To combat ever-stringent power requirements from the industrial and automotive industries, multiphase designs are a popular choice for engineers these days. For current requirements over 25A, more designers are opting for multi-phase approaches because of the key benefits they provide. Multiple phases provide lower output-ripple voltages when compared to single-phase designs, as well as better transient performances and better thermal performance, leading to higher efficiencies overall.

To achieve these key benefits in a synchronous buck converter, designers must interleave the phases. Although many integrated circuits (ICs) exist that interleave dual phases, the challenge arises when more than two phases are required. In this PMP10979 reference design, two dual-phase synchronous buck controllers, are connected in parallel to achieve a four phase design. Figures 1 and 2 showcase how the PMP10979 is capable of providing 13.5V at 95A (1282W) with an input voltage of 24V.

Figure 1: Phases 1 and 2 of PMP10979

Figure 2: Phase 3 and 4 and PMP10979

In order to maximize the benefits of this four-phase design (decreasing input/output ripple current, leading to a decrease in the stress on the inductor/field effect transistor [FET]), you need to run the phases 90 degrees apart. The internal oscillator of the LM5119 buck controller ensures that every dual- phase design runs 180 degrees out of phase. To ensure a 90-degree phase shift between the four phases, a synchronous external clock signal must be provided to both ICs. This can be achieved easily by using a 555 timer and inverter, as shown in Figure 3. The timer will output a square wave with a 50% duty cycle at twice the switching frequency of one of the LM5119 controllers, as well as an inverter. The output of the inverter will be routed to the other IC.

Figure 3: External clock circuitry for 90-degree phase shifting

This ensures that with every rising edge of the square wave, an IC triggers a switching cycle resulting in a phase sequence of phase 1, phase 3, phase 2, and phase 4, all shifted by 90 degrees. If you adjust the input voltage of the design to produce a 50% duty cycle, the 90-degree phase shift becomes apparent, as Figure 4 shows.

Figure 4: Switch node waveforms for 4 phases showing 90 degree phase shifting

Keeping the switching frequency for each phase lower than 200 kHz will ensure that switching losses are minimized in the high-side FET. Also, splitting the current into four phases reduces conduction losses in the low-side FET. Thermal performance is further improved because the total dissipation of power is now shared among many smaller components, as highlighted in figure 5.

Figure 5: Thermal performance at 1,280W output (PMP10979)

For more Power Tips like these, visit our Power Tips blog series: 

In a recent post about functional safety, ‘Better safe than sorry: The role of functional safety in our daily lives,’ the author presents a case for how functional safety is becoming critical for a variety of systems that touch our daily lives. From the cars we drive, to the elevators we ride, to the medical equipment we use, industry standards set functional safety requirements to minimize the risk from these systems.

System developers put in  a lot of effort to design, develop and certify end systems requiring functional safety. To ease the development of functional safety systems complying with ISO 26262 and IEC 61508 standards, Hercules™ microcontrollers (MCUs) offer hardware-integrated diagnostic features, along with supporting software and tools.

To further ease development with Hercules MCUs and make the functional safety-related features more accessible to a wider community of developers, today TI launched a new low-cost LaunchPad development kit. The kit expands TI’s LaunchPad ecosystem by adding two new tools for applications that rely on high performance.

Each LaunchPad is designed with our highest performance MCU yet, running dual ARM® Cortex®-R5F cached central processing units (CPUs) in lockstep at up to 330 MHz. The Launchpad also carries TI’s Precision PHYTER DP83630 Ethernet PHY, providing real-time synchronization for IEEE 1588 support. This LaunchPad presents a low-cost option for developers to evaluate Hercules MCUs and DP83630 Ethernet PHY to see if these Hercules MCUs meet their needs for their applications in industrial, automotive and other market segments.

The kit includes the LaunchPad development board with a USB debug cable and a quick start guide. For less than US$30, developers can get this feature-rich kit and start evaluation right out of the box using the pre-programmed safety demo and other downloadable software examples that include an Ethernet lwIP demo and a Wi-Fi® connectivity demo (based on SimpleLink™ Wi-Fi CC3100 BoosterPack).

Available in two versions, RM57Lx for industrial and TMS570LC43x for automotive applications, the kit is extremely easy to use just like other components in TI’s LaunchPad ecosystem. Both kits have two BoosterPack headers to add functionality using any number of compatible BoosterPacks.

Hercules RM57Lx and TMS570LC43x MCUs are suitable for performance-intense applications that require complex algorithms, real-time performance and floating-point processing. With CPU performance up to 330 MHz and a large amount of on-chip flash (up to 4 MB), these MCUs provide performance and memory headroom that customers may find compelling for their aerospace, railway, industrial and other programmable logic controller (PLC) applications.

The industrial Internet of Things (IoT) is an emerging area that these kits and supporting software can serve. The Hercules MCU – coupled with Ethernet connectivity via integrated EMAC, and Internet connectivity via a companion CC3100 Wi-Fi module –  will be attractive for industrial IoT applications that require a reliable, high-performance MCU as the central controller in a simple data aggregator or an IoT gateway.

The kits are available for order now on TI eStore. Get one today!

by using Bluetooth Smart in combination with full-duplex real-time communication

Authored by Uffe Bjorklund, founders and CEO of XSockets.NET. He has been working with development around real-time communication since 2009.

The SimpleLink™ multi-standard CC2650 wireless MCU from Texas Instruments is an amazing piece of hardware that enables communication over Bluetooth low energy as a peripheral device to a central unit. The SimpleLink SensorTag, based on the CC2650, has a lot of services and it would be great to be able to access the kit from anywhere in the world.

The mission

In this post we will take a look at how we can extend communication with CC2650 wireless MCU by adding a full-duplex communication layer behind the Bluetooth low energy central, so that we can read and write into CC2650 from anywhere in the world. Since this might feel a bit abstract the image below might help to visualize what we are going to do.

There are many ways to connect to a peripheral Bluetooth Smart device, but in this post we will be using a Raspberry Pi 2 as the BLE central device.

The image illustrates that the CC2650 wireless MCU communicates with the RaspberryPi over Bluetooth low energy. Then the Pi has a TCP/IP connection with XSockets (in this case using NodeJS) to be able to send/receive data in full-duplex. XSockets will then be able to send/receive data from any TCP/IP connection so that we can read/write to the CC2650 from anywhere. In the image above the clients is represented by a few selected ones, but it can be anything that has TCP/IP.

