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Trailing-edge dimmers offer smoother, quieter control for modern lighting systems—but their inner workings often remain overlooked. This post sheds light on the circuitry behind the silence. Sometimes, the most elegant engineering hides in the fade, where silence is not a flaw but a feature.

Let’s get started.

Dimmers serve as an effective interface for controlling energy-efficient lighting systems. And dimming methodologies are broadly categorized into forward-phase dimming (leading-edge), reverse-phase dimming (trailing-edge), and four-wire dimming, commonly referred to as 0–10 V analog dimming.

This post specifically examines reverse-phase dimming, also known as trailing-edge dimming, which is particularly well-suited for electronic low-voltage (ELV) transformers and modern LED drivers. Its smoother voltage waveform and inherently lower electromagnetic interference (EMI) make it ideal for applications requiring silent operation and compatibility with capacitive loads.

Leading and trailing edge dimming

In a leading-edge dimmer—also known as a triac dimmer or incandescent dimmer—the electrical current (sinusoidal signal) is interrupted at the beginning of the AC input waveform, immediately after the zero crossing. This dimming method is traditionally used with incandescent lamps or magnetic low-voltage transformers.

On the other hand, a trailing-edge dimmer interrupts the current at the end of the AC input waveform, just before the zero crossing (Figure 1). This technique is better suited for electronic drivers or low-voltage transformers with capacitive loads.

Figure 1 In trailing-edge dimming waveform, conduction begins mid-cycle, and current is interrupted before zero crossing to suit capacitive loads. Source: Author

In a nutshell, a trailing-edge dimmer is an electrical device used to adjust the brightness of lights in a room or space. It operates by reducing the voltage supplied to the light source, resulting in a softer, dimmer glow.

Unlike leading-edge dimmers—which cut the voltage at the beginning of each AC waveform—trailing-edge dimmers reduce the voltage at the end of the waveform. This “trailing edge” approach enables smoother, more precise dimming, especially at lower brightness levels.

Trailing-edge dimmers are particularly well-suited for LED lighting. They tend to be more efficient, generate less heat, and offer better compatibility with modern electronic drivers. The result is a quieter, flicker-free dimming experience that feels more natural to the eye.

Figure 2 The popular DimEzy brand for trailing-edge rotary dimmers embodies compact engineering optimized for retrofit installations. Source: LiquidLEDs

It’s important to note that most mains-powered LED bulbs are not dimmable. Even among those labeled as dimmable, compatibility with dimmer types can vary. Many require dedicated trailing-edge dimmers to function correctly; using the wrong dimmer may lead to flickering, limited dimming range, or even premature failure. Always check the bulb’s specifications and pair it with a suitable dimmer for reliable, smooth performance.

Moreover, since LED bulbs and dimmers are mains-operated, even minor mishandling can lead to electric shock or fire hazards. Always choose compatible components and follow safety guidelines.

Trailing-edge dimmer design: The starting point

Building a trailing edge dimmer is not trivial; but it’s far from overcomplicated. Below is a conceptual block diagram for those poised at the starting line.

Figure 3 A conceptual block diagram highlights the key functional units coordinating trailing-edge dimming. Source: Author

From the block diagram above, several distinct functional stages interact with each other to perform the overall dimming functionality. In a trailing-edge dimmer circuit, the power supply delivers a stable low-voltage DC source to power control and switching stages. The zero-crossing (ZC) detector pinpoints the exact moment the AC waveform crosses zero volts, providing a timing reference for phase control.

Based on this, the timing control block calculates a delay to determine when to switch off the load during each half-cycle, shaping the trailing edge of the waveform. This delayed signal is then fed to the gate driver, which conditions it to reliably switch the power MOSFETs, the primary switching elements that interrupt current partway through each cycle, enabling smooth dimming with minimal noise and flicker.

So, for your trailing-edge dimmer, the selection of components involves careful consideration of their roles in the dimming process.

• Power supply (DC): This supply will power the control circuitry, including the digital logic and gate drivers. Its voltage and current rating must be sufficient to reliably operate these components, especially under varying load conditions.
• Zero-crossing (ZC) detector: This detector is fundamental for timing the dimming cycle. It senses when the AC waveform crosses zero, providing a synchronization point. The ZC detector should be fast and accurate to ensure precise dimming.
• Timing control: This element, often integrated with digital logic, dictates the duration for which the power MOSFET remains on during each AC half-cycle. For trailing-edge dimming, the gate pulse is enabled at the ZC signal and disabled after a specific ON-time pulse width.
• Digital logic: This is the brain of the dimmer, interpreting user input—for instance, from a potentiometer or button—and controlling the timing logic. It might involve simple logic gates or a microcontroller. One document mentions a triple 3-input NOR gate for control, indicating the use of basic digital logic.
• Gate drivers: Gate drivers are essential for efficiently switching power. They provide the necessary current and voltage levels to turn the MOSFETs on and off quickly, minimizing switching losses and heat generation. Proper selection ensures a clean gate drive signal.
• Power MOSFETs: The power MOSFET acts as the main switching element, controlling the power delivered to the load. It must be chosen based on the load’s voltage and current requirements, with low on-state resistance (Rdson) for efficiency and adequate heat dissipation capabilities. For AC dimming, devices capable of handling the AC voltage and current, such as specific MOSFETs or IGBTS designed for phase control, are necessary.

Recall that a trailing-edge dimmer operates using transistor switches that begin conducting at the start of each half sine wave. These switches remain active for a defined conduction angle, after which they turn off, effectively truncating the AC waveform delivered to the load.

This approach results in smoother current transitions. The electronic load benefits from the gentle rise of the sine wave, and once the switch turns off, any residual energy stored in inductive or capacitive components naturally dissipates to zero. This behavior contributes to quieter operation and improved compatibility with sensitive electronic loads.

Up next is the practical schematic of a trailing edge phase control rotary wall dimmer designed without a microcontroller and originally introduced by STMicroelectronics over a decade ago.

