano daily in the TI booth, author of “Fundamentals of Power Supply Design,” your new indispensable reference book for all things power. Enter for a chance to win an exclusive autographed pre-release copy.
  • Grab TI’s new month-to-month power-topology guide in the TI booth while they last.

Stay connected with TI at APEC 2017: see ti.com/apec2017 and follow us on Twitter and Facebook. Tune into Facebook Live discussions throughout APEC to watch demonstrations, hear more about TI’s latest news in power innovation, and get your questions answered by TI experts in real time.

Find out more about TI’s power-management portfolio

• Follow TI’s Power House blog for tips and tricks on power-supply design.
• Find the best TI power-management product for your next design.

MSP430™ microcontrollers (MCUs) are at the heart of many embedded applications being discussed at embedded world 2017 in Nuremberg, Germany this week. This is especially true for sensing and measurement applications including smoke detectors, thermostats, and metering devices as well as capacitive touch-enabled products such as smart electronic locks and keypads, remote controls, security panels, and human machine interfaces (HMIs) in the factory, building or home.

If you are attending the embedded world this week, be sure to stop by the Texas Instruments booth located in Hall 3A / 3A-420.  We are showcasing a lot of different products including several from our value line sensing MCUs such as the MSP430FR4133 MCU and MSP430FR2311 MCU LaunchPad™ development kits. We will be demonstrating how these cost-optimized MSP430 MCUs can be used in applications such as basic thermostats (as shown below) and smoke detectors. 

Figure 1: Example of thermostat implementation with FRAM MCUs reference design

Also on display will be several demos based on the new high-performance MSP430FR5994 device. This is the first MSP430 MCU to include our unique energy-efficient low energy accelerator (LEA), which is a highly optimized peripheral for complex algorithm processing. These demos will include a reference design showing the LEA module’s filtering and signal processing, a demo of our wireless boot loader application report which is great for updating firmware over the air in hard to reach locations in factories, grid infrastructure and buildings, and a very cool, high accuracy ultrasonic measurement system also based around the MSP430FR5994 LaunchPad kit.

Figure 2: Filtering and signal processing reference design

And last but not least, we will have several of our MSP430 MCUs with CapTIvate™ touch technology demos on display including a new reference design for a Bluetooth®-enabled smart eLock or access panel. Our high performance capacitive touch solution helps to solve many of the challenges faced when adding capacitive sensing to your design, such as conducted noise immunity, moisture rejection and the ability to work with a wide range of overlay material and thickness. CapTIvate technology can even enable  grip detection to turn on or provide safety controls in handheld equipment, slick metal-touch capacitive buttons for appliances and human HMIs, very small (3mm x 5mm) capacitive sensors  and capacitive sensing through thick glass enclosures. Offering unrivaled noise immunity and ultra-low power operation, CapTIvate technology can give your next generation project the best user experience possible.

Figure 3: CapTIvate technology access control panel

Be sure to stop by to check out all the TI demos this week in Nuremberg.

Additional resources:

• Learn more about ultra-low-power MSP430 FRAM MCUs.
• Need a value line sensing MCU? Check out the MSP430FR211x family.
• Read more about CapTIvate technology:
  • “Rain on this touch panel parade won’t matter”
  • “Need a hand with messy jobs? TI’s CapTIvate technology can help."

Proven effective through many years of use in proprietary networks, bands within the Sub-1 GHz frequency enable long-range communication for applications such as connected door or window sensors, smoke alarms and metering. In addition to long-range, these radio waves can better penetrate walls and bend around obstacles while consuming very little power for operation.

These attributes make Sub-1 GHz an optimal choice for Internet of Things (IoT) applications that connect sensors to IoT platforms. However, when connecting a system of smart nodes to the cloud, Sub-1 GHz technologies have historically been hindered by a lack of standard networking solutions within this spectrum. As a result, companies typically require staff with low-level RF communication expertise to implement their own connectivity stacks, and, in turn, transfer data from these accessible IP networks to downstream services.