IoT & Real-Time Communication

In the world of the Internet of Things (IoT), real-time communication is almost a requirement. The most popular IoT protocols use full-duplex communication, and for a good reason. The IoT is often about sending data at a high frequency or receiving data when something happens. Solving this with a request response driven architecture is often a bad idea. With the half duplex technique you risk to get a very chatty solution with large overhead and messages that are sent when not needed.

Setting up the Raspberry Pi for Real-Time communication

Since the library we use to communicate with the SensorTag from the Raspberry Pi is based on NodeJS, we will use NodeJS for real-time communication as well.

Installing NodeJS

Installing NodeJS on a Raspberry Pi is very easy.

sudo wget http://node-arm.herokuapp.com/node_latest_armhf.deb 

sudo dpkg -i node_latest_armhf.deb

Then you can verify the version by running (and this will probably output v0.12.0 or higher)

node -v

The mission with this article is to show how to read/write in full-duplex to CC2650 from anywhere in the world. To be able to do so we need three parts.

1. A sensor client on the Raspberry Pi that communicates with the Bluetooth low energy device and also has a full-duplex connection to our real-time server.
2. A real-time server that can dispatch messages to the clients monitoring the sensors as well as dispatching messages to the sensor client when the monitoring clients want to write data to the sensor.
3. A monitoring client (can be several types) that display sensor data and send command to the sensor client via the real-time server.

These three implementations will be covered below.

Sensor Client

The sensor client (NodeJS) on the Raspberry Pi is pretty easy to build.

Setup

Create a folder called CC2650 and navigate to it.

Install SensorTag library

npm install sensortag

Install xsockets.net library

 npm install xsockets.net

Code

The complete code for the client (~70 lines) can be found in the github repository, but the important parts is covered here. Just place the app.js file in the folder where you installed the packages above.

Connection to server, note that the ip and port here is used for development only. When deployed to Azure the IP and port will be replaced with the public endpoint.

//Connecting to XSockets

var conn = new xsockets.TcpClient('192.168.1.3', 4502, ['sensor']);

//Getting the sensorcontroller

//The controller is used to listen for data as well as sending data

var sensorcontroller = conn.controller('sensor');

When temperature changes on the sensortag

    tagInstance.on('irTemperatureChange', function (ot, at) {

        //call server method 'irTempChange' and pass new value
        sensorcontroller.send('irtempchange', { obj: ot, amb: at });
    });

When a monitoring client enables IR-Temperature

     sensorcontroller.on('enableirtemp', self.enableIrTemperature);

When a monitoring client some where in the world disables the IR-Temperature

     sensorcontroller.on('disableirtemp', self.disableIrTemperature);                                                           

Real-Time Server

Since XSockets.NET has state, you can connect anything and it allows you to talk cross-protocol etc. it will be very easy to build the server-side communication.

Sensor Controller

This is the controller that the sensor client will use to send data to. The concept is simple yet efficient. When a sensor client send a message to the sensor controller, the message is dispatched to all clients having an instance of the monitor controller. This way all clients monitoring will get notifications about.

• Sensors that connect/disconnect
• Sensors that get IR-Temperature enabled/disabled
• Changed in temperature on the sensor

Monitor Controller

The monitor controller is even simpler than the sensor controller. This only has three methods.

• First one to be able to get information about all sensors being online (OnOpened).
• Second one for disabling the IR-Temperature notifications on the sensor.
• Third one for enabling the IR-Temperature on the sensor.

By passing in the connection id that we know from the sensor client the server can target the correct sensor to disable/enable.

Monitoring Client

Since you can connect anything to the real-time server (XSockets) you can control the sensor from pretty much anything. Your imagination sets the limits! In this sample I will only use a basic webpage and JavaScript to read/write data from the sensor.

Code

The complete code for the client can be found in the github repository, but the important parts is covered here.

Connection to server, note that the ip and port here is used for development only.

     //Connecting to XSockets

    var conn = new XSockets.WebSocket('ws://192.168.1.3:4502', ['monitor']);       
    //Getting the monitorcontroller
    //The controller is used to listen for data as well as sending data
    var monitor = conn.controller('monitor');

When the server send notificaiton about temperature changes

     monitor.on('irTempChange', function(d) {

        console.log('irtempchange', d);
        vm.update(d);
    });

Enable the IR-Temperature from the webpage

     monitor.invoke('enableIrTemp', vm.id());

Disable the IR-Temperature from the webpage

     monitor.invoke('disableIrTemp', vm.id());

When a monitoring client some where in the world disables the IR-Temperature

     monitor.on('irTempDisabled', function(id) {

        vm.disable(id);
    });

When a monitoring client some where in the world enables the IR-Temperature

     monitor.on('irTempEnabled', function(id) {

        vm.enable(id);
    });

Up & Running

An image showing the result from my development machine. We see the sensor tag connected over BLE to a Raspberry Pi that uses NodeJS to communicate with XSockets. Then XSockets sends data to all clients, in this case just a webpage. We can also enable/disable the sensors services directly from the webpage (or any other client).

Summary

The biggest challenge (for me) when building this was to setup BLE on the Raspberry Pi, but the reason for that is probably my limited skills in Linux and BLE. The Raspberry Pi 2 is extremely great to work with and the Texas Instruments SensorTag is very stable and easy to use. I also want to give some credit to Azure since deploying XSockets on Azure was extremely easy.

What’s next?

This post only uses the IR-Temperature service from the CC2650. We will continue to improve the solution and add support for more services as well as support for multiple SensorTags so that people around the world can register their own tags to be shown on Azure.

GitHub Repository

The complete solution is available on GitHubo 

Resources

• The sensortag lib on-top of Noble https://github.com/sandeepmistry/node-sensortag
• Noble https://github.com/sandeepmistry/noble
• Raspberry PI resources http://www.raspberrypi.org/downloads/
• Raspberry PI - Noobs setup http://www.raspberrypi.org/help/noobs-setup/
• The nodejs client for XSockets.NET https://github.com/XSockets/XSockets.Clients/tree/master/src/XSockets.Clients/XSockets4NodeJS
• About GATT at the Bluetooth Developer Portal https://developer.bluetooth.org/TechnologyOverview/Pages/GATT.aspx
• NodeJS tool for Visual Studio https://nodejstools.codeplex.com/
• Texas Instruments CC2650:  www.ti.com/sensortag
  
• Michael Saunby http://mike.saunby.net/2013/04/raspberry-pi-and-ti-cc2541-sensortag.html

To read the full article, visit the XSocket blog here.

Figure 1: Efficiency vs Output current for Wireless Power Receivers

Smartphones with integrated wireless charging capability have been on the market for several years now, with features and technology advancing swiftly with each new release.