Although this elegant concept now calls for a few updates—mainly due to the unavailability of certain key components (fortunately, drop-in replacements exist)—it remains an invaluable design reference, at least to me. I could not have expressed it better myself, so here is the link to its full documentation.

Figure 4 Rotary wall dimmer circuit employs reverse-phase control to regulate mixed lighting loads. Source: STMicroelectronics

Happy dimming

In summary, there is not much more to add regarding trailing-edge dimmers for now. However, it’s worth noting that these dimmers can also be built using a microcontroller, which is especially useful for smart lighting systems. Compared to specialized dimmer ICs, microcontrollers provide more freedom to create custom dimming profiles, incorporate user interfaces, and connect with smart home technologies like Wi-Fi or Bluetooth.

That is all for now. But don’t let the dimming stop here.

Dive deeper into the fascinating world of trailing-edge dimmers. Experiment with different component combinations, explore their impact on dimming performance, and share your discoveries with us.

What will you create next? Let’s know your thoughts or any challenges you encounter as you build your own dimming solutions. Your insights could light the way for others.

Happy dimming!

T. K. Hareendran is a self-taught electronics enthusiast with a strong passion for innovative circuit design and hands-on technology. He develops both experimental and practical electronic projects, documenting and sharing his work to support fellow tinkerers and learners. Beyond the workbench, he dedicates time to technical writing and hardware evaluations to contribute meaningfully to the maker community.

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• DC/DC Converter Considerations for Smart Lighting Designs

The post Behind the curve: A practical look at trailing-edge dimmers appeared first on EDN.

Infineon Technologies AG claims the industry’s first radiation-hardened (rad-hard) buck controller with an integrated gate drive. The RIC70847 buck controller targets point-of-load power rails in commercial space systems and other extreme environments. Applications include distributed satellite power systems and digital processing payloads, including FPGA and ASIC systems. 
 

(Source: Infineon Technologies AG)

The RIC70847 comprises a 17.1-V buck controller with a 5-V (output) half-bridge gate drive, suited for applications with a power input range of 4.75 V to 15 V and power output range of 0.6 V to 5.25 V. The device meets the MIL spec temperature range of -55°C to 125°C and applications that require a total ionizing dose rating of up to 100 krad (Si) and single event effects characterized up to a linear energy transfer of 81.9 MeV·cm²/mg.

The rad-hard buck controller incorporates load line regulation and fixed-frequency peak current mode control, which is reported to deliver exceptional transient response while reducing the number of output capacitors required. In addition, the high step-down voltage ratios, combined with the 5-V half-bridge gate driver, simplify the design process and minimize component count for a more compact and efficient power management design.

The high level of integration also improves system reliability and reduces the risk of component failure, Infineon said.

The RIC70847 buck controller is housed in a hermetically-sealed 24-lead flatpack or die form, and works seamlessly with logic-level transistors, such as Infineon’s rad-hard R8 power FET. It is available now, along with the RIC70847EVAL1 DC/DC buck controller evaluation board. The eval board features an integrated dynamic load step circuit for transient testing and supports a range of output capacitance and inductor configurations.

The post Rad-hard buck controller integrates gate drive appeared first on EDN.

Vishay Intertechnology, Inc. launches a new series of insulated, surface-mount inrush current limiting positive temperature coefficient (PTC) thermistors. The Vishay BCcomponents PTCES series devices offer maximum energy handling up to 340 J with high maximum voltages of 1,200 VDC in a compact package, providing increased board-level efficiency and lower costs in automotive and industrial applications.

Vishay said the new PTCES PTC thermistors offer up to 260% higher energy-handling capabilities compared to competing devices, which helps to reduce component count to save board space and lower overall costs. These devices also offer 20% higher maximum voltages than competing devices.

(Source: Vishay Intertechnology, Inc.)

The PTC thermistors provide current limitation and overload protection in AC/DC and DC/DC converters; DC-Link, energy dump, and emergency discharge circuits; on-board chargers and battery charging equipment; and motor drives. They withstand >100,000 inrush power cycles and are AEC-Q200 qualified for shock and vibration, eliminating the need for reinforced mounting adhesives, Vishay said.

The series is comprised of solder-connected homogeneous ceramic PTCs encapsulated in a UL 94 V-0 compliant, self-extinguishing, washable plastic housing with insulation up to 3 kVAC. The devices feature a low profile of 9.6 mm and can be automatically mounted by pick-and-place equipment to reduce placement costs.

The PTC thermistors are RoHS-compliant and halogen-free. Samples and production quantities are available now, with lead times of 10 weeks. Pricing for U.S. delivery starts at $0.90 each in quantities of 1,000. Click here for the datasheet.

The post PTC thermistors save space appeared first on EDN.

While compute devices such as CPUs, GPUs, and XPUs are stealing the limelight in the artificial intelligence (AI) era, there is an increasing realization that powering AI at scale demands new power systems and architectures. In other words, data center operators are investing heavily in high-performance computing for AI, but there is no AI without power.

The exponential growth of AI is rapidly outstripping the capacity of the current 54-V data center power infrastructure, driving a transformation toward high-density, reliable, and safe 800-V powered data centers. Here, at this technology crossroads, the new power delivery architecture requires new power conversion solutions and safety mechanisms to prevent potential hazards and costly server downtimes.

Figure 1 AI data center power was a prominent theme at Infineon OctoberTech Silicon Valley 2025. Source: Infineon

At Infineon’s OctoberTech Silicon Valley event held on 16 October 2025 in Mountain View, California, this tectonic shift in data center power infrastructure was a major highlight. The company demonstrated 800-V AI data center power architectures built around silicon, silicon carbide (SiC), and gallium nitride (GaN) technologies.

Infineon has also joined hands with Nvidia to maximize the value of every watt in AI server racks through modular and scalar power architectures. The two companies will work together on data center power aspects, such as hot-swap controller functionality, which enables future server boards to operate in 800-V power architectures. It will facilitate the exchange of server boards on an 800 VDC bus while the entire rack continues operating through controlled pre-charging and discharging of the boards.