To streamline this process, TI developed the TI 15.4-Stack software, an 802.15.4g communications stack for Sub-1 GHz, along with Linux-based gateway software running on the Sitara™ AM3358 processor that powers the BeagleBone Black. In addition, TI has taken it a step further by collaborating with stackArmor to develop a cloud-based Software-as-a-Service (SaaS) solution to help engineers connect their applications to the cloud. As an Amazon Web Services (AWS) consulting partner, stackArmor provides cloud migration and support services, and maintains a dedicated IoT cloud solutions practice.

The below example outlines how to move sensor data arriving at a Sub-1 GHz communication stack to the AWS cloud for storage, display and analysis.

AWS Application Overview

AWS is a fully managed cloud service that includes both specific AWS SaaS applications and general cloud computation functionality. Figure 1 works to outline how stackArmor’s application uses two SaaS solutions (AWS IoT’s Rules Engine and DynamoDB) to transfer data received by the Sub-1 GHz gateway to the cloud. For this example, the referenced device is a BeagleBone Black-based gateway.

To visualize the data for this application, a popular opensource platform, Angular.js, was used to create a dashboard powered by EC2 – another AWS service that enables server instances to run non-AWS software. EC2 was also used to run the NGINX security proxy for malware protection along with other ancillary services.

FIGURE 1: StackArmor AWS Application

As shown in Figure 1 above, the AWS IoT service first establishes communication between a device and the cloud. However, for the AWS IoT server to receive messages, two things must be installed – a software development kit (SDK) and a security certificate (both are provided by AWS).

The AWS SDK is available in various languages, including C and Node.js (JavaScript), but assumes the underlying hardware supports a TCP/IP stack. For this reason, it cannot be run directly on non-IP nodes such as those running BLE or Sub-1 GHz. We chose the Node.js SDK for our development.

Additionally, the SDK provides necessary commands for connecting and sending as well as receiving MQTT messages from the AWS IoT cloud service. This functionality is perfect for our application as it requires bi-directional transmission of sensor data from the device to the cloud, along with actuation signals that change the state of the device or sensors through the web application.

The associated security certificate must also be installed to ensure that only authorized devices can connect to the cloud.

To function properly, the AWS IoT service also requires setup and configuration of a cloud representation of our BeagleBone Black-based gateway, which allows messages sent from the physical gateway through the AWS service to be published on this digital representation of the gateway. And as AWS IoT uses MQTT, we created corresponding topics to represent the actual end-node sensors and actuators located on the SimpleLink™ CC1350 LaunchPad™.

Connected to the “digital gateway” are AWS IoT’s Rules Engine and a DynamoDB (NoSQL) database that stores messages received from the physical device. Rules Engine is used to determine where these messages are stored, while DynamoDB actually stores the messages in either a network-specific or end-node file.

To make the file determination, Rules Engine reviews the topic associated with each message and then sorts it to the appropriate file. Unlike embedded applications that require specific actions to be coded, many AWS actions can simply be specified by configuration. For example, you can configure AWS IoT to send an SMS message or email when a specific message arrives. Because we chose Rules Engine and DynamoDB for this application, the set-up did not involve any coding.

As previously mentioned, the IoT dashboard was developed with Angular.js, which periodically sends queries to the DynamoDB database for new data. This data is then displayed on the dashboard using easy-to-read charts and graphs. This web-based application can also transmit actuation signals from the dashboard to the gateway, through the AWS cloud connection, to toggle network power or manipulate the gateway sensors.

To learn more about this implementation, including in-depth documentation of the hardware set-up and communications stack, you can check out the TI reference design or download the Sensor to cloud reference design to get started.

You may also order kits here:

• SimpleLink CC1350 LaunchPad™ development kit
• BeagleBone Black

Guitars, drums, cymbals … the 2017 National Association of Music Merchants (NAMM) Show had it all, but what seemed to be making the most noise was the professional audio gear.

