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КПІ ім. Ігоря Сікорського продовжує цикл зустрічей з представниками «Азову» KPI4U-1 ср, 11/12/2025 - 08:49

Nuvoton Technology announced the launch of NuMicro M5531 series microcontrollers, powerful MCUs designed to deliver advanced digital signal processing performance. Based on the Arm Cortex-M55 processor, the M5531 series runs at speeds up to 220 MHz, delivering up to 371 DMIPS of computing performance. It also features excellent noise immunity, passing 3 kV ESD HBM and 4.4 kV EFT tests, providing users with stable and high-speed system performance.

Comprehensive Security Features Designed to Meet PSA Level 2 Requirements

Recognizing the growing demand for enhanced product security, the M5531 series integrates multiple hardware-based security mechanisms to strengthen system integrity and protection. These include Arm TrustZone, Secure Boot, cryptographic engines (AES-256, ECC-571, RSA-4096, SHA-512, HMAC-512), Key Store, Key Derivation Function, True Random Number Generator (TRNG), eXecute-Only-Memory, One-Time Programmable Memory (OTP), and tamper detection pins.

In terms of power efficiency, the M5531 series delivers impressive performance with a dynamic power consumption as low as 94.5 µA/MHz. It also offers multiple low-power peripherals such as LPSRAM, LPPDMA, LPTimer, and 12-bit LPADC, allowing the system to maintain essential functions in low-power modes.

Application Fields

The M5531 series is suitable for a wide range of industrial, consumer, and connected products, including:
 Industrial IoT (e.g., industrial gateways, communication modules)
 Industrial automation (e.g., PLC protocol converters)
 Smart building systems (e.g., fire alarm systems, LED advertising display)
 HMI applications (e.g., smart thermostats)
 Sensor fusion (e.g., environmental data collectors)

The post Nuvoton Technology Launches NuMicro M5531 Series Microcontrollers appeared first on ELE Times.

submitted by /u/BlownUpCapacitor [link] [comments]

submitted by /u/cstrlib [link] [comments]

Hey everyone! Hope the UK timezone rule for the WBW still holds true haha. Almost exactly three years back I posted my beginner hobbyist bench on the sub and got a ton of kind and helpful feedback from y'all. This new album is a present-day update three years later, after many changes and acquisitions during and for my projects. Overall I learned a ton about what I actually use the most and tried to make it all zero nuisance to get to. If it takes too many steps to get out or get ready it's no good. Some of your predictions back then also came true! I did lob a 3D printer onto that side table and got into CAD and printing in a major way, which I now use in a lot of projects for case parts, mechanical bits, etc. I wound up building a few robots out of a mix of alu extrusion beams and 3D-printed parts. This is why you see a lot more tools now dedicated to mechanics - measuring, fastening, glueing, cutting, deburring, etc. - to complement the electronics toolset. I ended up getting a low-end benchtop meter after I got tired of getting out and throwing around my $20 handheld. Much happier with a permanent fixture. Dremel (well, Proxxon) on a steel cable retractor, permanently plugged in. Actually best idea ever! My circumstances don't really allow for a ton of dust and dirt creation, but for a quick cut or a grind/polish this is so convenient to grab down, and managable. I got my hands on two airline galley trolleys with pull-out tables. In my limited space this is perfect for additional on-demand benchtop space, and it's where I much of my growing electronics stock and some simple hardware. Shoutout to that Omnifixo. The hype for once is true. I've never been happier soldering and use it daily. It's of course hardly ever this presentable. I just had some time off work and did a big tidying pass that reminded me of the older beauty shots. submitted by /u/NewbieSone [link] [comments]

TDK Corp. adds a new single-phase series of DIN-rail-mount power supplies to the TDK-Lambda range of products for industrial and automation applications. The cost-effective  D1SE entry-range series provides an AC and DC input and is rated for continuous operation at 120 W, 240 W or 480 W with a 24-V output. These power supplies deliver an efficiency of up to 95.1%, reducing energy consumption and internal losses, which lower the internal component temperatures and improve long-term product reliability.

(Source: TDK Corp.)

