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POET Technologies Inc of Toronto, Ontario, Canada — designer and developer of the POET Optical Interposer, photonic integrated circuits (PICs) and light sources for the hyperscale data-center, telecom and artificial intelligence (AI) markets — has closed a non-brokered financing with a single institutional investor. In a private placement, the firm issued and sold 13,636,364 common shares and one common share purchase warrant (at a combined price of US$5.50 each) for gross proceeds of US$75m, before deducting related expenses...

High school trigonometry combined with four-quadrant multipliers can be exploited to yield sinusoidal frequency doublers. Nothing non-linear is involved, which means no possibly strident filtering requirements.  

Starting with some sinusoidal signal and needing to derive new sinusoidal signals at multiples of the original sinusoidal frequency, a little trigonometry and four-quadrant multipliers can be useful. Consider the following SPICE simulation in Figure 1.

Figure 1 Two analog frequency doublers, A1 + U1 and A2 + U2, in cascade to form a frequency quadruple.

The above sketch shows the pair A1 and U1 configured as a frequency doubler from V1 to V2, and the pair A2 and U2 configured as another frequency doubler from V2 to V3. Together, the two of them form a frequency quadrupler from V1 to V3. With more circuits, you can make an octupler and so on within the bandwidth limits of the active semiconductors, of course.

Frequency doubler operation is based on these trigonometric identities:

sin² (x) = 0.5 * ( 1 – cos (2x) )  and  cos² (x) = 0.5 * ( 1 + cos (2x) )

sin² (x) = 0.5 – 0.5 * cos (2x)   and  cos² (x) = 0.5 + 0.5* cos (2x)

Take your pick, both equations yield a DC offset plus a sinusoid at twice the frequency you started with. Do a DC block as with C1 and R1 above, and you are left with a doubled-frequency sinusoid at half the original amplitude. Follow that up with a times two gain stage, and you have made a sinusoid at twice the original frequency and at the same amplitude with which you started.

This way of doing things takes less stuff than having to do some non-linear process on the input sinusoid to generate a harmonic comb and then having to filter out everything except the one frequency you want.

Although there might actually be some other harmonics at each op-amp output, depending on how non-ideal the multiplier and op-amp might be, this process does not nominally generate other unwanted harmonics. Such harmonics as might incidentally arise won’t require a high-performance filter for their removal.

John Dunn is an electronics consultant, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York University (MSEE).

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New Simulation & Optimization Platform Enables Custom Coil Designs for Industrial, Robotics and Medical Systems

Renesas Electronics Corporation introduced a new family of magnet-free inductive position sensor (IPS) ICs that can be fully customized for various coil designs compatible with a wide range of industrial applications such as robotics, medical and healthcare, smart buildings, home appliances and motor commutation. Built for high resolution, precision, and robust performance, the new RAA2P3226, RAA2P3200, and RAA2P4200 sensor ICs offer a cost-effective alternative to traditional magnetic and optical encoders, which can be bulky, expensive, and require frequent maintenance. Renesas also launched a web-based design tool that allows customers to easily create custom sensing elements to meet their specific system needs.

Operating on non-contact coil sensor technology, Renesas IPS products use a simple metallic target and dual-coil or single-coil configurations to detect absolute rotary, linear, or arc positions. These sensor ICs are designed to maintain stable operation even in environments with elevated temperatures (-40 to 125°C), particulate matter, moisture, mechanical vibration and electromagnetic interference. Moreover, they are immune to stray magnetic fields and require no maintenance, unlike magnetic- or optical encoder-based sensors. Their durability and low upkeep make them a reliable and cost-effective sensing solution for motor drives, actuators, valves, service robots and infrastructure applications, where reliability and long-term performance are critical.