I’ve heard a lot about the NAMM Show, the largest music gear conference in the U.S. (probably the world), and my excitement attending for the first time was hard to contain.  The music world from musicians, to mastering and mixing engineers, all come together to see the latest instruments and equipment the industry has to offer. 

Of course, the major guitar and professional audio equipment manufacturers you would expect at this show had the largest booths, but that didn’t keep other exhibitors from showing some cool equipment as well.

For us at Texas Instruments, this was our first year exhibiting at NAMM, although it was hardly our first year designing audio components (audio amplifiers and digital-to-analog converters) for the professional audio and music industry. For 2017, we had a lot to show around our new family of fully integrated high-performance Class-D amplifiers. Here is our booth the night before the show, ready with multiple demos showcasing our new Class-D amplifier family (Figure 1).

Figure 1: Texas Instruments’ booth at the 2017 NAMM Show

Walking through the guitars was great, but I was really there to see the latest with speakers and amplifiers. Everyone was offering speakers with more power and more integration. Below is a short list of some of the cool products exhibitors showed at NAMM:

• A new Class-D guitar amp with the same sound and style you would expect, but at about half the size. It also had a cool Bluetooth® app for controlling the sound tone and character.
• A new connected PA speaker system that recalled instrument settings, speaker levels and EQs through a smartphone app. The speaker they used was from their PRX800-powered loudspeaker lineup.
• Studio monitors were in full force, with multiple manufacturers offering products with amazing performance using the latest Class-D technology.

What continued to be a trend in the professional audio space were speakers designed with audio amplifiers inside. I heard from numerous speaker designers that it’s easier to match an amplifier and speaker during the design phase, and it’s also easier for sound engineers to use.

I received similar feedback about TI’s Class-D amplifiers. We had a variety of demos including powered speakers, a guitar amplifier and a Dolby Atmos sound bar that all used our new TPA3255 family of integrated high-power amplifiers. After about the third day, I had heard many people stop by our booth and mention that they had never considered a fully integrated chip solution. Most designers today use audio amplifier modules, which are pre-built printed circuit boards (PCBs) with discrete component amplifiers. Yet there are many benefits to using an integrated chip instead, including:

• Protection. An integrated chip offers the same level of protection as amplifier modules, with overcurrent, thermal and short-circuit protection.
• Ease of design. The integrated option is easy to add to your existing pre-amplifier board. Simply add the amplifier chip, output filter, and a few components for settings and control.
• Size. The integrated solution can offer a reduction in size because the protection, audio-loop circuitry and auxiliary power rails are all built right into the device.  See the solution size in Figure 2.
• Reliability. There are only a few components on the board, which decreases the failure rate. In addition, the chip is backed by TI’s long history of integrated circuit design and testing standards.
• Thermal. As with any Class-D, you get the benefit of improved efficiency and reduced heat-sink size. An additional benefit of an integrated solution is that you only have one device that you need to heat sink, so system design and mass production assembly become easier as well.
• Component selection. With an integrated chip, you have the flexibility to choose the best-quality or best-value components like capacitors and inductors to optimize for your system goals.

Figure 2: TPA3255 600W Class-D audio amplifier

With TI’s new family of Class-D audio amplifiers, you can get even more out of your amplifier:

• Power levels as high as 600W.
• Better audio dynamics, with a dynamic range >111dB.
• Audio performance as good as or better than a Class-AB amplifier, with total harmonic distortion plus noise (THD+N) below 0.01% all the way to clipping.
• Design flexibility to add external tuning and feedback circuits, allowing you to tune the device to your signature sound.
• The new family’s five pin-compatible power levels mean that you can use the same design for all of your speaker power levels but use different power-level chips.

To be honest, it was difficult to hear much by the end of the show. We even measured the exhibition hall’s noise level at around 80dB – just short of standing next to a blender for eight hours each day. However, I would encourage everyone to have a listen to the TPA3255 series of Class-D amplifiers. Let us know how it sounds and if it would fit well in your application.