Thanks to the push-in wire terminations, the D1SE series can be quickly mounted, reducing installation time in a variety of control cabinets, machinery, and industrial production systems. In addition to a conventional 100 to 240-VAC nominal input, the D1SE is safety certified for operation from a 93 to 300-VDC supply. Designed to meet growing customer demand, the DC input addresses applications where the energy supply is coming from a common DC bus voltage or a battery.

The 120-W rated model can deliver a boost power of 156 W for 80 seconds; the 240-W rated model offers a boost of 312 W for 10 seconds; and the 480-W rated model provides a boost of 552 W for an extended 200 seconds. The 24-V output can be adjusted from 22.5 V to 29 V to allow compensation for cable drops, redundancy modules, or setting to non-standard output voltages.

All three power supplies are available with or without a DC-OK contact. For applications in challenging environments, a printed-circuit-board coating option is available, and all models feature a high-quality electrolytic capacitor which extends lifetime, according to TDK.

The DIN-rail-mount power supplies are housed in a rugged metal enclosure with a width of 38 mm for the 120-W models, 44 mm for the 240 W, and 60 mm for the 480 W. The narrow design saves space on the DIN rail for other components, the company said.

Other key specs include input-to-output isolation of 5,000 VDC, input-to-ground at 3,100 VDC, and output-to-ground at 750 VDC. The D1SE models are convection-cooled and rated for operation in the -25°C to 70°C ambient temperature range, with derating above 55°C.

Series certifications include IEC/EN/UL/CSA 61010-1, 61010-2-201, 62368-1 (Ed.3), and IS 13252-1 standards. The power supplies also are CE and UKCA marked to the Low Voltage, EMC, and RoHS Directives, and meet EN 55011-B and CISPR11-B radiated and conducted emissions.

The series also complies with EN 61000-3-2 (Class A) harmonic currents and IEC/EN 61000-6-2 immunity standards. The power supplies come with a three-year warranty.

The post Compact DIN-rail power supplies deliver high efficiency appeared first on EDN.

ABLIC Inc. upgrades its CLEAN-Boost energy-harvesting technology for the U.S. and EU markets. The battery-less drip-level water leak sensor now offers a communication range that is approximately 2× that of its predecessor and an expanded operating temperature range of up to 85°C from 60°C. 

ABLIC said it first launched the CLEAN-Boost energy harvesting technology in 2019 to generate, store, boost, and transform microwatt-level energy into electricity for wireless data transmission. Since that launch, the Japan-market model earned positive evaluations from over 80 customers, and given increased inquiries from U.S. and European customers, the company  obtained the necessary certifications from the U.S. Federal Communications Commission and the EU’s Conformité Européenne, confirming compliance with key standards.

CLEAN-Boost can be used in any facility where a water leak poses a potential risk. It uses microwatt energy sources to generate electricity from leaking water and transmits water signals wirelessly. The latest enhancements enable the sensor’s use in a wider range of applications and high-temperature environments, the company said.

Applications where addressing water leaks is critical include automotive parts factories with stamping processes, chemical and pharmaceutical plants, and food processing facilities as well as in aging buildings where pipes may have weakened or in high-temperature operations such as data centers and server rooms.

(Source: ABLIC Inc.)

ABLIC claims the water leak sensor is the industry’s first sensor capable of detecting minute drops of water. It can detect as little as three drops of water (150 μl minimum). In addition, operating without an external power source eliminates the need for major installation work or battery replacement, making it suited for retrofitting into existing infrastructures.

The water leak sensor also helps reduce environmental impact by eliminating the need to replace or dispose of a battery. For example, the sensor has been certified as a MinebeaMitsumi Group “Green Product” for outstanding contribution to the environment.

ABLIC’s CLEAN-Boost technology works by capturing and amplifying microwatt-level environmental energy previously considered too minimal to use. It combines energy storage and boosting components, designed for ultra-low power consumption. The boost circuit operates at 0.35 V for the efficient use of 1 μW of input power. It incorporates a low-power data transmission method that optimizes the timing between power generation and signal transmission, ensuring maximum efficiency and stable operation even under extremely limited power.

(Source: ABLIC Inc.)