While wireless power has many benefits (convenience, no connector, waterproof), users still want wireless chargers to charge at the same rate as when plugged into a cable. Today, this typically means charging at 5W, but pretty soon expectations will be charging times equivalent to those achieved from the “Fast charge” feature now being added to new high-end phones. In certain cases, you can achieve four hours of battery life in just 10 minutes. The new medium power (15W) specification which is about to be approved by the WPC will further support this capability

Several technical challenges are associated with designing even a true 5W wireless power system. Phones are getting thinner and the real estate within the phone is very important; the size and power dissipation of every component must be as low as possible. It is critical that the phone does not get hot – not only can it impact reliability, but it should not feel warm to the user.

A wireless power-charging solution is effectively an extra power stage within a phone, a new circuit to dissipate heat. The most popular wireless-power devices on the market today use a low-dropout regulator (LDO) instead of a switcher to feed the battery-charger circuit. It is higher efficiency and does not need a bulky inductor. To reduce the power dissipation of the LDO, it is critical to keep its on-resistance as low as possible and to minimize the current passing through it. The way to minimize the current at any given output power is to have a higher output voltage, and ideally to make this output voltage programmable. A programmable output voltage allows the circuit to be optimized by taking into account the input voltage range of the phones PMIC and the paramaters of the receiver coil.

TI’s bq51021 family of wireless chargers, including the bq51221 dual-mode (Wireless Power Consortium/Power Matters Alliance) compliant receiver, have been designed to enable true 5W charging. They feature the industry’s lowest Rdson and have an output voltage programmable from 5V to 8V. The bq51025 has an output voltage range up to 10V and the device can support 10W of power. The graph in figure 1 shows the efficiency of TI’s device vs load current and compares it to another product on the market.

As power levels continue to increase, thermal designs will become more challenging. This extra power will enable wireless charging times similar to the latest Fast charge features that now use only a wire.

Additional resources: 

• www.ti.com/wirelesspower
• www.ti.com/ldo

The field of embedded vision is growing rapidly with many cool vision-enabled products coming. If you’re involved with a product using embedded vision, here are a few helpful resources to bookmark:

The Embedded Vision Alliance (EVA): On the website for the EVA (www.embedded-vision.com) you’ll find lots of useful information to help you make the best embedded vision product possible. They have info on the latest news and trends in the industry, presentations from the recent Embedded Vision Summit and even free online training at the Embedded Vision Academy section. TI is proud to be a founding member of the EVA and you can find a lot of information on TI’s demos and libraries on the EVA site.

TI’s Vision Library: If you’re one of the many people using one of TI’s DSPs for embedded vision, then make sure you are familiar with our vision library (VLIB), which is available for free download here. Our VLIB has optimized building blocks for common vision functions like background modeling and subtraction, feature extraction, tracking, recognition and low-level pixel processing. Due to the need for high-performance, most customers in embedded processing prefer to use optimized routines like our VLIB routines rather than OpenCV calls.

Dream DSP: While not all the information here is geared specifically towards embedded vision, the DreamDSP page is a great source for information. You’ll find the latest news and information on TI’s DSPs, which are great processors for embedded vision applications. From here you can download our paper on embedded analytics, see TI Designs that can get you started, and watch videos showing how DSPs are used for analytics and TI’s role in the DSP space.

Speaking of videos, we have a new DSP Breaktime video out focused entirely on embedded vision. In this episode, Arnon and I discuss why DSPs are good for embedded vision, the Embedded Vision Alliance and OpenCV on TI’s processors. We even relate our movie topic to embedded vision.

Be sure to watch episode 4 and tell us about your cool embedded vision application.

At TI, we celebrate the makers and hobbyists who enjoy creating and innovating on their own time. In our ongoing DIY with TI series, we share their incredible Do It Yourself inventions using TI technology.

As TIer Uri Weinrib can attest, having a child brings so many new joys – and a few trifling frustrations – to life. Like when the store-bought mobile hanging over the baby’s crib stops after every song.

When Uri and his wife brought home their first child – a healthy little boy – they quickly learned that having to go in his room and turn on the mobile after every song was upsetting the baby because when he would see them, he would cry.

“He wants the music playing as he falls asleep. But the mobile plays just one song, and then you have to press the button again. So every time, I would have to stop what I was doing, go into his room and press the button again,” said Uri, a systems architect in wireless connectivity. “He would see me and burst into tears.”

This little frustration turned into inspiration: What if there was a way to control the mobile wirelessly from a website?

Around that time, we released the SimpleLink™ Wi-Fi® CC3200 single-chip wireless microcontroller (MCU). The device integrates an MCU with built-in Wi-Fi connectivity, allowing Uri to write code for the CC3200 Internet-on-a-chip™ device attached to the mobile to fully control the device from a smartphone or tablet.

But he didn’t stop there. The mobile came with four predefined songs. So, Uri added the capability to pick which song played, added more songs to the playlist and created a piano interface so he could edit or replace the songs, as his son got older. Uri attached a light sensor to the SimpleLink Wi-Fi CC3200 wireless MCU, enabling the light to automatically come on when the room was dark and even made it possible to change the mobile’s turning speed.

The project took Uri less than four months to complete during the rare free moments between juggling work and being a new dad. However, by the time the mobile was fully operational, Uri ran into another problem.

“My kid was too big for it,” he said with a chuckle.

“They said, ‘Wow, this kind of creativity would be great in the next stage of the toy industry. We want to move in this direction,” Uri said.

He’s now working with one company to integrate his creation into a technologically advanced children’s mobile for next year’s models – all because of one little fatherhood frustration.

How do you anticipate ringing in the active analog filter of your operational amplifier (op amp)? The purpose of analog filters is to remove signal in an intentional frequency band, not to inadvertently add additional ringing into the signal path. Consider looking at the value of Q, or quality factor, of each filter stage. Figure 1 shows an example of the characteristics of a second-order low-pass Butterworth filter.

Figure 1: Sallen-key, 6kHz low-pass filter using the WEBENCH® Filter Designer tool

 The header in Figure 1 provides filter topology, gain, cut-off frequency, Q and the minimum op amp bandwidth, in this case for the OPA124 precision op amp.

 These are all valuable entities when designing your filter, but let’s consider the Q in Figure 1, which is equal to 0.864. The value of Q is primarily dependent on the resistor and capacitor values in the circuit and relatively independent of the amplifier. This value of Q indicates that this system is underdamped. This unit-less variable actually quantifies the quality and amount of decay in the system. Q is related to ζ, the damping factor, by Q = 1/(2ζ). Each stage in multi-order filters generates its own Q factor.