All three products offer high precision in detecting target positions, with accuracy better than 0.1 percent of the full-scale electrical range. Two of the products, the RAA2P3226 and RAA2P3200 operate at 600K RPM (electrical) with propagation delays under 100ns, which is imperative in high-speed motor applications. The advanced RAA2P3226 supports dual-coil sensing with up to 19-bit resolution and 0.01° absolute accuracy, providing the high-precision performance required for robotic applications. The RAA2P4200 targets low-speed applications such as medical devices and power tools and the RAA2P3200 is optimized for high-speed motor commutation. All three products include automatic calibration and linearization to simplify integration and improve system-level performance.

In addition to these three products, Renesas will also introduce automotive-grade IPS, RAA2P452x and RAA2P4500. The dual-channel RAA2P452x allows customers to achieve ASIL D safety compliance when paired with Renesas MCUs. This automotive-grade solution offers a cost-effective option for low-speed body control and chassis systems without compromising quality.

Designing with inductive position sensors typically involves integrating a PCB, an IC with passive components, and a metal target mounted to the moving part. The most complex part is the external sensing element, such as the transmitter and receiver coils, which must be precisely configured to realize accuracy and customized to the system’s mechanical and environmental requirements. Renesas’ web-based Inductive Position Sensor Coil Optimizer tool tackles this challenge by automating coil layout, simulation, and tuning, significantly reducing the learning curve for developers. With this tool, engineers can also obtain accurate performance estimates and overcome manufacturing constraints by optimizing the coil layout.

“Our new web-based coil design tool is a game changer for inductive position sensing,” said Leopold Beer, Vice President of the Sensors Division at Renesas. “In the past, developers had to rely on chip suppliers for technical expertise when working with inductive position sensors. We completely removed this hurdle. This intuitive tool lets developers fully customize the sensing element and automatically fine-tunes it to achieve maximum accuracy and robustness at the system level. This dramatically lowers the barrier of entry and enables more customers, regardless of their expertise level, to confidently integrate inductive position sensing into their designs.”

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Learn how Narrowband (NB)-IoT offers power-efficient, scalable connectivity for IoT and smart cities. It addresses challenges of power, coverage, and cost for massive device deployments.

Melexis introduces the MLX90514, a dual-input inductive sensor IC that simultaneously processes signals from two sets of coils to compute differential or vernier angles on-chip. The inductive sensor targets automotive applications, such as steering torque feedback, steering angle sensing, and steering rack motor control.

(Source: Melexis)

Traditionally, designers have combined two single-channel ICs or used magnetic sensors for many applications, Melexis said. However, with the move to electrification, autonomy, and advanced driver-assistance systems (ADAS), vehicle control systems have become more complex particularly in systems such as steering torque feedback, steering rack motor control, including steer-by-wire implementations, which need dual-channel position sensing to deliver accurate torque and angle measurements.

By integrating differential and vernier angle calculations on-chip, the MLX90514 reduces processing demands on the host system, enabling smaller and more streamlined sensor designs. By computing complex position information (such as differential or vernier angles) directly at the sensor it eliminates the need for multiple ICs, which reduces design complexity and component count.

The MLX90514 is Melexis’ first dual inductive application-specific standard product (ASSP). It offers several interface options—including SENT, SPC, and PWM for a standalone module, and SPI for embedded modules—with integrated on-chip processing. The SENT/SPC output accommodates up to a 24-bit payload, enabling high-fidelity transmission of two synchronized 12-bit channels, which is required for high-accuracy torque and angle sensing.

Key features include zero-latency synchronized dual-channel operation, external pulse-width-modulation (PWM) signal integration that allows reading PWM signals from external sources, and the capability to handle small inductive signals, which supports compact coil designs and tighter printed-circuit-board layouts for smaller sensing modules.

The MLX90514 enables ASIL-D-compliant sensing systems, as a Safety Element out of Context (SEooC), for automotive steering torque and angle applications. The inductive interface sensor is available now.

The post Dual-input inductive sensor simplifies design appeared first on EDN.

As you can see it's a green little toroid with a "secondary" made using green metal wire used for flowers etc 3 windings. Gave the coil some 19MHz 24VPP Sinus wich gave me a result of 5.89VPP 19MHz on osciloscope but with multimeter i got 149.9V in both AC and DC. submitted by /u/Whyjustwhydothat [link] [comments]

A team of researchers has created a sealed, durable, and rapid tactile interface for on-screen Braille, offering a new approach to tactile accessibility.