At Infineon OctoberTech Silicon Valley, Peter Wawer, division president of green industrial power at Infineon Technologies, spoke with EDN to explain the transition to AI data centers to 800-VDC architectures. He also walked through the demo to show how 800-V power is delivered to AI server racks.

The advent of solid-state circuit breakers

“We are seeing a switch to an 800-VDC architecture in AI data centers, which is a major step forward to establishing powerful AI gigafactories of the future,” Wawer said. “The power consumption of an AI server rack is estimated to increase from around 120 kilowatts to 500 kilowatts, and to 1 megawatt by the end of the decade.”

Inevitably, it calls for higher efficiency and reduced losses as computing power continues to scale at an unprecedented rate. “This evolution brings new challenges,” Wawer acknowledged. “When you want to exchange server boards on an 800-V bus while the entire rack continues operating, you are dealing with substantial power levels.”

For instance, engineers need controlled pre-charging and discharging to avoid dangerous inrush currents and ensure safe maintenance without downtime. While traditional protective devices like fuses and mechanical breakers have served reliably for decades, they were not designed for the ultra-fast fault response required in today’s high-voltage, high-speed environments, where microseconds matter.

That’s where the next generation of solid-state circuit breakers (SSCBs) comes in. The new data center architectural shift is leading to the emergence of SSCBs, which will modernize AI data centers while replacing electromagnetic transformers. SSCBs respond to faults in microseconds with very high precision, which makes power distribution in AI data centers safer, faster, and more efficient.

Figure 2 SSCBs will replace electromagnetic transformers that currently connect the grid to power infrastructure in data centers. Source: Infineon

“To enable these next-generation SSCBs, Infineon introduced the CoolSiC JFET family earlier this year,” Wawer told EDN. “These JFETs offer the ability to combine ultra-low on-resistance—1.5 mΩ at 750 V and 2.3 mΩ at 1200 V—to ensure robust performance even under tough conditions.”

Reliability is another key advantage, he added. “These JFETs are designed to handle sudden voltage spikes and current surges, responding quickly to faults and helping prevent equipment damage or downtime.” Their packaging—aided by top-side cooling and Infineon’s .XT interconnect technology—helps AI data center power systems stay cool and reliable even in the most demanding environments.

These JFETs also reduce the need for external clamping circuits, simplifying system design and enabling more compact and cost-effective solutions. Besides AI data centers, this SSCB technology can help protect electric vehicles (EVs), industrial automation and smart grids, making power distribution safer, more efficient, and ready for the future.

Solid-state transformers, hot-swap controllers, and power modules

At OctoberTech Silicon Valley, Infineon also demonstrated a power system built around high-voltage CoolSiC components for high-voltage DC power distribution to IT racks powered by a solid-state transformer (SST). “The SSTs will be crucial in gigawatt-scale AI datacenters,” Wawer said.

An SST is a power-electronics stack for connecting the grid to data center power distribution. It replaces the conventional systems based on a low-frequency transformer made of copper and steel and an AC-DC converter, enabling a dramatic reduction in size and weight, end-to-end efficiency, and reduced CO2 footprint.

Next, Infineon unveiled a reference board for hot-swap controllers for 400-V and 800-V power architectures in AI data centers. The hot-swap controller functionality is vital to providing the highest levels of protection, maximizing server uptime, and ensuring optimal performance. The REF_XDP701_4800 hot-swap controller reference design is optimized for future 400-V/800-V rack architectures.

Figure 3 Hot-swapping controller designs demonstrated at OctoberTech in Silicon Valley are optimized for 400-V/800-V data center rack architectures. Source: Infineon

Then there were trans-inductance voltage regulator (TLVR) modules specifically designed for high-performance AI data centers. Infineon’s TDM22545T modules combine OptiMOS technology power stages with TLVR inductors to bolster power density, improve electrical and thermal efficiency, and enhance signal quality with reduced transients.

The proprietary inductor design delivers ultra-fast transient response to dynamic load changes from AI workloads without compromising electrical or thermal efficiency. Moreover, the inductance architecture minimizes the number of output capacitors, reducing the overall size of the voltage regulator (VR) and lowering bill-of-materials (BOM) costs.

Figure 4 The TLVR modules deliver benchmark power density and transient response crucial in AI data centers. Source: Infineon

Transition to new power architectures

Jim McGregor, principal analyst at Tirias Research, acknowledges that it’s becoming increasingly challenging to power AI data centers from the grid to the chip level. “It’s critical that power design engineers continuously improve efficiency, power density, and signal integrity of power conversion from the grid to the core.”

Especially when an AI server costs 30 times as much as a traditional server. Furthermore, there is an increasing need to simplify system design, enabling more compact, cost-effective solutions for powering AI data centers.

The imminent shift from the current 54-V data center power infrastructure to a centralized 800-V architecture is part of this design journey in the rapidly evolving world of AI data centers. That inevitably calls for new building blocks—hot-swap controllers, SSCBs, and SSTs—to successfully migrate to new power architectures.

These power-electronics building blocks are now available, which means the transition to 400-V/800-V AI data centers isn’t far off.

Related Content

• Solving power challenges in AI data centers
• AI Data Centers Need Huge Power-Backup Systems
• EDN Talks to Infineon About the AI Data Center Evolution
• Data center power meets rising energy demands amid AI boom
• As Data Center Growth Soars, Startup Uses AI to Cut Power Binge

The post The transition from 54-V to 800-V power in AI data centers appeared first on EDN.

In one of my recent teardowns, commenting on the variety of piece parts included with the manufacturer’s various products in its streaming media box line, I noted:

I would not want to be the person in charge of managing onn. product contents inventory…

Seeming diversity, but under-the-hood commonality

Multiply that sentiment by 100x or so and you’ve got a sense of my feelings about the poor folks who manage the inventories of (and forecast the future sales of) router manufacturers’ product lines. Today’s teardown victim is from Linksys, but the situation’s very much the same at ASUS, (Amazon) eero, Netgear, TP-Link or any of the other hardware providers.