The sensor features simple add-on installation for easy integration and sends wireless alerts to safeguard against catastrophic water damage.

The sensor technology is available as a wireless tag (134 × 10 × 18 mm with the main body measuring 65 × 10 × 18 mm), or sensor ribbons (sensor ribbon 0.5 m, sensor ribbon 2.0 m, and sensor ribbon 5.0 m), measuring 700 ×13 × 8 mm, 2200 × 13 × 8 mm, and 5200 × 13 × 8 mm, respectively. They can be connected up to 15 m.

The post ABLIC upgrades battery-less water leak detection sensor appeared first on EDN.

My first time designing a microcontroller board. I wanted to look into getting it assembled by overseas manufacturers but they wanted to charge me over $100 and take over a month to assemble and I said nah I’ll do it myself. I got a convection toaster oven off of facebook marketplace for like $10 and drilled a small hole in the back for a thermocouple which is connected to an ESP32 dev board. I didn’t create a controller which is something I might do eventually but for the time being I had to manually adjust the oven temperature to try and match the reflow curve as best as I could. You can see in the third picture the red line is the expected reflow curve from the solder paste datasheet and the blue line was the real time temperature readings. I was using that graph in real time to make my adjustments. Placing all the components took me about an hour and I had practiced following the reflow curve twice lol but the end result was a really nice looking PCB! Not only that, but my PC was able to detect the board as a USB DFU device when I pressed the boot switch while plugging the cable into the board! All in all very happy with how this turned out and I think I did pretty well for my first time doing something like this! TL;DR Reflowed a board for the first time using a convection toaster oven that I manually controlled and everything worked out :) submitted by /u/jrabr [link] [comments]

First 2 pictures are corner to corner and last is just bent in half. Found on ali. submitted by /u/Whyjustwhydothat [link] [comments]

“Facts are stubborn things” (John Adams, et al).

I added two 50-ohm outputs to the schematic of my published voltage-to-frequency converter (VFC) circuit (Figure 1). Then, I designed a PCB, purchased the (mostly) surface-mount components, loaded and re-flow soldered them onto the PCB, and then tested the design.

Figure 1 VFC design that operates from 100 kHz to beyond 100 MHz with a single 5.25-V supply, providing square wave outputs at 1/2 and 1/4 the main oscillator frequency.  

The hardware implementation of the circuit can be seen in Figure 2.

Figure 2  The hardware implementation of the 100MHz VFC was created in order to root out the facts that can only be obtained after it was built.

My objective was to get the facts about the operation of the circuit. 

Theory and simulation are important, but the facts are known only after the circuit is built and tested. That is when the unintended/unexpected consequences are seen.

The circuit mostly performed as expected, but there were some significant issues that had to be addressed in order to get the circuit performing well.

Sensitivity of the v-to-f

My first concern was the high sensitivity of the circuit to minute changes in the input voltage.  The sensitivity is 100 MHz per 5 volts, i.e., 20 MHz per volt. That means a 1-mV change on the input results in a 20-kHz change in the output frequency!

So, how do you supply an input voltage that is almost totally devoid of noise and/or ripple, which will cause jitter on the oscillator signal? To deal with this problem, I used a battery supply, four alkaline batteries in series, connected to a 10-turn, 100-kΩ potentiometer to drive the input of the circuit with about 0 to 6 V. This worked quite well. I added a 10 kΩ resistor in series with the non-inverting input of U1 for protection against overvoltage.

Problems and fixes

The first unexpected problem was that the NE555 timer did not provide sufficient drive to the voltage inverter circuit and the voltage doubler circuit. This one is on me; I didn’t look carefully at the datasheet, which says it can supply a lot of output current, but at high current, the output voltage drops so much that the inverter and the doubler circuits don’t provide enough output voltage. And the LTspice model I used for simulation was a very unrealistic model. I recommend that it not be used!

I fixed this by using a 74HC14 Schmitt trigger chip to replace the NE555 timer chip. The 74HC14 provides plenty of current and voltage to drive the two circuits. I implemented the 74HC14 circuitry as an outboard attachment to the main PCB. 