Additional resources

• Start designing quickly with the TPA3255 evaluation module (EVM).
• To help select the right external components for your system, download the Device Setup Guide & Configuration Tool for the TPA3251, TPA3255 and TPA3245 devices. Select your output configuration and parameters and use the suggested values as a guideline for development.
• Calculate and design audio Class-D LC filters in minutes using the Class-D LC Filter Designer.
• Read these application notes from our audio experts:
  • LC Filter Design
  • Post-Filter Feedback
  • Analog Input Grounding for Single Ended Inputs
• To learn more about high-power Ultra-HD Class-D audio amplifiers, visit TI.com/highpoweraudio.

As the world becomes more connected, embedded systems continue to add new connectivity options, along with advanced sensing capabilities and local analytics. And a rapidly expanding list of functionalities drives the need for new protocol stacks, sophisticated algorithms and comprehensive software frameworks to schedule and manage system complexity.

Even software development is facing the pressures of shrinking timelines and a constant need to adapt products for different markets – all while incorporating a variety of connectivity standards or meeting other requirements. For embedded projects, these obstacles often also include fragmented hardware platforms, software incompatibility and different connectivity standards. But while companies continue to invest heavily in software engineering resources, the process remains a lengthy and challenging cycle.

To help solve these issues, TI announced the release of its new SimpleLink™ MCU platform. Created for developers, this platform brings together the industry’s broadest portfolio of connected hardware, a unified software solution and immersive resources within one environment. This approach will ultimately expedite development time and help future-proof product designs.

Broadest portfolio of 32-bit ARM-based microcontrollers (MCU)

To be successful in different markets, all with constantly evolving requirements, it is critical to design within a platform that can scale across multiple connectivity standards and quickly adapt to a base product. The SimpleLink MCU portfolio of devices offers a broad range of wired and wireless MCUs that all share industry-leading features important to connected applications: ultra-low power, robustness, advanced security and analog integration, and support for a wide range of differentiated wired and wireless protocols.

Built on a common foundation, each device within the SimpleLink MCU portfolio integrates a number of features such as acquiring and processing high-precision analog signals, fortifying systems with more security, increasing long-range communication or squeezing several more years of life out of a coin cell in a sensor node. The devices can be classified into three categories, as illustrated in Figure 1:

• MSP432™ host microcontrollers offer advanced analog capabilities and a wide range of memory scalability to run multiple wireless protocols – typically used to drive wireless network processors.
• Wireless microcontrollers include full system-on-chip (SoC) solutions that incorporate a wireless network processor with a microcontroller, covering a wide range of wireless connectivity and standards that include: Wi-Fi®, Bluetooth® low energy, Sub-1 GHz and dual-band (Sub-1 GHz and 2.4GHz).
• Wireless network processors offer an integrated radio and network processor to run the network stack, connecting to a host microcontroller to run the top-level application.

Figure 1: SimpleLink microcontrollers supported by one software platform

SimpleLink MCU SDK

TI developed SimpleLink MCUs around a single software foundation. The SimpleLink software development kits (SDKs) are based on common drivers, frameworks and libraries that ensure 100 percent code compatibility across the platform. This device-agnostic approach provides easy portability of application code across SimpleLink devices now and in the future. Platform-level software portability allows you to invest in software development once and reuse it across multiple products and applications.

(Please visit the site to view this video)

With the SimpleLink SDK, you can use TI Drivers and functional APIs to gain access to portable and intuitive peripheral drivers, or opt to peel back into the hardware abstraction layer (HAL) for greater control of your applications with low-level optimization. The integrated TI-real-time operating system (RTOS) kernel helps solve the scheduling of multiple tasks or sophisticated algorithms in real time, while Portable Operating System Interface (POSIX)-compliant application programming interfaces (APIs) open the door for working with third-party OS/kernels and software components. A wide range of SDK plug-ins help you attach additional connectivity and external functionalities to your SimpleLink application.