If the maximum Q is less than 0.5, the system is overdamped. This type of system output does not ring at all. When the output voltage is displaced from its steady state, the filter’s output returns to its steady state with an exponential decay.

A Q value equal to 0.5 indicates that the system is critically damped. If you are designing a low- or high-pass filter, the first-order filters are the only filters that have a Q this low.

An underdamped circumstance occurs if Q is higher than 0.5. A Q greater than 0.5 indicates a lower rate of energy loss relative to the stored energy in the filter. At the output of these filter systems there will be a degree of ringing with input excitation. As the value of Q increases, it takes longer for the ringing to die out.

Figure 2 compares the low-pass filter responses of different Q values with respect to the frequency-domain and time-domain characteristics.

Figure 2: Impact of Q on the frequency response of low-pass filters (top) as well as the unit-step response (bottom) with a corner frequency of 1Hz

 The top plot in Figure 2 shows the level of filter gain overshoot versus frequency for various Q values. The combination of this gain/frequency response, combined with the impact on the phase margins, results in the ringing (bottom plot) that you see in your filter’s output.

 The most dramatic effect of higher Q values is the settling time, as seen in the bottom plot of Figure 2. The curve with a Q of 5 has considerable ringing compared to the Q with a curve of 0.707.

 The two filter systems in Figure 3 have differing maximum Q values. The filter with a higher Q value demonstrates more ringing with a step stimulus at the input of the filter.

Figure 3: Comparing the step response of second- and sixth-order 0.5 Chebyshev low-pass filters

In Figure 3, the input signal for these filters is a 0.5V square wave. The maximum Q factor with the left-hand curve is 0.8547. The initial overshoot is approximately 0.15V above the final settling voltage value of 0.5V. This curve quickly settles to its final value with very little ringing.

The Q factor for Figure 3’s right-hand curve is equal to 6.513. The initial overshoot is approximately 0.23V overshoot. This curve, with a higher Q factor, takes a little longer to settle, with eight visible cycles. As you design filters using WEBENCH Filter Designer, you will find the maximum Q value for the particular filter you choose to design.

So how high can Q become before it causes problems? In our industry, the consensus is that Q should be less than 10. But, beyond that, assess the characteristics and requirements of your circuit. From there, you can decide what is the maximum acceptable Q for your system.

Additional resources

• Find out about TI’s OPA124 precision op amp.
• Begin designing today with the WEBENCH Filter Designer.
• “Q – Quality Factor Tutorial” from Radio-Electronics.com.

Power density requirements for power supplies in cloud infrastructure end equipment like servers, Ethernet switches, base stations, and storage attach boxes is increasing. In response, the use of integrated MOSFET (Metal Oxide Semiconductor Field Effect Transistor) DC/DC converters for high-current POL (Point of Load) rails that have been traditionally served by PWM (Pulse Width Modulated) controllers with external MOSFETs has become mainstream. Also, the need to perform advanced tasks for high-performance processors and FPGAs like adaptive voltage scaling (Vout adjustment on the fly based on the processor operational profile to optimize power loss) has become important. Furthermore, power supply designers are increasingly focusing on eliminating external components, increasing reliability and preventing failures before they happen.

Today, TI offers the TPS544C20 and TPS544B20 power converters that combine these two very powerful ideas into a single IC.  On the one hand, they have integrated MOSFETs with enormously high 30A and 20A current-carrying capabilities, and on the other hand, they feature PMBus™ control.

What is ‘PMBus’ and why is it such a valuable power feature? PMBus, which stands for ‘power management bus,’ is the “remote control” of power management. PMBus control encompasses the powerful idea that you can control and program power management devices with software commands on the fly. This is not achievable in pure analog design where you would set the device behavior and select the resistors and capacitors at the design phase. With the PMBus protocol, a controlling processor can change things like the switching frequency, current limit and output voltage.  PMBus can also provide telemetry, which is reading things like IC temperature and current so that the processor can monitor the power system dynamically.

The idea of PMBus owes its origins to the popular I²C bus developed in the early 1980’s.  The I²C bus, which stands for inter-IC (integrated circuit), was a general-purpose bus to control and monitor any electronic system. It was a simple bus protocol replacing the many propriety protocols that existed at the time. From the I²C bus, came the SMBus protocol or the System Management Bus, defined in 1995. SMBus differed slightly from I²C as it added packet error checking, making it more robust. SMBus was used for PCs and servers but It was soon realized by the industry that the power management needs of systems is best served by a common protocol and set of standards, which culminated in the definition of PMBus control. PMBus, while using the SMBus as a physical layer, sets up the protocol for power management, replacing several propriety protocols.

TI’s SWIFT™ TPS544C20 and TPS544B20 are the industry’s first 4.5V to 18V, 30A DC/DC converters with integrated FETs and PMBus digital interface. To make it easy for an engineer to design with these products, we added support in WEBENCH® Power Designer. From within the WEBENCH tool you can exercise many of the PMBus commands and see the immediate impact, helping you quickly analyze and prototype the design.

As an example, let’s change the output voltage of a controller in real-time using PMBus commands. Let’s say you want to throttle down the performance of a microprocessor in a power-sensitive application, like a laptop, to save on battery life. As you know, power dissipation in a microprocessor is proportional to C V²f . Power dissipation depends on the square of voltage, so a reduction in voltage has an enhanced impact on reducing power. The microprocessor can dynamically issue a PMBus command to the power converter to reduce the output voltage via the PMBus bus. This Vout transition command is executed by the TPS544C20 or TPS544B20 to change its Vout.  The design steps are illustrated below.

I created a design with the TPS544C20 for nominal output voltage of 3.3V delivering an output current of 20A. Input voltage is 4.5V to 5.5V. In the advanced options I set the PMBus command Vref Margin Low to -16.67%, and the operation margin to “Margin Low” for lowering the output voltage (Figure 1).

Figure 1.  Set PMBus commands in the “Advanced Options” WEBENCH panel.

This sets up the TPS544C20 to transition Vout from the nominal value of 3.3V to 2.75V, which is 16.67% lower. You can simulate this effect in WEBENCH Power Designer using the online “Vout Transition” simulation (Figure 2).

Figure 2. Vout transition simulation.

If you zoom into the output voltage waveform, you will see the output voltage ripple along with the average Vout, which transitions from 3.3V to 2.75V. The operating value in the Op Val section indicates all variables for the new Vout.

Watch a video on how to create a design and run the Vout transition simulation.