I changed the output of the voltage doubler circuit to a regulated 6 V (R16 changed to 274 Ω and R18 to 3.74 kΩ, and D8, D9 changed to SD103). This allows U1 to operate with an input voltage of up to about 5.9 V. Also, I substituted a TLV9162 dual op-amp for U1/U2 because the cost of the TLV9162 is much less than that of the LT1797. 

With the correct voltages supplied to U1/U2, I began testing the circuit, and I found that the oscillator would hang at a frequency of about 2 MHz. This was caused by the paralleled Schmitt trigger inverters. One inverter would switch before the other one, which would then sink the current from the inverter that had switched to the HIGH output state, and the oscillator would stop functioning. Paralleling inverters, which are driven by a relatively slowly falling (or rising) input signal, is definitely not a viable idea!

To fix the problem, I removed U4 from the circuit and put a 22-Ω resistor in series with the output of inverter U3 to lessen the current load on it, and the oscillator operated as expected.

I made some changes to the current-to-voltage converter circuit to provide more adjustment range and to use the optimum values for the 5-V supply. I changed R8 to 3.09 kΩ, potentiometer R9 to 1 kΩ, and R13 to 2.5 kΩ.

Adjustments

There are two adjustments provided: R9 is an adjustment for the current-to-voltage converter U2, and R11 is an offset current adjustment. 

I adjusted R9 to set the oscillator frequency to 100 MHz with the input voltage set to 5.00 V, and then adjusted R11 at 2 MHz.

The percent error of the circuit increases at the lower frequencies; possibly due to diode leakage currents, or nonlinear behavior of the frequency to voltage converter consisting of D2 – D4 and C8 – C11?

Test results

With the noted changes implemented, I began testing the VFC. The problem of jitter on the output signal was apparent, especially at the lower frequencies. 

I realized that ripple and noise on the 5-V supply would cause jitter on the output signal. As noted on the schematic, the oscillator frequency is a function of the supply voltage.

To avoid this problem, I once again opted to use batteries to provide the supply voltage. I used six alkaline batteries to supply about +9 V and regulated the voltage down to +5 V with an LM317T regulator and a few other components. 

This setup achieves about the minimum ripple and noise on the supply and the minimum oscillator jitter. The remaining possible sources of noise/jitter are the switching supplies for U1, the feedback voltage to U1, and the switching on and off of the counters and the inverters, which can cause noise on the +5-V supply.

The frequency versus input voltage plot is not as linear as expected, but it is pretty good over a wide range of input voltage from 50 mV to 5.00 V for a corresponding frequency range of 1.07 MHz to 103.0 MHz (Figure 3 and Figure 4). The percent error versus frequency is shown in Figure 5.

Figure 3 The frequency from 1.07 MHz to 103.0 MHz versus input voltage from 50 mV to 5.00 V.

Figure 4 The frequency (up to 2 MHz) versus input voltage when Vin < 0.1 V.

Figure 5 The percent error versus frequency.

Waveforms

Some waveforms are shown in Figure 6, Figure 7, Figure 8, and Figure 9. Most are from the divide-by-2 output because it is more visually interesting than the 3.4-ns output from the oscillator (multiply the divide-by-2 frequency by 2 to get the oscillator frequency). 

The input voltage ranges from 10 mV to 5 V to produce the 200 kHz to 100 MHz oscillator/inverter output.

Figure 6 Oscilloscope waveform with a divide-by-two output at 100 kHz.

Figure 7 Oscilloscope waveform with a divide-by-two output at 500 kHz.

Figure 8 Oscilloscope waveform with a divide-by-two output at 5 MHz.

Figure 9 Oscilloscope waveform with a divide-by-two output at 50 MHz.

Figure 10 displays the output of the oscillator/inverter at 100 MHz.  Figure 11 shows the 3.4 ns oscillator/inverter output pulse. 

Figure 10 Oscilloscope waveform with the oscillator output at 100 MHz.

Figure 11 Oscilloscope waveform with a 3.4-ns oscillator pulse.

The facts

So, here are the facts. 

The two inverters in parallel did not work in this application. This was fixed by eliminating one of them and putting a larger resistor in series with the output of the remaining one to reduce the current load on it.