Figure 2: TI’s unified tool chain, training and resources deliver accelerated development path, from entry to production

TI’s SimpleLink platform offers simple, powerful hardware and software tools that enable you to ramp up quickly based on customer needs. From evaluating the SDK and demos with TI’s cloud-enabled repository, TI Resource Explorer, to digging deep into SimpleLink MCU development with SimpleLink Academy’s curated and interactive trainings, you can become an expert and hit the ground running when your SimpleLink LaunchPad™ development kit arrives.

Code Composer Studio™ software also delivers a feature-rich development environment for the SimpleLink devices with advanced debugging capabilities. And you have the option to use a number of third-party integrated development environments (IDEs) or tools such as IAR Embedded Workbench or Segger.

Additionally, many configuration and advanced debugging tools simplify your development and debugging experience.  The breadth of the SimpleLink platform is illustrated in figure 3 including silicon, development kits, training, tools and software. 

Figure 3: One platform. Unlimited potential

In short, TI’s SimpleLink MCU platform offers a comprehensive, unified software and hardware solution to help you tackle tough challenges for embedded products.

To dive deeper into all platform offerings, be sure to check out our resources below.

Additional resources:

• Get started with the SimpleLink MCU platform: www.ti.com/simplelink
• Read more about the SimpleLink SDK and tool ecosystem in these new white papers:
  • “Simplifying software development to maximize return on investment”
  • “Deep dive into the tools and development kits of the SimpleLink™ MCU platform”

• See how the SimpleLink platform can help address building automation systems:
  • "Connected microcontrollers essential to automation in buildings"

Finding the library you want is now easier than ever thanks to TI’s new Accelerated Libraries page. From this one page you can access TI’s popular signal processing, imaging, linear algebra and OpenCV libraries, as well as free video codecs for the C66x and the IVA-HD subsystem found on Sitara™ AM57x processors. Each library has its own page with a description and links to download the software.

Available accelerated libraries:

• Signal Processing Libraries: Otherwise known as MATHLIB and DSPLIB, these libraries contain optimized math and DSP routines including trigonometric and hyperbolic functions, FFTs and matrix operations.
• Image Processing Libraries: Optimized function libraries for image analysis, filtering, format conversion, compression and decompression.
• Linear Algebra Libraries: Includes BLAS and LAPACK for dense linear algebra
• OpenCV Libraries: Version 3.1 of the popular open source computer vision library
• C66x video codecs: Free encoders and decoders including H.264, H.265, JPEG2k, MPEG2 and MPEG4.
• AM57x video codecs: Free codecs that run on the IVA-HD subsystem without placing any load on the ARM or DSP cores. Codecs include H.264 and MPEG4.

Utilizing these libraries is an easy way to improve performance and shorten development time. These libraries provide algorithms, functions and routines commonly used on TI’s embedded processors across a wide variety of applications.

Many of the libraries have been highly optimized for our processing architecture, providing substantial performance increases over running typical C code. With easy to use APIs and plenty of examples, the libraries are easy to integrate into your code. There is even drop-in compatibility to replace industry standard libraries such as FFTW and OpenCV.

Customers have gone to production utilizing the C66x and AM57x video codecs, saving them the time of having to develop it themselves or the cost of purchasing it from a vendor. The signal processing libraries have long been utilized by DSP developers to improve their performance by utilizing the optimized core routines, like FFTs and IIR filters that are the building blocks of so many DSP applications.

 We hope you find these useful for your application. Let us know which functions have been valuable to you and what other functions/libraries you’d like to see.

Picture the connected factory of the future. The factory floor hums with activity – motors spinning, robotic arms shifting about, equipment humming and vibrating with electricity. Everything the eye can see – and more – is connected electronically. This is the vision of the industrial Internet of Things (IIoT).

A multitude of data is being continually relayed from each machine to a remote server in the cloud and back – conveying a digital “mirror image” of each piece of equipment and its status – from the vibrations and noise produced to the temperature and humidity emitted. In the cloud, data analytics are applied to capture each machine’s “normal state” – and alert operators remotely if anything out of the ordinary occurs.