Get a copy of the exact WEBENCH design I used in this video (it was created using the new “Share with Public” feature).

Try your hand at creating a PMBus system power design in WEBENCH Power Designer using the PMBus features and analyze the design with online SPICE simulations.

I’d love to hear from you—please drop your comments below.

Contrary to what you might be thinking, this blog is not a review or in-depth analysis about a technology from a long time ago in a galaxy far, far away. It’s about a technology that already exists and is gaining more presence in your everyday life: in your home, at the office and everywhere in between.

Power over Ethernet (PoE) is a technology that allows powered devices (PDs), such as IP phones, security cameras and wireless local area network (LAN) access points to receive power from power sourcing equipment (PSE) in parallel with data over standard CAT-5 Ethernet infrastructures.

Not too interesting, right? Actually, you’ll find that by integrating power and data, PoE has many benefits. It is cost effective because it only requires a single installation of data and power without needing an electrical technician. It is a flexible technology that gives you the mobility to install devices regardless of proximity to AC mains. It is a safe technology because the devices are isolated from the AC mains voltage. Plus, PoE is reliable because the PSE provides and monitors only the power that the PD requests.  Because of this flexibility, PoE is being implemented in emerging markets, such as set-top box, point-of-sale, industrial control, home automation and thin/zero client applications. 

With PoE technology evolving in 2017 due to the upcoming release of the IEEE 802.3.bt standard, which is capable of 90W, PoE will give rise to newer applications that use higher performance systems such as lighting and automotive. I know, 2017 seems far, far away, but you need high power today for your watt-hungry systems.

TI’s current solution to high-power PoE, in advance of the ratification of the IEEE802.3.bt standard, is Universal Power Over Ethernet (UPOE). UPOE is capable of powering up to 51W to the PD!

TI has released the TPS2378EVM-602, which enables full evaluation of a forced four-pair UPOE-compliant application. This app note, “Dual TPS2378 PD for 51-W High Power-Four Pair PoE,” offers a detailed discussion of UPOE and this evaluation module.

Need a PSE solution to put power on the cable? Use TPS23861EVM-612’s two high power ports, which don’t require configuration. Simply connect one of the high-power ports in the TPS23861EVM-612 to the TPS2378EVM-602 power+data input, and you will have an end-to-end forced UPOE solution for your next project.

Additional resources:

• Learn more about IEEE802.3btwith these blogs by TI’s David Abramson:
  • What’s next for PoE? IEEE802.3bt: November Plenary Session Recap
  • Mutual ID and its effect on backwards compatibility
  • 4PPoE task force discusses next-gen Power over Ethernet
• Read the TPS2378EVM-602 evaluation module user’s guide.  
• Check out a TI Designs reference design for a fully autonomous quad-port solution (TIDA-00290). 

In our ongoing series, ‘One to Watch,’ we profile the movers and shakers at TI who are making a difference through their extraordinary work.

TIer Ajinder Singh is described as equal parts engineer and leader. As the general manager of our building automation sector, a part of the Industrial Systems team, he still likes to get his hands dirty, dissect electronic devices to see how they work, and develop new TI Designs. At the same time, he also enjoys leading groups of people and working with customers to help solve their problems.

For these and other reasons, Ajinder has been named one of Fortune magazine’s 2015 “Accelerators” – five executives who are changing the face of Fortune 500 companies. You can read about his accomplishment in the latest print edition of Fortune, which was released today.

What are Ajinder’s thoughts about this high-profile recognition? Complete gratitude.

“I’m grateful that I discovered my passion right here at TI. And I’m grateful that the company gives me an opportunity every day to work on my passion,” he said Friday. “This way, everybody wins.”

Indeed, Ajinder’s passion shines through in his work, which allows him to drive real change in his organization and around the world. He and his team partner with building automation customers worldwide to understand their challenges and barriers to innovation, bringing together technologies from across TI’s broad portfolio of Analog and Embedded Processing products to help solve their problems. Their common goal? Build a future where innovative, smart buildings and homes can save us time and money – while decreasing our energy usage.

For example, last year, he and his team developed a TI reference design that takes indoor light, harvests it and can run a complete wireless sensing node.

“What we did with this design was show customers how we could harvest energy without batteries and send a Bluetooth Low Energy beacon every second,” Ajinder explained.

Bobby Mitra, who leads the industrial systems team, added: “Ajinder’s energy and passionate thought leadership – along with his deep system-level expertise – is an inspiring combination that’s leading to real breakthroughs and helping to drive longterm success at TI. He still likes to get his hands dirty and work on TI Designs, but he is also really passionate about helping develop the next generation of TIers.”

In fact, Ajinder is currently mentoring an intern on an even lower-power energy harvesting project using our next-generation low-power wireless radios and battery management devices.

Love of engineering

Ajinder’s career started with an internship at TI in 2002. That’s when he “got hooked” as an engineer, he said. As a member of the interface business unit, his task was to work on digital visual interface (DVI) receivers to solve a high-speed signal integrity issue.

“That’s what planted the seed and helped me discover who I am,” he said, adding, “I enjoyed interacting with so many smart people, and I received the guidance and mentoring I needed. The experience had a lot to do with the passion I have today for my work.”

Ajinder also credits his wife, Amrita, for inspiring him.

“She has helped me to solidify my passion for my work. Without her, I may not have been able to contribute as much as I have to TI.”

Originally from Delhi, India, Ajinder graduated from Texas Tech University with a master’s degree in electrical engineering and started working full time at TI in 2003. He served as a technology lead in building automation for a year-and-a-half and then started managing the team a year ago.

Turning passion into innovation

As a hobby, Ajinder dissects candy machines and remote-controlled cars. At his office, he cracks open smart building devices like Internet-connected thermostats, air-quality sensors and surveillance cameras to improve them, the Fortune article states.

“I’m always looking at what customers are doing with products, the capabilities of a TI device, and how it could simplify their products,” he said. “If we know the exact problem the customers are trying to solve sooner, then we can engage multiple customers and offer differentiated solutions.”

At work, he loves “taking on really complicated problems that customers are trying to solve and providing them with differentiated solutions” – using TI parts, of course.

“When we can talk to customers and engage them with a TI solution, we make a connection with them and we are all one. The combination of the TI differentiated solution and the humility of just sharing what we have done really resonates with our customers. We are trying to solve the same problems.”

From the next generation of occupancy detection to improved air quality sensing, Ajinder and his team are pushing the boundaries of innovation with our semiconductor products, laying the foundation for the future of connected, efficient buildings.