Schneider Electric offers two reference designs co-engineered with NVIDIA to accelerate deployment of AI-ready infrastructure for AI factories. The controls reference design uses a plug-and-play MQTT architecture to bridge OT and IT systems, enabling operators to access and act on data from every layer.

The first reference design integrates power management and liquid cooling controls with NVIDIA Mission Control software, enabling smooth orchestration of AI clusters. It also supports Schneider’s data-center reference designs for NVIDIA Grace Blackwell systems, giving operators precise control over power and cooling to meet the demands of accelerated AI workloads.

The second reference design supports AI factories running NVIDIA GB300 NVL72 systems at up to 142 kW per rack. It delivers a complete blueprint for facility power, cooling, IT space, and lifecycle software, compatible with both ANSI and IEC standards. Using Schneider’s validated models and digital twins, operators can plan high-density AI data halls, optimize designs, and ensure efficiency, reliability, and scalability for NVIDIA Blackwell Ultra systems.

For more information about these new reference designs, as well as other data-center reference designs developed with NVIDIA, click here.

Schneider Electric 

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ST’s L98GD8 multichannel gate driver offers flexible output configurations in 48-V automotive power systems. Its eight independent, configurable outputs can drive MOSFETs as individual power switches or as high- and low-side pairs in up to two H-bridges for DC motor control. The device also supports peak-and-hold operation for electrically actuated valves.

Programmable gate current helps minimize MOSFET switching noise to meet EMC requirements. The driver operates from a 3.8-V to 58-V battery supply and a 4.5-V to 5.5-V VDD supply. Its I/O is compatible with both 3.3-V and 5-V logic levels.

To ensure safety and reliability, each output provides comprehensive diagnostics, including short-to-battery, short-to-ground, and open-load conditions. Output status is continuously monitored through dedicated SPI registers. The L98GD8 features fast overcurrent shutdown with dual-redundant failsafe pins, battery undervoltage detection, and an ADC for monitoring battery voltage and die temperature. Additional safety functions include Built-In Self-Test (BIST), Hardware Self-Check (HWSC), and a Communication Check (CC) watchdog timer.

The L98GD8 driver is available now, with prices starting at $3.94 each in lots of 1000 units.

L98GD8 product page 

STMicroelectronics

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According to Thales, its MultiApp 5.2 Premium PQC is Europe’s first quantum-resistant smartcard to receive high-level security certification from ANSSI (the French National Cybersecurity Agency). Certified to the EAL6+ level under the Common Criteria framework, the smartcard also uses digital signature algorithms standardized by NIST in the U.S.

The MultiApp 5.2 Premium PQC leverages post-quantum cryptography to protect digital identity data in ID cards, health cards, and driving licenses. This new generation of cryptographic signatures is designed to withstand the vast computational power of quantum computers, both today and in the future.

“This first certification for a solution incorporating post-quantum cryptography reflects ANSSI’s commitment to supporting innovation, while upholding the highest cybersecurity standards,” said Franck Sadmi, Head of National Certification Center, French Cybersecurity Agency (ANSSI). “The joint work of Thales, CEA-Leti IT Security Evaluation Facility, and ANSSI is a strong signal that Europe is ready to lead the way in post-quantum security, enabling organizations and governments to deploy solutions that anticipate future risks, rather than waiting for quantum computers to become mainstream.”

Thales

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Joining Omnivision’s Nyxel NIR line, the OX05C1S global-shutter HDR image sensor targets in-cabin driver and occupant monitoring systems (DMS and OMS). The 5-Mpixel sensor, with 2.2-µm backside-illuminated pixels, captures clear images of the entire cabin, enhancing algorithm accuracy even under challenging high-brightness conditions.