There are now only a few foundation silicon suppliers, and (unlike the relatively recent past), the pace of technology evolution has notably slowed of late, particularly in the wireless realm. The most significant innovation of the past decade has been mesh networking, which only indirectly deals with the Wi-Fi signals being broadcast to and from any particular network node, mostly focusing instead on the node-to-node handoffs as LAN clients move through the network.

The results? Supplier-to-supplier and product-to-product enclosure and other cosmetics differences, but based on essentially the same underlying hardware, differentiated by software (along with, for example, antenna type and quantity and DRAM capacity variations), as each company strives to differentiate in any (preferably low-cost) way possible to squeeze whatever profit is left from an increasingly mature market. Sometimes, product line diversification (as we’ll see today) involves little more than new stickers on the outside of the device and packaging and an altered product name embedded in the firmware. And all this tweaking ends up causing ongoing stress headaches for each company’s pitiable product line managers.

Prepping for a sooner-or-later home office LAN transition

Today’s analysis is a prescient example of what I’m conceptually talking about…two examples, although, at least for the foreseeable future, you’ll only be seeing the insides of one of them. At the tail end of one of my writeups from late last year, wherein I unsuccessfully (to date, at least) strove to figure out how to eliminate my LAN’s ongoing dependence on the lightning-sensitive spans of wired Ethernet running around the outside of my house, I mentioned that:

I also plan to eventually try out newer Wi-Fi technology, to further test the hypothesis that “wires beat wireless every time”. Nearing 3,000 words, I’ll save more details on that for another post to come.

That “newer Wi-Fi technology” isn’t the primary focus of this post, either, but for now I’ll at least provide an entrée. Right now, I’m running a multi-node LAN mesh based on Google Nest Wifi routers, which implement Wi-Fi 5 (802.11ac) technology, specifically AC2200 4×4:4 albeit absent MU-MIMO. One other important “twist” here is that the backhaul connection between the network nodes is wired Ethernet, not Wi-Fi. The setup’s been operational for three years now, thankfully running quite stably, actually.

But, as with its OnHub predecessors (one of which, from TP-Link, I tore down back in mid-2020) I’d run in a mesh configuration for the prior five years, Google will eventually end support for Google Nest Wifi in favor of the newer Nest Wifi Pro and its potential successors. Indicative of my forecast, Google already pulled both the Nest Wifi and prior-gen Google Wifi (one of which I dissected back in early 2022) from its online store effective the beginning of 2024 (I plan to dissect both a Nest Wifi router and access point post-support cessation).

At that point, I’ll need to upgrade my LAN once again. Fortunately, I’ve already got the successors in hand…a bunch of them, actually, counting spares. Last September (as well as several times prior, which I hadn’t noticed at the time), Amazon subsidiary Woot sold factory-refurbished Linksys LN1301 routers for $14.99 each (plus $5 off one via a coupon code):

Also known as the MX4300, it’s a beefy Wi-Fi 6 AX4200 unit with one WAN and three LAN wired Ethernet ports, along with a USB 3.0 port, based on a 1.4 GHz quad-core CPU (identity to be revealed shortly) and with 2 GBytes of RAM and 1 GByte of flash memory. It supports both MU-MIMO and OFDMA and claims to deliver up to 4.2 Gbps of aggregate wireless bandwidth.

Linksys also refers to it as a “Tri-band” router, although given that it’s not a Wi-Fi 6E device, this doesn’t mean that it supports the newest 6 GHz Wi-Fi band. Instead, it concurrently supports two different 5 GHz band ranges, one predominantly intended for optional node-to-node wireless mesh backhaul interconnect (with wired Ethernet being the other backhaul option).

Speaking of mesh, here’s the kicker…well, one of the two. Although not advertised as being mesh-compatible, it turns out that if, after you set up the primary router, you then direct-connect other secondary “child” units to it, an undocumented setup menu screen enables activating mesh connectivity between them. And (here’s the other kicker), the LN1301/MX4300 is also supported by both the DD-WRT and OpenWRT open-source communities, providing ongoing-maintained options to Linksys’ closed-source and (likely) end-of-life’d firmware.

To that “end-of-life” note, the fundamental reason why Linksys was selling the LN1301/MX4300 so inexpensively, it turns out, was as an inventory purge; the company then dropped the device (originally intended for use by small businesses, not consumers) from its product line. Upfront suspecting that this was the case, I went ahead and purchased the maximum quantity of ten units per Woot account, and then also asked my wife to pick up another one (using the same $5-off quantity-one coupon) from her Woot account. That’ll give me plenty of units for both my current four-node mesh topology and as-needed spares…and eventually I may decide to throw caution to the wind and redirect one of the spares to a (presumed destructive) teardown, too.

Disassembling a more modest sibling

For now, I’ll focus my teardown attention on an alternative, more humbly equipped Linksys router I subsequently acquired. A month after my LN1301/MX4300 binge, Woot sold a two-pack of factory-refurbished Velop (Linksys’ brand name for its mesh-compatible devices) VLP01 AC1200 routers for $19.99, minus another $5-off coupon, therefore $14.99 plus tax. VLP0102, by the way, is Linksys’ naming scheme for the two-pack…VLP0101 is the single-unit kit, while VLP0103 refers to the three-device mesh bundled variant. Stock images to start:

Walmart’s website indicates that the VLP01 was (it’s now out of stock and presumably EOL’d as well) a Walmart-exclusive product, which explains why you can’t find a dedicated product page for it on Linksys’ own website. Instead, there’s the WHW01 series, spec’d as AC1300 devices. Anyhoo, what prompted my acquisition was three main motivations:

• They were inexpensive, and I already had plenty of LN1301/MX4300s, so I could rationalize devoting one of them to a teardown
• Since I planned on doing wired backhaul anyway, I didn’t need super-robust wireless capabilities, particularly at the mesh node in my wife’s office, and
• This (grammatically-tweaked-by-me) thread at the Woot Forum page caught my eye:
  • Can these be meshed with the previous $15 Linksys router deal (Linksys LN1301 WiFi 6 Router)?
  • Couldn’t find a direct answer on the Linksys site, but someone asked this same question on Reddit, and Linksys answered: “All of our intelligent mesh systems are compatible with each other. Just ensure that you designate the one with superior specifications as the parent or main node.”
  • Yes, you can. I did this. You will need [to set up] the LN1301 as the parent and then set these up as the [child] nodes.