The high sensitivity of the circuit to the input voltage presents a challenge in practice. Generating a sufficiently quiet input voltage is difficult.

Battery operation provides some help, but this presents its own challenges in practice. Noise on the 5-V supply is a related problem. The supply for the second divide-by-two circuit, U7, must be tightly regulated and extremely free of noise and ripple to minimize jitter on the oscillator signal.

And, as noted above, some changes in the values of several components were necessary to get acceptable operation.

Finally, more accurate voltage-versus-frequency operation at lower frequencies will require more careful engineering, if desired. I leave this to the user to work this out, if necessary. 

At this point, I am satisfied with the circuit as it is (I feel that it is time to take a break!).

Some suggestions for improved results

The circuit is compromised by the challenge to make it work with a single 5-V supply. It would be less challenging if separate, well-regulated, well-filtered supplies were used for U1/U2, for example, a 14 V regulated down to 11 V for the positive supply, and a negative 5 V regulated down to -2.5 V (use linear regulators for both supplies!) 

The input could then range from 0 to 10 V, which would reduce the input sensitivity by a factor of two and make it easier to design quieter supplies for the input amplifier and current-to-voltage circuits, U1/U2.

At the lower frequencies, some investigation should be done to expose the causes of the nonlinearity in that frequency range, and to indicate changes that would improve the circuit operation.

Another option would be to split the operation into two ranges, such as 100 kHz to 1 MHz and 1 MHz to 100 MHz.

Final fact

The operation of the circuit is pretty impressive when the circuit is modified as suggested. I think actualizing an oscillator that provides an output from 200 kHz to 113 MHz is quite a remarkable result. Thanks to the late Jim Williams [2] and to the lively Stephen Woodward [3] for leading the way to the implementation of this circuit!

Jim McLucas retired from Hewlett-Packard Company after 30 years working in production engineering and on the design and test of analog and digital circuits.

References/Related Content

1. A simulated 100-MHz VFC
2. 1-Hz to 100-MHz VFC features 160-dB dynamic range
3. 100-MHz VFC with TBH current pump
4. Take-Back-Half precision diode charge pump

The post My 100-MHz VFC – the hardware version appeared first on EDN.

III–V Epi Ltd of Glasgow, Scotland, UK — which provides a molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) service for custom compound semiconductor wafer design, manufacturing, test and characterization — says that its chief technical officer professor Richard Hogg is chairing two sessions at PCSEL 2025 (the International Workshop on PCSELs) held at the University of Glasgow on 10–12 November. This includes the Keynote Session ‘Progress of PCSELs’ from PCSEL research pioneer Susumu Noda, professor of Electronic Science and Engineering at Kyoto University in Japan...

STMicroelectronics has revealed the ISM6HG256X, a tiny three-in-one motion sensor for data-hungry industrial IoT applications, serving as an additional catalyst for edge AI advancement. This smart, highly accurate IMU sensor uniquely combines simultaneous detection of low-g (±16g) and high-g (±256g) accelerations with a high performance and stable gyroscope within a single compact package, ensuring no critical event—from subtle motion or vibrations to severe shocks—is ever missed.

The ISM6HG256X addresses the growing demand for reliable, high-performance sensors in industrial IoT applications such as asset tracking, worker safety wearables, condition monitoring, robotics, factory automation, and black box event recording. By integrating accelerometer with dual full-scale ranges, it eliminates the need for multiple sensors, simplifying system design and reducing overall complexity. Its embedded edge processing and self-configurability support real-time event detection and context-adaptive sensing, which are essential for long lasting asset tracking sensor nodes, wearable safety devices, continuous industrial equipment monitoring, and automated factory systems.

“Traditional solutions require multiple sensors to cover low and high acceleration ranges, increasing system complexity, power consumption, and cost. The ISM6HG256X addresses these challenges by providing a single, highly integrated sensor,” said Simone Ferri, APMS Group VP & MEMS Sub-Group GM, STMicroelectronics. “These new sensing dimensions, made possible also in harsh environment, combined with machine-learning running inside the IMU sensor itself, allows to quickly recognize, track and classify motion, activities and events while using very little power, helping businesses make smart, data-driven decisions as they move toward digital transformation.”