The connectivity needed to link the equipment in the industrial Internet of Things and relay information to the cloud could include Sub-1 GHz, Wi-Fi® network(s), and/or a local Bluetooth® low energy connection to help operators locate equipment in the factory using beacons, then connect directly to configure and service or operate the equipment.

“A system deploying all of these ‘connectivity standards’ would require three wireless technologies on top of any wired connections,” said Systems Engineer Roger Monk. “In the past, this would have required the engineers to develop three separate products, use three sets of tools, manage many sets of software dependencies, and climb a big learning curve.”

Moreover, they might have to go through the same process all over again if a new connectivity standard emerges later. It could slow or delay the pace of innovation for the IIoT.

But with our new SimpleLink™ microcontroller (MCU) platform– available now – the whole system can be built with one product family and easily configured for the required connectivity technology with a common software update mechanism, peripheral drivers and development environment.

The platform allows developers to use simple plug-ins to reuse 100 percent of the code already developed whenever the connectivity needs of an end product evolve. It is also possible to add another connectivity standard later with an additional plug-in. Watch this short video to see how it works. 

(Please visit the site to view this video)

“I see this platform as a game-changer,” said Ajinder Singh, general manager of building automation.

“From the development cycle that can now be shortened, to improving the ease of maintaining software, developers of industrial designs will see a lot of efficiencies."

Moreover, for a lot of our industrial customers, understanding and enabling products such as garage door opener or sprinkler systems across different connectivity standards is relatively a new journey that requires resources and additional skillset. SimpleLink offers an efficient, and highly scalable and sustainable platform that will make it easier for developers to adopt future connectivity standards into their products, thus shortening their development cycle.

The platform allows developers to use existing and future products across our Connected MCU portfolio – along with a cohesive software platform and a common set of tools.

The SimpleLink MCU platform is designed to protect developers’ software investments for equipment they are building today and in the future.

“For our customers, this solves the biggest challenge that engineers face when designing with connected microcontrollers. Adapting to a new connectivity standard previously meant starting the most time consuming and costly portion of the design – software – over. With SimpleLink MCU, that is no longer the case,” said Ray Upton, vice president and general manager of Connected MCU.

Innovators can now have more agile development cycles, spend less on development, get to market faster and expand their product offering more quickly. In this fast-growing market, the standards change rapidly, and this platform now offers unparalleled flexibility.

Often during early development stages, the processing performance, peripheral interfaces and wireless connectivity options needed for an application aren’t known until a significant proportion of the development work has been done, or until field trials and user feedback is received.

“With this platform, developers can start out quickly building first versions of their products on a solid base platform for testing, knowing that they will be able to easily innovate or differentiate, changing components as necessary without having to re-invest in software development for the new features,” Roger said. “Being able to adapt and push those decisions later in the product development has huge benefits for customers.”

Developers can use our cloud-based resource, dev.ti.com, to browse and rebuild example applications on the cloud server, then create application-specific projects to run on real hardware. We also offer an expanding online “SimpleLink Academy” with step-by-step guides targeted toward specific components.

“We’ve had customers quickly evaluate performance of algorithms or even cloud protocols using these tools without spending any time installing custom tools locally. They’ve even been able to share those ‘cloud’ projects with worldwide development teams,” said Roger.

From our SimpleLink MSP432™ MCUs to our Wi-Fi products, our SimpleLink portfolio streamlines our development platforms and makes it easier for our innovators to work across these platforms.

“We think about platforms in terms of new silicon and new features, but really when we step back and look at the problems we’re trying to solve, we’ve found that protecting our customers’ software investment is key,” said Ray.

The SimpleLink MCU platform is available today, recently launched at Embedded World.

To learn more about the platform, here are two related white papers:

• SimpleLink Whitepaper
• Building Automation Whitepaper

One of the things I love about my job as an applications engineer is pretending that I’m a TI customer. I spend my days dreaming of all the possible ways customers use solenoids, design solenoids and drive solenoids. Today, I’m considering what concerns TI customers might have regarding voltage supply and solenoid or relay selection.