This support page on the Linksys website documents and supports the Woot forum claim.

Packaging and contents preliminaries

Now for some images of our patient, beginning with an outer box shot of what I got…which, I’ve just noticed, claims that it’s an AC2400 configuration (I’m guessing this is because Linksys is mesh-adding the two devices’ theoretical peak bandwidths together? Lame, Linksys, lame…):

Speaking of which, here are those two devices:

Along with what’s underneath ‘em:

Wall wart first, as usual, accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:

Now for the router itself:

“Only” one LAN port this time, along with the WAN port and power input connector:

Onward:

Status LED up top, along with an abundance of (passive; no fan in this design) ventilation holes:

And at the bottom, power and reset switches along with verbiage including the all-important FCC ID, Q87-03331, which interestingly (and unsurprisingly) documents this product as being the WHW01, not the Walmart-relabeled and (slightly) de-spec’d VLP01:

Diving inside

Ordinarily, I would have begun my search for a pathway to the interior by focusing on that bottom panel, but an iFixit teardown of the WHW01 that I’d stumbled across during my research (which, truth be told, I actually didn’t realize until my teardown was complete and I’d begun this writeup was of the same hardware, due to the product name variance and “AC2400” silliness) instead advised me to start at the top instead:

Top off and to the side, complete with flips and focus shifts:

Now standalone:

Next, let’s ditch those two screws:

And now we can (re)turn our attention to the bottom. As usual, the rubber feet are first to go, revealing screw heads underneath ‘em:

Buh-bye:

And we have liftoff:

Another set of flips and focus shifts:

Followed by more standalone shots:

And now, free of its upper and lower encumbrances, the inner assembly lifts right out:

Gotta love those focus shifts! The enclosure’s just so tall, don’cha know:

Clever cooling and wireless connectivity

The inner assembly exhibits some pretty nifty engineering. There’s a metal plate on top of one side of the PCB, a finned heat sink on the other side surrounded by a plastic shroud (to which the Bluetooth antenna is attached), and a plastic grill (that you sorta already saw already from those previous inside-from-top still-assembled shots) on the top end with the 2.4 and 5 GHz antennae stuck to it and the LED mini-PCB inserted within it. Side shots first:

Top end:

And bottom end:

Let’s ditch the plastic piece around the Ethernet ports and power connector first. It unclipped and pulled right off with absolutely no fuss:

Removing three screws enables the extrication of the metal plate on one side of the PCB:

Don’t worry; I’ll be getting to those two Faraday cages shortly:

But first, I want to get the topside plastic grill and the other-side plastic shroud off:

The two Wi-Fi antennas’ connections are begging for unclipping:

There’s the LED mini-PCB, still in place:

And there we are:

Some standalone shots of the top-end grill piece, topside first:

Then the underside:

Now the four…err…side sides:

I’m guessing that “P2” references the 2.4 GHz antenna structure, while “P5” is for…err, again…5 GHz. Agree or disagree, readers?

Next up, the side shroud. Outer portion first, revealing (among other things) the aforementioned Bluetooth antenna:

And now the inside:

Next, the LCD mini-PCB.

The largest chip on this side is labeled as follows:

9633
11 02
D819

My guess is that it’s an LED driver, like this PCA9633 from NXP Semiconductors. And on the other side is, of course, the multicolor LED itself:

From the online documentation for the WHW01 (which, I’m guessing, works the same as the VLP01):

• Blue (blinking): Node is starting up
• Blue (solid): Node is working properly
• Purple (blinking): Node is paired with phone for setup
• Purple (solid): Node is ready for setup
• Red (blinking): Node lost connection to the primary node
• If this is your primary node, ensure it’s securely connected to your modem
• Red (solid): Node lost internet connection
• Yellow (solid): Node is too far from another Velop node

And speaking of which, here’s a link to the PDF of the WHW01 user guide, which also references the VLP01 on the cover page!

Next up, let’s get that big finned heatsink off:

Fortunately, with all the retaining screws now removed, it lifted right off straightaway:

Oh, goodie, two more Faraday cages underneath!

Let’s deal with these first, before returning to the two on the other side that we saw before:

Remove the thermal tape from the inside of one, bend back the other…

And surprisingly, at least to me, the system SoC is not on this (formerly finned heatsink-augmented) side of the PCB. On the left is a Winbond W632GU6MB-12 2 Gbit DDR3 SDRAM. And on the right is a CSR (now Qualcomm) 8811 Bluetooth 4.2 controller, unsurprising given the antenna connector’s proximity to it.

There’s one more chip I want to point out on this side of the PCB, at the bottom:

It’s a Macronix MX25L1606E 16 Mbit serial NOR flash memory. (Briefly) hold that thought

Multiple nonvolatile memories

Wrapping up, let’s revisit the PCB’s other side, this time post-removal of the black plastic pieces:

At the top is another Winbond device, this time a serial NAND flash memory chip, the 2 Gbit 25M02GV. It’s based on high-reliability SLC (single-level cell) technology, and given comparative capacity, I’m guessing it contains the bulk of system software, with the Macronix chip on the other side relegated to boot and recovery code (or something like that…mebbe it holds updatable configuration data instead, although EEPROM would seem to be a superior choice?).