The OX05C1S leverages Nyxel technology to achieve high quantum efficiency at the 940-nm NIR wavelength, improving DMS and OMS performance in low-light environments. On-chip RGB-IR separation reduces the need for a dedicated image signal processor and backend processing.

With package dimensions of 6.61×5.34 mm, the OX05C1S is 30% smaller than the previous-generation OX05B (7.94×6.34 mm), providing greater mechanical design flexibility for in-cabin camera integration. Lens compatibility with the OX05B enables reuse of existing optics, simplifying system upgrades and reducing overall design cost.

The OX05C1S sensor is offered in both color filter array (RGB-IR) and monochrome configurations. Samples are available now, with mass production scheduled for 2026.

OX05C1S product page  

Omnivision

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Expanding its line of inductors and frequency control devices (FCDs), Vishay has added more than 2000 new SKUs across nearly 100 series. The broader offering simplifies sourcing and supports more applications with wider inductance and voltage ranges, improved noise suppression, and additional sizes for compact PCB layouts.

Recent additions include wireless charging inductors, common-mode chokes, high-current ferrite impedance beads, and TLVR inductors, along with nearly 15 new FCD products. To meet the demand for diversified manufacturing, the company is expanding production in Asia, Mexico, and the Dominican Republic. IHLP series power inductors are now shipping from the company’s Gomez Palacio, Durango, Mexico facility.

Product rollouts will continue through 2025, with additional series scheduled to launch in the coming months. In total, Vishay expects to surpass 3000 new SKUs of inductors and FDCs, supporting design activity across industrial, telecom, and consumer markets.

Vishay Intertechnology  

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One of the first jobs I had, when I first got out of college, was for a company that designed and manufactured monitors for large trucks, the kind used in mining operations. This company was a small entity with around 25 employees and a couple of engineers. The main product was a monitor that sat on the dash of these trucks and watched over things like oil pressure, coolant temperature, and level, hydraulic pressure, etc. Variations of this monitor had 4, 5, or 6 indicator lights that lit if the monitored point went out of spec. An alarm also sounded, and the truck was shut down by a relay connection.

Do you have a memorable experience solving an engineering problem at work or in your spare time? Tell us your Tale

Another engineer and I decided it was time to bring this analog monitor into the microprocessor era. The idea was to monitor the same functions, but only have one indicator light with an LCD showing the issue. Along with the alarming function, we could also add more information on the LCD, like temperatures and pressure readings. It wasn’t a very complex design. At that time, micros didn’t typically have watchdog circuits, so we added one of the few external watchdogs available at the time. Our concern was that some transient would throw the micro off course, and we wanted the watchdog to reset the monitor in that case. The 24-V input voltage and all sensor inputs had some level of transient suppression (but, after several decades, I have forgotten what the circuit consisted of).

We completed a design, and it worked very well on the bench. Next, we hit it with various transients that we could generate. Not having access to any transient test equipment, we had to invent some methods to test this. Worse, we had no specs or general information on what kind of transients these trucks can experience, but we ourselves were satisfied that it was ready for a beta test.

After testing, we sent the monitor to a local mining company to have it installed on a working truck. We also sent a harness system with leads long enough to get to the sensors located around the truck. The company called us after they got the monitor mounted on the dash and all the sensors wired to the harness, so a visit was scheduled to test the monitor on a running truck.

I need to stop at this point to describe the truck. It was a 175-ton dump truck. There are bigger trucks now, but it was very large for the time. Picture tires 10 feet high and a 1600 HP diesel/electric generator system powering electric motors turning each wheel. The driver’s cab was about 18 feet off the ground and was reached using an attached ladder. The driver and the two of us climbed this ladder to begin the test.

To add to the pressure, there were a dozen or so managers and workers on the ground watching the tests. The mining company managers gave the go-ahead to begin. The driver started the truck (quit a roar)—the monitor fired up, and the LCD began showing the status of the monitored points… great!

After a few seconds, the truck shut down… not great. We looked at each other—a few seconds later, the truck roared alive again—monitor working—a couple more seconds, the truck shuts down—a few seconds later, the truck restarts, etc., etc., etc.