Accelerating the future

Those who know Ajinder say he was a prime candidate for recognition as an “accelerator.” Scott Roller, vice president of systems engineering and marketing, recognized Ajinder in an email to employees last week:

“It is wonderful to see Ajinder recognized for his natural passion for engineering and internal drive for constant improvement,” Scott said. “He brings so much energy to our team, and I look forward to seeing him continue to ‘accelerate’ building automation at Texas Instruments.”

Click hereto see the online version of the Fortune article.

Many elements go in to making excellent efficiency measurements in power supplies, but let’s concentrate here on temperature stabilization. Other concerns include quality and calibration of measurements and shunts. As efficiency requires two voltage and two current measurements, errors from the voltage and current meters used can stack up. With the best handheld meters (about $400 each) and diligent calibration, this “stack up” can be limited to about 1% in overall error. That error can be cut to be about 0.1% with higher-quality bench instruments and well calibrated shunts.

Resistivity of both copper and silicon increase about 10% per 25° C. Conduction losses are proportional to resistivity and account for over half of total losses in most power supplies. If you can get in the measurement well before the material heats up, you can get a better efficiency reading. But how much better?

Figure 1: Normalized power loss versus temperature in the CSD86350Q5D

Figure 1 shows a graph of losses versus temperature in CSD86350Q5D, a power stage similar to the one used in the power supply that I tested below. For each 25° C increase, losses increase about 5-6%. For inductors with combined DC, AC and core losses, a similar loss versus temperature relationship exists. For power supplies with efficiencies of about 90%, this 5-6% loss increase corresponds to about a .5% reduction in efficiency.

Our Power Design Services group has an automated efficiency tester for power supplies using a programmable source, a programmable load, four high-precision meters (Agilent 34401A), two calibrated shunts and a LabVIEW program to step the source load and collect the data. One concern I had was that data was being collected before the power supply had a chance to stabilize at a given load, thereby giving false efficiency readings. I decided to do some tests with the setup and vary the sequences and delays to see how much error was actually being introduced.

I used a convection-cooled (no fan) 12V to 1.2V TIDA-00324 design on a 6-inch x 6-inch board with a 50° C steady-state max temperature rise at 90A to serve as a near “worst-case” situation, so that premature readings would give false higher efficiencies. This is because larger boards have greater thermal time constants than smaller boards, and convection-cooled supplies take longer to stabilize than forced air-cooled supplies. Also, the greater the final temperature rise, the longer it takes to stabilize, and the greater potential for error. Designs more than 50°C that rise at the rated full load are generally not considered reliable.

I initially conducted three runs. The first was with the power-supply run at full load until stabilization, with data taken in 5A increments stepping down from a full 90A load to no load with 96 seconds between readings. This test took 30 minutes after stabilization and is the most “conservative” approach; with errors (if any) are efficiency readings that are too low.

The second run was a typical run on our setup where a cold supply is started up at no load and step-loaded in 5A increments to 90A. The only delay between readings is the measurement delay of the program, which turns out to be about 6 seconds per reading. This delay, coupled with the desire to get lots of readings, will be what actually significantly reduces error.

The third run was done to maximize “cheating” or measured efficiency at full load, where a cold supply is started up at full load (I took an initial reading) and then the load is stepped down in 5A increments.

Here are the results. I’ll discuss the “10-Minute Rule” plot referenced in Figure 2 later.

Figure 2: Efficiency versus load in the PMP10393, no fan, four measurement methods

As expected, errors are greatest at max load with efficiency reported 0.3% high in the typical case and 0.6% high where I tried to “cheat” the most. I also took thermal images of the board when reaching stabilization and when I got that 0.6% high efficiency reading (Figure 3).

Figure 3: PMP10393 at 90A no fan: steady state and after only 6 seconds at full load

There is about a 29° C difference. The 0.6% reduction in efficiency at steady state corresponds to a 7.3% increase in losses. This is consistent with a 5-6% increase in losses per 25°C.

The 0.3% error in the typical measurement method has to be compared against other possible errors in the measurements. If the meters are handheld and will cause about a 1% overall error, then this 0.3% is not a dominant issue. However, compared with a 0.1% error with high-grade bench instruments, this 0.3% is definitely significant.

Taking about 20 minutes for full stabilization and then slowly reducing the load will give the most reliable measurements.. I observed that if the power supply is run steadily for 4-5 minutes at full load, the efficiency readings will be within 0.1% of the final 90.12% value. With the average load being about one-half of the full load during a linear ramp-up to full load, I reasoned that by spreading the ramp-up over twice this 5 minutes for 10 minutes in all, will yield about the same accuracy.

I then went back to the typical setup where a cold supply is started up at no load and step-loaded in 5A increments to 90A, but added a measurement delay of 25 seconds per reading to get the full 90A load after 10 minutes. Spreading measurements evenly over time to reach full load after 10 minutes is what I will call the “10-Minute Rule” The 10-Minute Rule plot in Figure 2 is the result of this approach. Max error was less than 0.14%, which is less than the calibration error of a single Fluke 87V meter current measurement.

With a fan, I increased the max load to 120A to get the same 50° C rise in steady state at full load. Here, I was able to implement the “5-Minute Rule” to ramp from no load to the full 120A load in 5A increments over 5 minutes instead of 10 minutes. The error of the 120A efficiency reading at the end of 5 minutes was 0.13% (88.34% versus 88.21% steady-state efficiency). Hence, a 5-minute rule with forced-air applications will yield similar accuracy to a 10-minute rule in applications without a fan.

Because I performed my tests on a 6-inch x 6-inch board with a 50°C max full-load temperature rise in steady state, I would expect designs with smaller boards and lower max temperature rises to have less error, using the same 10-minute rule for applications without fan and the 5-minute rule for forced-air applications.

In summary, running power supplies on an automated efficiency tester setup as they are typically run with load gradually incremented from zero to full load, but with adding delays to target an overall 5 minutes test in the case of fan cooled power supplies and 10 minutes in the case of no fan will reduce errors due to temperature stabilization to 0.1% or less.

My colleague Collin Wells recently completed a blog series about 2-wire 4-20mA transmitters and their associated design challenges. The series concluded with a look at isolation schemes for 2-wire transmitters as defined by the American National Standards Institute (ANSI)/International Society of Automation (ISA)-50.1-1982 specification. After reading that post, I thought it would be beneficial to take a look at the same isolation schemes for 3-wire transmitters, which are used in the same sensor transmitter applications, except for high-power designs.