Technical information

The ISM6HG256X contains the unique machine-learning core (MLC) and finite state machine (FSM), together with adaptive self-configuration (ASC) and sensor fusion low power (SFLP). These features bring edge AI directly into the sensor to autonomously classify detected events, ensuring real-time, low-latency performance and ultra-low system power consumption. This embedded technology can reconstruct signal dynamics to provide high-fidelity motion tracking. Thanks to the embedded SFLP algorithm, also 3D orientation tracking is possible with just few µA of current consumption. 

ST’s new X-NUCLEO-IKS5A1 industrial expansion board with MEMS Studio design environment and extensive software libraries, X-CUBE-MEMS1, are available to assist developers, helping implement functions including high-g and low-g fusion, sensor fusion, context awareness, asset tracking, and calibration.

The ISM6HG256X is available now, in a 2.5mm x 3mm surface-mount package built to withstand harsh industrial environments from -40°C to 105°C. Pricing starts at $4.27 for orders of 1000 pieces, from the eSTore and through distributors.

The ISM6HG256X is part of ST’s longevity program, which ensures long-term availability of critical components for at least 10 years to support customers’ industrial product ranges.

The post STMicroelectronics empowers data-hungry industrial transformation with unique dual-range motion sensor appeared first on ELE Times.

Wolfspeed Inc of Durham, NC, USA — which makes silicon carbide (SiC) materials and power semiconductor devices — is collaborating with renewable energy solutions firm Hopewind of Shenzhen City (one of the largest wind power converter suppliers in China). Together, the two firms will advance the development of the next generation of wind power solutions by integrating Wolfspeed’s 2.3kV LM Pack Module into Hopewind’s highly modular and lightweight 950Vac Wind Power Converter...

🚀 Підсумкова науково-практична конференція Міжнародного конкурсу студентських наукових робіт зі штучного інтелекту в КПІ ім. Ігоря Сікорського kpi вт, 11/11/2025 - 10:00

Іван Пишнограєв. Застосовує ШІ для прийняття рішень Інформація КП вт, 11/11/2025 - 10:00

In industrial applications using digital-to-analog converters (DACs), programmable logic controllers (PLCs) set an analog output voltage to control actuators, motors, and valves. PLCs can also regulate manufacturing parameters such as temperature, pressure, and flow.

In these environments, the DAC output may require overvoltage protection from accidental shorts to higher-voltage power supplies and other sustained high-voltage miswired connections. You can protect precision DAC outputs in two different ways, depending on whether the DAC output buffer has an external feedback pin.

Overvoltage damage

There are two potential consequences should an accidental sustained overvoltage event occur at the DAC output.

First, if the DAC output can drive an unsustainable current limit, then damage may occur as the output buffer drives an excess of current. This current limit may also occur if the output voltage is shorted to ground or to another voltage within the supply range of the DAC.

Second, electrostatic discharge (ESD) diodes latched to the supply and ground can source and sink current during sustained overvoltage events, as shown in Figure 1 and Figure 2. In many DACs, a pair of internal ESD diodes that shunt any momentary ESD current away from the device can help protect the output pin. In Figure 1, a large positive voltage causes an overvoltage event in the output and forward-biases the positive AVDD ESD diode. The VOUT pin sinks current from the overvoltage event into the positive supply.

Figure 1 Current is shunted to positive supply during a positive overvoltage event. Source: Texas Instruments

In Figure 2, the negative overvoltage sources current from the negative supply through the AVSS ESD diode to VOUT.

Figure 2 Current is shunted to positive supply during a negative overvoltage event. Source: Texas Instruments

In Figure 1 and Figure 2, internal ESD diodes are not designed to sink or source current associated with a sustained overvoltage event, which will typically damage the ESD diodes and voltage output. Any protection should limit this current during an overvoltage event.

Overvoltage protection

While two basic components will protect precision DAC outputs from an overvoltage event, the protection topology for the DAC depends on the internal or external feedback connection for the DAC output buffer.