After a half dozen of these cycles, we told the driver to shut the truck down. We couldn’t tie up the million-dollar truck any longer, so we could not do any more investigation. We packed up our equipment and left with our heads down.

Back at the shop, we talked through what went on. We concluded that the monitor’s micro was disrupted by an unknown transient. The watchdog then discovered the code running amok and tripped the shutdown relay. The watchdog then rebooted the micro, resetting the relay, which allowed the truck to restart itself.

One of the major design issues was that some sensors required tens of feet of wire and were unshielded single leads (most sensors used chassis ground). These single wires (or should I call them antennas) could have been close to various relays and electric actuators on the truck, or worse yet, near the cabling used for the generator-to-motor system. Also, the watchdog, which did discover the issue, did not fulfill its function—it allowed the truck to restart.

This is where “Tales from the Cube” articles tell us how they fixed the issue by adding a larger resistor, fixing a bad solder joint, or reworking a reversed diode. In this tale, there is no happy ending. The boss didn’t want to continue with the project, and I’m sure the customer was not impressed. The project was cancelled. So why did I write this up?

I thought it was a good example of what can happen on engineering projects—sometimes they fail (moving from the lab to the field often exposes design issues), and sometimes you don’t get a chance to fix the design. Young engineers should understand this and not be disenchanted when it does. Don’t let it get you down. Remember, we learn a lot by failure.

Shortly after this project, we got the opportunity to design a full, micro-based dashboard for a large articulated truck. One of the things we designed was a fiber-optic cable data-transfer system to the back portion of the truck. This minimized the length of sensor wires, providing antennas for the transient. In this design, the system worked flawlessly.

Damian Bonicatto is a consulting engineer with decades of experience in embedded hardware, firmware, and system design. He holds over 30 patents.

Phoenix Bonicatto is a freelance writer.

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The post Watchdog versus the truck appeared first on EDN.

Not to sure if this belongs here but i aquired these with an order of vintage NOS. I am trying to find a way to scan these and digitize them correctly. Ill post or link the scans once i can get them done. submitted by /u/Independent-Gazelle6 [link] [comments]

submitted by /u/Electro-nut [link] [comments]

Due to rapidly increasing demand, particularly in the optical communications field, Tokyo-based JX Advanced Metals Corp is to make a further capital investment to increase the production of indium phosphide (InP) substrates at its Isohara Plant in Kitaibaraki City, Ibaraki Prefecture...

The IEEE International Electron Devices Meeting (IEDM) is considered the premier forum where scientists and engineers come together to disclose, discuss, and debate the best recent R&D work in electron devices, semiconductors, and microelectronic technologies. The 71st annual IEEE IEDM conference will be held December 6-10, 2025, at the Hilton San Francisco Union.

Supporting the theme “100 Years of FETs: Shaping the Future of Device Innovations,” the 2025 IEDM technical program will consist of 295 presentations, plus a host of events.

“This year’s IEDM offers a preview of the next computing paradigm. We are witnessing the convergence of atomic-scale fabrication, 3D integration, and neuromorphic design, moving us beyond yesterday’s technology and even classical computing. From monolithic CFETs that redefine transistor density to in-memory computing that can mitigate the von Neumann bottleneck, more intelligent and more efficient technology is being built here,” said Gaudenzio Meneghesso, IEDM 2025 Publicity Chair, and Head of the Department of Information Engineering at the University of Padova.

“As AI is demanding unprecedented efficiency, the device community is rising to the challenge. IEDM 2025 showcases technologies that can power the next AI decade: from GaN chiplets for power delivery and silicon photonics for data transfer to 3D DRAM and FeFETs for in-memory computing. These device technologies will make the algorithms of tomorrow possible.”