Figure 1: Simplified block diagrams of 2-wire and 3-wire transmitters

In one of my previous blog posts, I wrote about several architectures used for analog outputs in industrial automation. Figure 1 reiterates one of the key points I made in that post. As you can see, 2-wire transmitters use a single current loop for both power and ground, and therefore must consume less than 4mA of quiescent current (i_q). Some sensors, however, require more than 4mA of i_q and therefore the system must use a 3-wire sensor-transmitter approach, where power and signal current each flow in separate loops, allowing the sensor to consume as much current as necessary.

Figure 2: Non-isolated and input-isolated 3-wire transmitter block diagrams

Like 2-wire transmitter designs, an input-isolated scheme is sometimes required for 3-wire transmitters, usually when the sensor is conductively connected its measurement target which has a different ground potential than the PLC analog input. As illustrated in Figure 2, an input-isolated 3-wire sensor transmitter design receives power from the analog input or programmable logic controller (PLC) host. While the transmitter itself shares a ground with its host, the sensor resides on the opposite side of a digital- and power-isolation barrier.

Figure 3: Input-isolated 3-wire transmitter

Figure 3 shows an example design for an input-isolated 3-wire transmitter. This design uses a DAC8750 digital-to-analog converter (DAC), powered directly from the 3-wire transmitter supply, to provide the signal chain to create the standard industrial current outputs (DAC, reference voltage and high-side voltage-to-current converter). The DAC8750 also provides an internal low-dropout regulator (LDO) to supply its own digital core along with the transmitter side of the digital-isolation barrier provided by the ISO7641. The LM5017 buck regulator provides isolated power to the sensor side of the isolation barrier, derived directly from the 3-wire transmitter supply voltage. A high power-supply rejection ratio (PSRR) LDO, the TPS7A49, is used to clean up the isolated power for use in the sensor and ADC signal chain. The isolated power section of this design is derived from the evaluation board described in the LM5017 evaluation board user’s guide.

Input isolation is sometimes also required in PLC analog-output modules, although the architectures defined by the ANSI/ISA-50.1-1982 standard no longer apply. Typically this is because the PLC backplane ground is different than the load ground that the analog-output is driving. Figure 4 shows an example design.

Figure 4: Input-isolated PLC analog-output module

This design uses the same buck regulator as the previous design, the LM5017, to derive dual isolated supply voltages. The isolated supplies are followed by high-PSRR LDOs (TPS7A49 for the positive rail and TPS7A30 for the negative rail) to reduce ripple and derive +/-15V supplies for use with the DAC8760, which provides complete signal chains for standard industrial voltage and current outputs. The isolated power supply in this design is based on the ultra-small 1W, 12V-36V isolated power supply for analog PLC modules TI Design reference design.

Be on the look-out for more about isolation, as well as 4-wire transmitters in upcoming posts. If there is anything you’d like to hear more about concerning isolation for analog outputs in industrial automation, post a comment below.

While browsing the QNX website, I was happy to find out that QNX now has a Neutrino 6.6.0 Board Support Package (BSP) for the AM437x EVM. 

You can find it here: http://community.qnx.com/sf/wiki/do/viewPage/projects.bsp/wiki/TiAm437xGp_evm 

QNX offers solutions for automotive, industrial, medical, networking, telecommunications, security & defense.

Father’s Day is just a few days away. If you haven’t picked up something for dad yet, we have some inspiring ideas, both big and small, that have TI technology in them.

Olio Model One smartwatch

The Olio Model One is the first watch designed to save you time, so you can focus on what matters most. Command and control your digital life with a limited edition timepiece that blends uncompromised quality, intelligent connectivity and enduring style.

Each Olio Model One is crafted from cold forged 316L stainless steel and features a high-resolution touch sensitive LCD display. Olio’s watch faces use data from your phone or Bluetooth devices to provide a glanceable view of your notifications, upcoming schedule or the weather.

As you use your Olio Model One, it develops an understanding of your preferences, and using your current context, it begins to offer insightful suggestions to help you stay focused. It may, for example, suggest to hold your calls while you are in a busy meeting or prompt you to pack an umbrella on a rainy day.  

The Olio Model One is powered by the TI’s Sitara™ AM3703 processor, designed to provide best-in-class graphics performance while delivering low-power consumption.

Shipping this summer, the watch is available for pre-order now and comes in steel and PVD-coated black. It starts at $595 and works with iOS and Android.

Leikr GPS sportswatch

If you’re looking for something sportier than the Olio, check out the Leikr Sports Watch, designed for running, cycling and endurance sports. A high-sensitivity GPS receiver can measure distance, speed, pace, heart rate and more in real time.

Created in Denmark, the GPS watch features a 2-inch glass screen that can display color road maps and other metrics.

The integration of readable road maps, trails and other navigation landmarks is what sets Leikr apart from other products. So, if you’re directionally challenged and don’t want to run with a smartphone, this watch can help you find your way back home.

The watch contains a TISitaraAM335x processor.

“The high integration and low-power consumption of TI’s AM335x family of Sitara processors, paired with the creativity of Leikr engineers, made possible for Leikr to bring this innovative product to market,” said Rogerio Almeida in TI Catalog Processor Business Development.

The watch costs about $300 through Leikr.

SMART kapp digital white board

SMART kapp is a Bluetooth-enabled dry-erase board that allows you to capture, save and share your ideas wirelessly.

The device can improve collaboration in different locations. For example, you can brainstorm on a project by sketching it out on the board and share your work with your colleagues in real time. Or, you can help your kids with a homework problem while you are away from home.

“The SMART kapp digital white board truly redefines collaboration in the digital age,” said Artem Aginskiy, TI business development manager in the Catalog Processor group. “I am excited to see this level of innovation enabled by TI processors.”

Cost: $899 U.S./$999 CDN through various retailers.

HP Sprout

Sprout is Hewlett Packard’s (HP’s) all-in-one Windows 8 personal computer with a DLP^® Pico™ technology enabled projector that uses TI's 0.45" WXGA chipset.

Sprout contains Intel’s RealSense technology, which features nine TI devices.

Sprout costs $1,899. Learn more about Sprout.

BMW 2-series convertible

The sporty new BMW 2-series convertible features a new head unit powered by TI’s “Jacinto” family of infotainment processors.

The TI infotainment processors behind the head unit use the “Jacinto” mutli-core heterogeneous architecture, leveraging the latest generation ARM® Cortex®-A15 multicore CPUs and Imagination Technologies multicore 3D Graphics on OMAP5, and DRA65x “Jacinto 5” for advanced sound and audio capabilities. This architecture, leveraging OMAP5 for user-interface and “Jacinto 5” for vehicle interface functions, allows each to perform at the peak of their capabilities without compromising performance.