One customer I can imagine is a valve designer – maybe pneumatics in factory automation or media valves for process automation. Most factory- and process-automation equipment is designed for 24V supplies. However, customers may have control signals for a wide range of AC or DC voltages – 12 V, 24 V, 36 V, 48V, or even 120 or 240 V for some valves and contactors. To accommodate all of these voltages, I would need to design five different coils and have five separate products.

One solution could be to design one coil for 12V, then use a resistor to limit the current into the solenoid for each voltage option. However, this wastes energy and could dissipate a lot of heat from the resistor, especially if the 12-V coil is used for the 220V design.

Another, more energy-efficient solution is to use pulse-width modulation (PWM) driving and a freewheeling diode to regulate the current in the solenoid. Additionally, you could add current-sense feedback with PWM and control the current in the solenoid. The magnetic force produced by the solenoid to open or close a valve depends on the current flowing through the solenoid coil. The solenoid resistance increases with temperature. With an applied voltage, the increase in resistance will reduce the current in the solenoid, which reduces the magnetic force. At high temperatures, it is possible for the solenoid to de-actuate or for a relay to open its contacts if the current decreases too much. With current control, the solenoid current is always regulated to the required value independent of temperature, which makes the system more reliable and robust over temperature. You could implement current-sense feedback with a microcontroller and discrete signal-chain components, or with an integrated solenoid driver like the DRV110 (Figure 2) and DRV120 (Figure 1).

Figure 1: The DRV120 driving a relay using current control

Figure 2 shows how you can configure the DRV110 solenoid to accommodate AC voltages that energize solenoid valves or contactors. By using DC to drive the contactor instead of AC, you can simplify the design of the magnetics by eliminating the need for a shaded ring in the core.

Figure 2:  DRV110 used to drive the coil for an AC contactor

With this current-control technique, you can potentially design only one 12-V coil for the force requirements of the AC or DC 12-V to 48-V valves and the AC 120-V to 220V valves. This allows you to have multiple product offerings for valves while only needing to design one coil.

Another customer situation I can imagine is wanting to use a particular relay in a design, but the only supply rail available is too high. Let’s say that the relay is rated for 12 V, but the supply rail is 24V. One solution may be to just switch to a 24V relay for the system. While it sounds easy, perhaps that involves adding the new part number as an approved component. Maybe you can’t do this because it is a difficult or lengthy process, and you want to take your product to market quickly. You might also run into the same situation with a solenoid. Perhaps you really like the force of a particular solenoid, but it’s rated for 12 V when you have a 24-V rail.

Using current control can also solve this dilemma. You can use your 12V relay or solenoid for both 12-V and 24-V systems. Maybe the next-generation product will only have a 36-V supply rail. Even in that case, current control will allow you to continue using your chosen solenoid or relay. Perhaps by using the same solenoid in all three systems, you can get a volume discount from the solenoid/relay manufacturer for purchasing large volumes of that particular part number.

With current feedback, I solved my imaginary customers’ issues for voltage supply rail and solenoid/relay design or part-number selection. Is my imagination accurate to your design experience? Please share your experience in the comments or share any other great solenoid- or relay-driving solutions.

Additional resources

• Explore a 230V_ACsolenoid reference design that illustrates how to integrate current control.
• Check out another reference design that provides a solution to control solenoid current using a PWM-based controller.
• Learn how a PWM controller can save power in your solenoid.

The quintessential characteristic of a low-dropout (LDO) linear voltage regulator has to be dropout. After all, that is the source of its name and acronym.

At the most basic level, dropout describes the minimum delta between V_IN and V_OUT required for proper regulation. However, it quickly becomes more nuanced when you incorporate variables. Dropout, as you’ll see, is essential to obtaining efficient operation and generating voltage rails with limited headroom.

What is dropout?