Cage tops off…

Along the left:

are (top-to-bottom) two Skyworks SKY85330-11 2.4GHz 256QAM RF front-end modules (FEMs), followed by two chips labeled:

SKY
748
2K01D

WikiDevi (or if you prefer, DeviWiki) says that they’re Skyworks SKY7482I001 5 GHz FEMs, although I can’t find such a chip on Skyworks’ website, so once again… I’m pretty sure they’re right about the 5 GHz FEM part, but I’m questioning the specific part number…then again, I can’t find an online reference to the SKY7482K01D, either. My working theory is that we’re actually looking at the SKY85748-11, and Skyworks just didn’t have room to print the “85” portion of the part number on the package.

To their right, and formerly under two pads of thermal tape, one connecting the cage to the metal plate and the other between the cage and IC, is the dominant heat generator of the design, Qualcomm’s IPQ4018 dual-band 802.11ac controller, which also handles wired Ethernet MAC duties. To its right is the companion Qualcomm Atheros QCA8072 dual-port Ethernet PHY. So basically what we’ve got here is a Linksys-branded and software-customized Qualcomm reference design. And above the QC8072 (and below the two wired Ethernet ports) is the Link-PP HN36201CG dual-port transformer module. There’s nothing notable under the sheet metal square in between the IPQ4018 and QCA8072, by the way, in case you were wondering.

More than 2,500 words in, that’s “all” I’ve got for you today. There’s another surprise waiting in the wings, but I’ll save that for another teardown another (near-future, I promise) day. Until then, please share your thoughts with me (and your fellow readers) in the comments!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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• Inside Walmart’s onn. 4K Plus: A streaming device with a hidden bonus

The post A fresh gander at a mesh router appeared first on EDN.

STMicroelectronics introduces a new family of 5-megapixel (MP) CMOS image sensors: the VD1943, VB1943, VD5943, and VB5943. These advanced BrightSense sensors accelerate the development of vision applications across a variety of industries, including industrial automation for machine and robotic vision, advanced security including biometric identification and traffic management, and smart retail applications such as inventory management and automated checkout.

(Source: STMicroelectronics)

Suited for high-speed automated manufacturing processes and object tracking, the new sensors provide hybrid global and rolling shutter modes, enabling developers to optimize image capture for their specific applications. This delivers motion-artifact-free video capture (global shutter), and low noise, high detail-imaging (rolling shutter).

Featuring a compact 2.25-µm pixel and advanced 3D stacking, the sensors deliver high image quality in a small footprint. The sensors feature a die size of 5.76 × 4.46 mm and a package size of 10.3 × 8.9 mm with an industry-leading 73% pixel array to die surface ratio. This enables integration into space-constrained embedded vision systems without compromising performance, ST said.

Delivering high-quality imaging in challenging environments, these sensors leverage backside illumination and capacitive deep trench isolation pixel technologies to enhance sensitivity and sharpness, particularly in low lighting conditions. Single-frame on-chip high dynamic range improves detail visibility in both bright and dark areas.

The RGB-IR variants feature on chip RGB-IR separation, eliminating additional components and simplifying system design. This capability supports multiple output patterns, including 5-MP RGB-NIR 4×4, 5-MP RGB Bayer, 1.27-MP NIR subsampling, and 5-MP NIR smart upscale, with independent exposure times and instant output pattern switching. This reduces costs while maintaining full 5-MP resolution for both color and infrared imaging, ST said.

The four sensors are currently available for evaluation and sampling, with mass production scheduled for February 2026. Documentation, evaluation kits, and product samples are available.

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XP Power announces a digital version of its HRF15 series of 15-W DC/DC converters with output voltage and current programming through a PMBus via I2C. These new capabilities address the growing need for automation and remote control in high precision equipment, including mass spectrometry, scanning electron microscopy, and transmission electron microscopy for semiconductor inspection and analytical research.

(Source: XP Power)

Compared with the company’s precision analog version launched earlier in 2025, the digital interface of the HRF15 DC/DC converters makes integration simpler, reduces setup time through a graphical user interface, and accelerates product development. Reliability also improves with advanced monitoring and programming.

Other key features include power supply status flags that deliver visibility into system health and performance, enhancing uptime and protecting sensitive instruments; and data logging and real-time diagnostics that converts complex internal data into actionable insights, enabling users to make quick, informed decisions that result in lower operating costs and enhanced application safety. In addition, multi-unit synchronization enables scalable power architectures.

Suitable for noise-sensitive applications, the HRF15 series features extremely low ripple down to 0.001% (10 ppm), critical for high performance. The units exhibit high stability over time at 10 ppm/hr, delivering consistency and repeatability in sensitive processes. Load and line regulation, down to 0.001%, delivers high performance even in load-dependent applications or where input voltage fluctuates. They also have a low temperature coefficient of 25 ppm/°C, minimizing environmental performance influences.

Single-output voltages can be specified at 10 kV, 12 kV, and 15 kV and each unit can deliver 15 W of power from a 24-VDC input. The output rail is fully adjustable for constant current and constant voltage from 0 to 100%, which addresses a wide range of loads.

The HRF15 series carries UL6101O and UL62368 safety approvals. Housed in a case measuring 33.0 × 72.4 × 161.0 mm, and weighing approximately 465 g, the compact units ease integration into space-constrained applications. They are currently available from Avnet Abacus or direct from XP Power with a three-year warranty.

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We might tend to take the word “diode” for granted if we’re thinking of a “diode” as just a two-lead or two-terminal device that gets used in this or that place for this or that purpose. It can become a bit humbling to contemplate just how many kinds of diodes we actually have at our disposal and what they’re used for.

Let’s take a brief, if super-simplistic, look. The schematic symbols shown for each case are not the only applicable symbols I’ve ever seen. In some cases, there are symbol variations in use, but these few shown here will just have to suffice for now.

1. Rectifier Diode (power, signal)

This is a device that simply carries an electrical current in one direction and blocks current flow in the other direction. It can be a small and familiar device like the 1N4148 or something pretty big like a 1N4045 275A 100-V rated diode for a bridge rectifier for wind turbine generator service, or bigger still. It can also be a piece of pencil lead touching a rusty razor blade, a stiff wire (a cat’s whisker) making a point contact on a block of galena, or a low-power, point-contact germanium diode like the 1N34A.