If the DAC output does not have an external voltage feedback pin, you can set up protection as a basic buffer using an operational amplifier (op amp) and a current protection device at its output. If the DAC has an external voltage feedback pin, then you would place the current protection device at the output of the DAC, with the op amp driving the feedback sense pin.

Let’s explore both topologies.

Figure 3 shows protection for a DAC without a feedback sense pin, with the op amp set up as a unity gain buffer. Inside the op amp feedback, an eFuse opens the circuit if the op amp output current exceeds a set level.

Figure 3 Output protection for a DAC works without a feedback pin. Source: Texas Instruments

Again, if the output terminal voltage is within the supplies of the op amp, the output current comes from the short-circuit current limit. An output terminal set beyond the supplies of the op amp, as in a positive or negative overvoltage, will cause the supply rails to source or sink additional current, as previously shown in Figure 1 and Figure 2.

Because the output terminal connects to the op amp’s negative input, the op amp input must have some sort of overvoltage protection. For this protection circuit, an op amp with internal overvoltage protection that extends far beyond the op amp supply voltage is selected. When using a different op amp, series resistance that limits the input current can help protect the inputs.

The circuit shown in Figure 3 will also work for a precision DAC with a feedback sense pin. The DAC feedback sense pin would simply connect to the DAC VOUT pin, using the same protection buffer circuit. If you want to use the DAC feedback to reduce errors from long output and feedback sense wire resistances, you need to use a different topology for the protection circuit.

If the DAC has an external feedback sense pin, changing the protection preserves the sense connection. In Figure 4, the eFuse connects directly to the DAC output. The eFuse opens if the DAC output current exceeds a set level. Here, the op amp acts as a unity gain buffer to drive the DAC sense feedback pin.

Figure 4 This output protection for a DAC works with a feedback pin. Source: Texas Instruments

In both topologies, shown in Figure 3 and Figure 4, the two protection devices have the same requirements. For the eFuse, the break current must be lower than the current level that might damage the device it’s protecting. For the op amp, input protection is required, as the output overvoltage may significantly exceed the rail voltage. In operation, the offset voltage must be lower than the intended error, and the bandwidth must be high enough to satisfy the system requirements.

Overvoltage protection component selection

To help you select the required components, here are the system requirements for operation and protection:

• Supply range: ±15 V
• Sustained overvoltage protection: ±32 V
• Current at sustained overvoltage: approximately 30 mA
• Output protection should introduce as little error as possible, based on offset or bandwidth

The primary criteria for op amp selection were overvoltage protection of the inputs. For instance, the super-beta inputs of the OPA206 precision op amp have an integrated input overvoltage protection that extends up to ±40 V beyond the op amp supply voltage. Figure 5 shows the input bias current relative to the input common-mode voltage powering OPA206 with ±15 V supplies. Within the ±32 V range of overvoltage protection, the input bias current stays below ±5 mA of input current.

Figure 5 Input bias current for the OPA206 is shown versus the input common-mode voltage. Source: Texas Instruments

The OPA206 offset voltage is very low (typically ±4 µV at 25°C and ±55 µV from –40°C to 125°C) and the buffer contributes little error to the DAC output. When using a different op amp without integrated input overvoltage protection, adding series resistance at the inputs will limit the input current.

The TPS2661 eFuse was originally intended as a current-loop protector with input and output miswiring protection. If its output voltage exceeds the rail supplies, TPS2661 detects miswiring and cuts off the current path, restoring the current path when the output overvoltage returns below the supply.

If the output current exceeds TPS2661’s 32-mA current-limit protection, the device breaks the connection and retests the current path for 100 ms periodically every 800 ms. The equivalent resistance of the device is a maximum 12.5 Ω, which enables a high-current transmission output without large voltage headroom and footroom loss at the output.

Beyond the op amp and eFuse protection, applying an optional transient voltage suppression (TVS) diode will provide additional surge protection as long as the chosen breakdown voltage is higher than any sustained overvoltage. If the breakdown voltage is less than the sustained overvoltage, then an overvoltage can damage the TVS diode. In this circuit, the expected sustained overvoltage is ±32 V, with an optional TVS3301 device that has a bidirectional 33-V breakdown for surge protection.