Hello and welcome back to the “Timing is Everything” blog series. In a previous post, Timothy T. talked about the clocking requirements of the JESD204B interface standard that is gaining popularity for its ability to simplify design in high-speed data acquisition systems. In this post, I’m going to talk about the different system reference signal (SYSREF) modes of jitter synthesizers and cleaners, as well as how to use them to maximize the performance of your JESD204B clocking scheme.

The LMK04821 family of devices provide a good case study for this topic because they are high-performance, dual-loop jitter cleaners that can drive up to seven JESD204B converters or logic devices in a subclass-1 clocking scheme with device and SYSREF clocks. Figure 1 is a high level block diagram of a typical JESD204B system with the LMK04821 family devices as clocking solution.

Figure 1:Typical JEDEC JESD204B application block diagram

The LMK04821 generates SYSREF signals with a single SYSREF clock divider from the voltage-controlled oscillator of the second phase-locked loop (PLL) . From the divider, the signal gets distributed to the individual output paths. Each output path contains digital and analog delays to adjust the SYSREF phase in relation to the device clock.

From the JESD204B standard, SYSREF can be in different modes, as shown in Figure 2. It can be a continuous (also known as periodic), gapped periodic or one-shot signal. The continuous and gapped-periodic SYSREF periods must be in an integer multiple of the local multiframe clock (LMFC) in order to avoid SYSREF pulses in the middle of a multiframe.

Continuous mode allows for continuous output. Many developers don’t use continuous mode due to crosstalk from SYSREF to the device clock. However, continuous mode enables the system developers to manually set up the correct deterministic-phase relationship between both signals. After the setup it can be changed to gapped-periodic SYSREF.

In gapped-periodic or one-shot modes, the output of the SYSREF clock divider is fed through a pulser to the output paths. The pulser gates the SYSREF signal and lets only a few pulses through. The pulse count can be set to one, two, four or eight pulses. Since there isn’t a periodic signal, the crosstalk from SYSREF to the device clock is minimized.

Another type of gapped-periodic SYSREF mode in the LMK0482x is the request mode, which outputs a continuous stream of SYSREF pulses as long as the SYNC/SYSREF_REQ pin is high.

Figure 2:The SYSREF modes of the LMK0482x are a) continuous SYSREF, b) pulsed SYSREF (one-shot or gapped periodic), c) and SYSREF request (gapped periodic)

In LMK04821 devices, the internal SYSREF distribution path is shared with the output-divider synchronization path. Therefore, it needs a specific register write sequence to enable synchronized outputs and glitch-free SYSREF pulse generation. In Table 1, the methods I’ve described are listed with their register write sequences. Table 1 also shows the internal-register field names with content as a decimal value. Steps with the same number are interchangeable.

Table 1:Register write sequences to enable different SYSREF modes

 The JESD204B standard is reducing the layout efforts while introducing serialized data transmission between signal converters and logic devices. By taking full advantage of the SYSREF modes of your JESD204B-enabled clock device, you can easily create deterministic phase relationships in the whole system.

 Are there other clock design challenges you’d like us to cover regarding JESD204B designs or others? Let me know by logging in to post a comment below.

 Additional resources

• Read the blog series about JESD204B subclasses.
• Read this blog post about JESD204B subclass-1 clocking timing requirements.
• Read Thomas Neu’s white paper, “Ready to make the jump to JESD204B?”
• Read this Analog Applications Journal article, “When is the JESD204B interface the right choice?”
• Get useful design tips on various clock and timing design challenges from the “Timing is Everything” blog series.

It’s true! If you were thinking about your new design that requires an application processor, be sure to check out the Sitara AM437x processors! They are a scalable, pin-compatible processor family in production since April of this year. There are several options to choose from including the new economical 300MHz option, AM4376 (AM4376BZDND30), which sells for $7 in volume.

The AM437x family has offerings in 300MHz, 800MHz and 1GHz options and well as optional 3D graphics acceleration for enhanced user interfaces. The AM437x processors are also offered in commercial (0 to 90C), industrial (-40 to 90C) and extended (-40 to 105C) junction temperature ranges.  The AM437x processors integrate support for industrial protocols for automation and industrial drives making them ideal for applications such as building automation, telecom infrastructure, industrial tools, and more.

You can evaluate the Sitara AM437x processors with the AM437x evaluation module or the AM437x industrial development kit and decide which Sitara AM437x variant is best for your new design.

 What will you develop with your new AM4376 processor?

Lithium-based chemistries are the most widely used cells in portable electronics, but other chemistries also are popular in automotive, industrial and portable-electronics applications. The maximum operating voltage varies from 3.6V to 4.35V for lithium-based cells, to under 1.5V for nickel-metal hydride (NiMH) and nickel-cadmium (NiCD) cells, to over 13V for a stack of six lead-acid (PbA) cells. Many automotive and industrial applications have system requirements where pack voltages can reach 50V and even exceed 100V.

In addition to high-voltage requirements, these automotive and industrial applications typically must support aggressive load-current profiles. Transient loads can be difficult to gauge, and it is common for the state-of-charge (SOC) to jump as loads pulse and vary in intensity. Here at TI, we have added gauging-performance improvements to our Impedance Track™ gauging algorithm that prevent state-of-charge jumps. We also added a capacity-smoothing filter to support aggressive transient-load conditions.

Figure 1 illustrates an example of gauging a transient-load profile with a typical gauge and the same profile with a smoothing filter. The smoothing filter provides a clean state-of-charge curve for the discharge profile.

Figure 1: A very aggressive pulsed-load profile (a) and the same pulsed-load profile with smoothing (b)

Gauges typically remain coupled to one set of batteries for the life of the pack, but some systems have replaceable cells. This presents a challenge for the gauge to reinitialize the Ra table and Qmax that it learned from the old battery. The gauge limits how much the Ra table and Qmax can change, so large changes to initialize a new battery can be disqualified. You must modify some gauging parameters to allow learning in a “host-side” system.

If you have an application with high voltages, aggressive load profiles or host-side system support, consider the BQ34Z100-G1 for the gauging device. This gauge can support lithium-ion (Li-ion), lithium-ion phosphate (LiFePO4), PbA, NiMH, NiCD and some primary cell chemistries; it also automatically reconfigures most parameters based on the chemistry programmed into the device.

Additional Resources

• Check out TI’s battery management solutions portfolio: www.ti.com/battery.
• Watch a quick introduction to bq34z100-G1