“The pursuit of Moore’s Law has evolved from a simple race to shrink transistors into engineering in multiple dimensions. IEDM 2025 showcases this new era: we are scaling up with 3D stacking like CFETs and 3D DRAM, scaling laterally with atomic-layer-deposited channel materials, and scaling past CPUs with novel architectures like in-memory computing,” said John Paul Strachan, IEDM 2025 Publicity Co-Chair, Director of Peter Grünberg Institute, Forschungszentrum Jülich, and Professor at RWTH Aachen University. “This is the culmination of a century of FET innovation, pushing the boundaries of what is physically possible to compute.”

The post IEEE IEDM, 2025 Showcases Latest Technologies in Microelectronics, Themed “100 Years of FETs” appeared first on ELE Times.

DigiKey is known for comically over-packing their orders. A regular $50 order usually leaves you with a lifetime supply in ESD bags and packing material. But today they really went "hold my beer!". submitted by /u/Defiant-Appeal4340 [link] [comments]

I wanted to start a small side project to 'calm down' from my last big one. And because we need something to replace the old FM radio in our dining room, I started building this, an active smart speaker. Currently, I have what you can see on the pictures. I pulled all the parts out of an old multimedia system my mother gave to me. The donor-board can be seen on one of the pictures. It was to big to fit in the speakers I am planing to use, so I decided to split it up by transferring the components onto a self soldered PCB and throwing out unnecessary parts out in the process. The amplifier board was quite easy and done in a few hours, but the power supply took quite long as I paid careful attention while building it because you know, things plugged into the mains. The PSU originally put out multiple voltages for not only the Amp itself(24V) but also the Vacuum fluorescent display and other shenanigans I don't need. I threw out everything except the 24V for the amplifier and the 5V rail to power the RPI and micro-controller that I will put into the device for the 'smart' part. I still have to isolate the bottom of the Power supply and build a small shielding for it to eliminate noise as it will be sitting directly behind the amplifier part. Like I said, apart from these two PCBs I will also be putting a RPI1 and a STM32 with a LCD screen and rotary encoder into this thing to give it streaming capabilities. I will keep you up to date on the progress! submitted by /u/FloTec09 [link] [comments]

There’s been interest recently here in the land of Design Ideas (DIs) in a family of simple interface circuits for pulse width modulation (PWM) control of generic voltage regulators (both linear and switching). Members of the family rely on the regulator’s internal voltage reference and a discrete FET connected in series with the regulator’s programming voltage divider. 

PWM uses the FET as a switch to modulate the bottom resistor (R1) of the divider, so that the 0 to 100% PWM duty factor (DF) varies the time-averaged effective conductance of R1 from 0 to 100% of its nominal value.  This variation programs the regulator output from Vo = Vs (its feedback pin reference voltage) at DF = 0 to Vo = Vs(R2/R1 + 1) at DF = 100%.

Wow the engineering world with your unique design: Design Ideas Submission Guide

Some of these circuits establish a linear functionality between DF and Vo. Figure 1 is an example of that genre as described in “PWM buck regulator interface generalized design equations.”

Figure 1 PWM programs Vo linearly where Vo = Vs(R2/(R1/DF) + 1).

For others, like Figure 2’s concept designed by frequent contributor Christopher Paul and explained in “Improve PWM controller-induced ripple in voltage regulators”…it’s nonlinear…

Figure 2 PWM programs Vo nonlinearly where Vo = Vs(R2/(R1a/DF + R1b + R1c) + 1).

Note that for clarity, Figure 2 does not include many exciting details of Paul’s innovative design. See his article at the link for the whole story.

The nonlinearity problem

However, to explore the implications of Figure 2’s nonlinearity a bit further, in the example of the circuit provided in Paul’ DI:  

R1a = 2490 Ω
R1b = 2490 Ω
R1c = 4990 Ω
Vs =  0.800 V
R2 = 53600 Ω

Which, if we assume 8-bit PWM resolution, provides the response curves shown in Figure 3.

Figure 3 The 8-bit PWM setting versus DF = X/255. The left axis (blue curve) is Vo = 0.8(53600/(2490/(X/255) + 7480) + 1). The right axis (red curve) is Vo volts increment per PWM least significant bit (LSBit) increment.