Another TVS3301 added to the ±15-V supplies is an additional option. An overvoltage on the terminal will direct any fault current into the power supplies. If the supply cannot sink the current or is not fast enough to respond to the overvoltage, then the TVS diode absorbs excess current as the overvoltage occurs.

Constructed circuit: Precision DAC without a feedback sense pin

You can build and test the overvoltage protection buffer from Figure 3 with the DAC81416-08 evaluation module (EVM). This multichannel DAC doesn’t have an external feedback sense pin. Figure 6 shows the constructed protection buffer tested on one of the DAC channels.

Figure 6 The constructed overvoltage protection circuit employs the DAC81416-08 evaluation module. Source: Texas Instruments

Ramping the output of DAC from –10 V to 10 V drives the buffer input. Figure 7 shows that the measured offset of the buffer is less than 10 µV over the full range.

Figure 7 Protection buffer output offset error is shown versus buffer input voltage. Source: Texas Instruments

Connecting the output to a variable supply tests the output overvoltage connection, driving the output voltage and then recording the current at the output. The measurement starts at –32 V, increases to +32 V, then changes back from +32 V down to –32 V. Figure 8 shows the output current set to overvoltage and its recovery from overvoltage.

Figure 8 Protection buffer output current is shown versus buffer output overvoltage. Source: Texas Instruments

The measurements show hysteresis in both the positive and negative overvoltage of the protection buffer that comes from extra voltage across the series resistor at the output of the TPS26611. During normal operation (without an overvoltage), the TPS26611 current path turns off when the output rises and is driven above 17.2 V, at which point the remaining output current comes from the overvoltage of the OPA206 input. As the output voltage decreases, the TPS26611 current path conducts current again when the output drops below 15 V.

When driving the output to a negative overvoltage, the current path turns off at –17.5 V and turns on again when the output returns above –15 V.

Constructed circuit: Protection for a DAC with output feedback

Like the previous circuit, you can test the overvoltage protection from Figure 4. This test attaches an overvoltage protection buffer to the output of a DAC with an external feedback sense pin. The DAC8760 EVM tests for an output overvoltage event. As shown in Figure 9, a 1-kΩ resistor placed between VOUT and +VSENSE prevents the output buffer feedback loop of the DAC from breaking if the feedback sense signal is cut.

Figure 9 This constructed overvoltage protection circuit is used with the DAC8760 evaluation module. Source: Texas Instruments

Ramping the output of the DAC from –10 V to +10 V drives the feedback buffer input. Shown in Figure 10, the offset of the feedback to +VSENSE is again <10 μV over the full range.

Figure 10 Feedback buffer offset error is shown versus buffer input voltage. Source: Texas Instruments

The DAC is again set to 0 V, with the output connected to a variable supply to check the output current against output overvoltage. Figure 11 shows the output current as the output voltage increases from –32 V to +32 V and decreases to –32 V.

Figure 11 Protection buffer output current is shown versus buffer output overvoltage. Source: Texas Instruments

As before, there is current path hysteresis. The TPS26611 current path shuts off when the output goes above 16.5 V and turns on when the output returns to about 15 V. For the negative overvoltage, the current path turns off when the output is below –16.8 V and turns on again when the output returns above –15 V.

Two overvoltage protection topologies

Industrial control applications for analog outputs require specialized protection from harsh conditions. This article presented two topologies for precision DAC protection against sustained overvoltage events:

• DAC without external feedback: Protecting the output from an overvoltage by using an op amp buffer with an eFuse in the op amp output.
• DAC with external feedback: Protecting the output from overvoltage by using an eFuse to limit the DAC output current and with an op amp acting as a unity gain buffer for sense feedback.

In both cases, the tested circuits show a limited offset error (<10 µV) through the range of operation (±10-V output) and protection from sustained overvoltage of ±32 V.

Joseph Wu is applications engineer for digital-to-analog converters (DACs) at Texas Instruments.

 

 

Art Kay is applications engineer for precision signal conditioning products at Texas Instruments.

 

 

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