Dropout voltage, V_DO, refers to the minimum voltage differential that the input voltage, V_IN, must maintain above the desired output voltage, V_OUT(nom), for proper regulation. See Equation 1:

                (1)

Should V_IN fall below this value, the linear regulator will enter dropout operation and no longer regulate the desired output voltage. In this case, the output voltage, V_OUT(dropout), will track V_IN minus the dropout voltage (Equation 2):

     (2)

As an example, consider an LDO like the TPS799 regulating 3.3V. When sourcing 200mA, the TPS799’s maximum dropout voltage is specified at 175mV. As long as the input voltage is 3.475V or greater, regulation is not affected. However, dropping the input voltage to 3.375V will cause the LDO to enter dropout operation and cease regulation, as shown in Figure 1.

Figure 1: The TPS799 operating in dropout

Although it’s supposed to regulate 3.3V, the TPS799 does not have the headroom required to maintain regulation. As a result, the output voltage begins to track the input voltage.

What determines dropout?

The architecture of the LDO primarily determines dropout. To see why, let’s look at PMOS and NMOS LDOs and compare their operation.

PMOS LDO

Figure 2 shows a PMOS LDO architecture. In order to regulate the desired output voltage, the feedback loop controls the drain-to-source resistance, or R_DS. As V_IN approaches V_OUT(nom), the error amplifier will drive the gate-to-source voltage, or V_GS, more negative in order to lower R_DS and maintain regulation.

Figure 2: A PMOS LDO

At a certain point, however, the error-amplifier output will saturate at ground and cannot drive V_GS more negative. R_DS has reached its minimum value. Multiplying this R_DS value against the output current, or I_OUT, will yield the dropout voltage.

Bear in mind that the more negative the value of V_GS, the lower R_DS achieved. By increasing the input voltage, you can achieve a more negative V_GS. Therefore, PMOS architectures will have lower dropout at higher output voltages. Figure 3 illustrates this behavior.

Figure 3: Dropout voltage vs. input voltage for the TPS799

As shown in Figure 3, the TPS799 has a lower dropout voltage as the input voltage (and output voltage, for that matter) increases. That is because a higher input voltage yields a more negative V_GS.

NMOS LDO

In the case of an NMOS architecture, as shown in Figure 4, the feedback loop still controls R_DS. As V_IN approaches V_OUT(nom), however, the error amplifier will increase V_GS in order to lower the R_DS and maintain regulation.

Figure 4: An NMOS LDO

At a certain point, V_GS cannot increase any more, since the error-amplifier output will saturate at the supply voltage, or V_IN. When this condition is met, R_DS is at its minimum value. Multiplying this value against the output current, or I_OUT, derives the dropout voltage.

This presents a problem though, because as V_IN approaches V_OUT(nom), V_GS will also decrease, since the error-amplifier output saturates at V_IN. This prevents ultra-low dropout.

Biasing the LDO

Many NMOS LDOs employ an auxiliary rail known as a bias voltage, or V_BIAS, as shown in Figure 5.

Figure 5: An NMOS LDO with a bias rail

This rail serves as the positive supply rail for the error amplifier and allows its output to swing all the way up to V_BIAS, which is higher than V_IN. This type of configuration enables the LDO to maintain a high V_GS, and therefore achieve ultra-low dropout at low output voltages.

Sometimes an auxiliary rail is not available but low dropout at a low output voltage is still desired. In such a situation, an internal charge pump can be substituted in place of V_BIAS, as shown in Figure 6.

Figure 6: An NMOS LDO with an internal charge pump

The charge pump will boost V_IN so that the error amplifier may generate a larger V_GS value despite the lack of an external V_BIAS rail.

Other variables

In addition to architecture, dropout is also affected by a few other variables, as outlined in Table 1.

Table 1: Variables affecting dropout

It’s clear that dropout is not a static value. Rather than just complicating your LDO choice, though, these variables should help you choose the optimal LDO for your specific set of conditions. Learn more about LDO dropout in the application note, Understanding LDO Dropout.

Additional resources:

• Read more LDO blogs.