Paul says of this nonlinear response: “Although the output voltage is no longer a linear function of the PWM duty cycle, a simple software-based lookup table renders this a mere inconvenience. (Yup, ‘we can fix it in software!’)”Of course, he’s absolutely right: For any chosen Vo, a corresponding DF can be easily calculated and stored in a small (256-entry) lookup table. 

However, translating from the computed DF to an integer 8-bit PWM code is a different matter. Figure 3’s increment-vs-increment red curve provides an important caveat to Paul’s otherwise accurate statement.

If the conversion from 8-bit 0 to 255 code to the 0.8 V to 5.1 V, or 4.3V Vo span, were linear, then each LSBit increment would bump Vo by a constant 15.8 mV (= 4.3 V/256). But it isn’t. 

And, as Figure 3’s red curve shows, due to the strong nonlinearity of the conversion, the 8-bit resolution criterion is exceeded for all PWM codes < 75 and Vo < 3.77 V = 74% of full scale. 

And it gets worse: For Vo values down near Vs = 0.8 V, the LSBit increment soars to 67 mV (= 4.3 V/64). This, therefore, equates to a resolution of not 8 bits, but barely 6.

The fix

Unfortunately, there’s very little any software fix can do about that. Which might make nonlinearity for some applications perhaps more than just an “inconvenience?” So what could fix it?

The nonlinearity basically arises from the fact that only a fraction (R1a) of the total R1abc resistance is modulated by PWM, as the PWM DF changes, that fraction changes, which in turn changes the rate of change of Vo versus DF. In fact, it changes this by quite a lot.

Getting to specifics, in the example of Paul’s circuit provided in his DI, we see they make the modulated resistance R1a only 25% of the total R1 resistance at DF = 100%, with this proportion increasing to 100% as DF goes to 0%. This is obviously a big change concentrated toward lower DF.

A clue to a possible (at least partial) fix is found back in the observation that the nonlinearity and resolution loss originally arose from the fact that only a small fraction (25% R1a) of the total R1abc resistance is modulated by PWM. So, perhaps a bigger R1a fraction of R1abc could recover some of the lost resolution. 

As an experiment, I changed Paul’s R1 resistor values to the following.

 R1a = 7960 Ω
R1b = 1000 Ω
R1c = 1000 Ω

This makes R1a now 80% of R1abc instead of only 25%. Figure 4 illustrates the effect on the response curves. 

Figure 4 The impact of making R1a 80% of R1abc. The left axis (blue curve) is Vo = 0.8(53600/(7960/(X/255) + 2000) + 1). The right axis (red curve) is Vo volts increment per PWM LSBit increment.

Figure 4’s blue Vo versus PWM curve is obviously still nonlinear, but significantly less so. But perhaps the more important improvement is to the red curve: Unlike the previous erosion of resolution at the left end of the curve to 67 mV per PWM LSBit to just 6 bits, Figure 3 maxes out at 21 mV, or 7.7 bits.

Is this a “fix?” Well, obviously, 7.7 bits is better than 6 bits, but it’s still not 8 bits, so resolution recovery isn’t perfect. Also, my arbitrary shuffling of  R1 ratios is almost certain to adversely impact the spectacular ripple attenuation cited in Christopher Paul’s original article. Mid-frequency loop gain may also suffer from the heavier loading on C2 and R2 imposed by the reduced R1c value. This could lead to a possible deterioration of the transient response and noise rejection. Perhaps C2 could be increased to moderate that effect.

Still, it would be fair to call it a start at a fix for nonlinearity that lay beyond the reach of software.

Stephen Woodward’s relationship with EDN’s DI column goes back quite a long way. Over 100 submissions have been accepted since his first contribution back in 1974.

Related Content

• Improve PWM controller-induced ripple in voltage regulators
• PWM buck regulator interface generalized design equations
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• Brute force mitigation of PWM Vdd and ground “saturation” errors

The post PWM nonlinearity that software can’t fix appeared first on EDN.