2. Schottky Diode (hot carrier)

This kind of diode is made by forming a junction between a metal (many different types of metal can be used) and some semiconductor material. It has the advantage of a lower forward voltage drop than a semiconductor-to-semiconductor diode and very little storage charge, resulting in a really fast turn-off time.

3. Step Recovery Diode

This device is a semiconductor-to-semiconductor diode with a useful amount of stored charge that allows a brief conduction time in the reverse direction. Time things right and you can cause the reverse conduction to halt at the 270° point of an input RF sinusoid when the storage charge very abruptly runs out. Extremely abrupt current halts make this device a really nice harmonic generator in frequency multiplier applications.

4. PIN Diode (P-type semiconductor, intrinsic semiconductor, N-type semiconductor)

This device is a semiconductor-to-semiconductor diode with a useful amount of stored charge that allows intentional conduction time in the reverse direction. For high enough frequencies, typically 1 GHz and up, this diode’s dynamic impedance can be varied by controlling the DC bias current. That variable impedance is useful for making programmable signal attenuators.

5. Photo Diode

A photo diode will generate an electrical output in response to stimulation by light. Some devices can even be used to detect ultraviolet and/or X-rays.

6. Light Emitting Diode (LED)

A light-emitting diode will generate light in response to stimulation by an electrical current. Some diode devices can generate visible light, as red, yellow, amber, green, blue, or white, while others can generate infrared or ultraviolet. My dentist uses a hand-held ultraviolet LED light to speed up the setting process of dental cement. I questioned him about that. He used to expose dental cement to an ultraviolet lamp.

7. Laser Diode

A laser diode uses a PIN diode structure to pump the intrinsic region in the center of that diode into laser action inside an optical cavity. One of these things is hiding inside that laser pointer of yours, and another one is in your CD player.

8. Zener Diode

A Zener diode is an ordinary diode, but one whose reverse voltage characteristic has a deliberately low breakdown threshold. There is very little current flow through the Zener diode in response to the application of a reverse bias voltage until that reverse bias voltage gets high enough to cross the breakdown threshold and induce a substantial current flow. Voltage regulation is a practical application of this effect.

9. Transient Absorbing Diode

A transient-absorbing diode is very much like a Zener diode, but with the ability to withstand brief intervals of high power during breakdown. Protection of electronic circuitry from otherwise damaging voltage transients is the practical purpose of these devices.

10. Back Diode

A back diode is a diode whose reverse breakdown threshold is very low, even lower than the forward voltage drop of other diodes and even lower than the forward voltage drop of the back diode itself. Low-level RF detection is the practical application for these devices.

11. Varactor Diode

A varactor diode is a diode that is normally operated with reverse voltage applied. The capacitance across the reverse-biased device varies inversely with the applied reverse bias voltage. RF tuning, especially the tuning of voltage-controlled oscillators, is the most common practical purpose of these devices.

12. Tunnel Diode (Esaki)

Tunnel diodes are diodes whose voltage versus current characteristic is discontinuous. They have “voltage-controlled negative resistance” properties. As I personally recall, they were invented in 1957 and were once thought to herald a new age in semiconductor technology. Heathkit even made a tunnel diode DIP oscillator, superseding its earlier grid dip oscillator product. Today, tunnel diodes are still available, although not too commonly used.

13. Gunn Diode

Gunn diodes are single-material semiconductors with no PN junction; nevertheless, they exhibit a negative resistance property that can be exploited to make a microwave oscillator. The lack of a PN junction makes some folks object to the word “diode” as a descriptor for these devices, but the term has become a well-known colloquialism, so who am I to try to change things?

14. Current Limiting Diode

This device might not be called a “diode” either, but as with the Gunn diode, there is a commonly used colloquialism. This device is really a junction field effect transistor (JFET) with the gate tied to the source. The voltage versus current characteristic curve is that of a JFET with Vgs of zero, which, when the device is pulled out of JFET saturation by a sufficiently high voltage, behaves as a constant current driver.

15. Vacuum Diode (Yes, we’re looking at tubes too.)

We may have come full circle at this point. This device is thermionic and, just like its solid-state counterparts, it will conduct current only in one direction. Think 5Y3GT and 35Z5GT. If those part numbers don’t look familiar, go ahead and look them up.

16. Mercury Vapor Diode

A close cousin to the vacuum diode, these devices have an internal atmosphere of heated mercury. In fact, you have to allow enough time (60 seconds if I recall correctly) for the filament to make the mercury hot enough to become a vapor before you try to press the diode into actual service. Also, the device must be operated only in the vertical position with the base pins at the bottom and the plate cap on top. When this tube is doing its thing, the ionized mercury glows blue. Think of the 866A, and again, if that part number doesn’t look familiar, go ahead and look it up.

17. Xenon Gas Diode

Another vapor-dependent diode, but this time the atmosphere is xenon. There is no need to heat the xenon before use, as it is already a gas. When this tube is doing its thing, the ionized xenon glows a somewhat yellowish-white color. Think of the 3B28 and again, if that part number doesn’t look familiar, go ahead and look it up.

18. Magnetron

A magnetron is essentially an educated vacuum tube diode used for generating microwave signals. (Please see “Magnetron.”)

19. Cold Cathode Gas Voltage Regulator

This device isn’t normally referred to as a “diode”, but it meets my idea of being one. It is filled with an ionizable gas, which, when it does get ionized, the plate-to-cold-cathode voltage tends to be stable. It’s a lot like a zener diode in that sense, but it has one troublesome trait of which to be aware. The “striking voltage” for which ionization begins is quite a bit higher than the steady state voltage under steady state gas ionization. That yields a negative resistance property, which, if you put capacitance in parallel with this device, yields relaxation oscillation. When this tube is doing its thing, its gas has a violet glow. Think 0A2 (That first character is a numeral zero, not a letter “oh”.) and yet again, if that part number doesn’t look familiar, go ahead and look it up.

I just happen to have one of those on hand:

20. Mogen Diode

An imaginary device dreamed up by the late Bob Pease. No further discussion necessary.

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

Related Content

• Magnetron
• The diode and the drop test
• Sneak diodes and their impact on your designs
• PIN diode drive

The post Diode classifications appeared first on EDN.

As LED systems are increasingly used in automotive applications, Melexis develops a highly configurable, code-free LIN LED driver that simplifies the development of dynamic RGB-LED automotive ambient lighting applications. In addition to reducing development time, the MLX80124 also eliminates the need for embedded software development expertise, Melexis said.

“This is a new level of product for Melexis. With its built-in functionality and full configurability, this IC offers engineers a radically simpler way to create automotive ambient lighting systems—without writing any code,” said Michael Bender, product line director, Melexis, in a statement. “As the world’s first code-free LIN RGB LED driver, the MLX80124 represents a major shift in how automotive lighting electronics are developed. It dramatically shortens design cycles while maintaining all the robustness and functionality expected by OEMs and tier 1s.”

(Source: Melexis)

The MLX80124 smart LIN RGB ambient light controller features an intuitive graphical user interface that engineers use to access configurable parameters without writing or compiling code. It features high-voltage output drivers, each offering configurable current sources up to 60 mA to support RGB ambient lighting configurations. It is fully qualified to AEC-Q100 and compliant with ISO 26262 up to ASIL B for automotive-grade ambient lighting systems, providing full lighting functionality.

The LIN LED driver delivers precise, LED-agnostic RGB color mixing with temperature compensation. Engineers only need to input the correct optical data for their selected LED.

Other features include a suite of diagnostic features, including open/short detection and supply monitoring. The operating temperature range is -40°C to 125°C.

The MLX80124 LIN LED driver, developed using advanced bipolar-CMOS-DMOS technology, is housed in a compact SOIC-8 package and features pin-to-pin compatibility with other Melexis drivers such as the MLX81124 or MLX81123. It is available now.

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Infineon Technologies AG launches two new secured prepaid tags for closed-loop gift cards, reducing the risk of tampering. These new solutions join Infineon’s secured EMV prepaid tag for open-loop gift cards.

(Source: Infineon Technologies AG)

The U.S. Federal Trade Commission reported losses of $212 million for gift or reload cards in 2024. The new secured prepaid tags target closed-loop gift cards, which are processed in retailer-specific or closed-loop environments, and replace the need for visible codes, barcodes, or magnetic stripes with a secured chip using cryptographic mechanisms.

The chips can be accessed using near-field communication (NFC) devices by using a consumer’s phone authenticated with the necessary data, allowing both retailers and consumers to tap the gift card for activation, check the balance, and redeem assets, Infineon said.

Infineon’s secured EMV prepaid tag solution helps mitigate fraud issues for open-loop gift cards by enabling tap-and-pay at any point-of-sale merchant device or retail outlet processed via payment networks.

Infineon’s first partner in the gift card industry is Karta Gift Card Ltd. The company provides support of AES encryption protocols and processing capabilities, offering cryptographic validation to avoid gift card cloning, skimming, and replay attacks, Infineon said.

Infineon’s prepaid tag solutions for gift cards are available today. The new solutions are fully compatible with existing manufacturing infrastructures for smart cards and paper tickets, and the secured EMV prepaid tag solution is fully EMV compatible, supporting the latest approved Visa and MasterCard applets.

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Renesas RA8M2 and RA8D2 MCUs integrate dual CPU cores—a 1-GHz Arm Cortex-M85 and an optional 250-MHz Cortex-M33—delivering over 7300 CoreMark points. RA8M2 devices suit general-purpose use, while RA8D2 MCUs target high-end graphics and HMI applications.

Both groups employ Arm’s Helium vector extension to accelerate DSP and machine-learning workloads. They provide up to 1 MB of MRAM and 2 MB of SRAM, including 256 KB TCM for the Cortex-M85 and 128 KB TCM for the Cortex-M33. The lower-power Cortex-M33 can act as a housekeeping MCU, handling system tasks while the high-performance Cortex-M85 remains in sleep mode, waking only as needed for compute-intensive operations.

With advanced graphics and imaging capabilities, the RA8D2 drives high-resolution TFT-LCDs for rich HMI designs. Its graphics controller supports up to 1280×800 displays via RGB or 2-lane MIPI DSI interfaces, aided by a 2D drawing engine that offloads rendering from the CPU. Camera and audio interfaces include 16-bit CEU and MIPI CSI-2 for vision AI, plus I²S and PDM inputs for voice-enabled applications.

The RA8M2 and RA8D2 MCUs are available now, supported by the Renesas Flexible Software Package for application development.

RA8M2 product page

RA8D2 product page

Renesas Electronics 

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With 10-MHz bandwidth and 50-ns response time, Allegro’s ACS37100 XtremeSense tunneling magnetoresistance (TMR) current sensor enables precise current measurement. It is designed for power-conversion systems using fast-switching GaN and SiC FETs, including EV chargers, solar string inverters, and server power supplies.

At sub-MHz frequencies, conventional magnetic sensors often lack the speed and accuracy needed for stable control and protection loops. The ACS37100 overcomes these limits with its high bandwidth and fast response, providing the high-fidelity current feedback essential for high-speed switching control.

Using XtremeSense TMR technology, the ACS37100 maintains a low noise level of 26 mA RMS across the full DC to 10‑MHz bandwidth, with ±2% sensitivity error over temperature. A voltage reference output supports differential routing in noisy environments, while a fault output provides an adjustable threshold for fast open-drain overcurrent detection.

The device provides reinforced isolation capable of withstanding 5 kV for 60 s (UL 62368‑1) and a basic working voltage of 1097 V. AEC‑Q100 Grade 0 qualification ensures operation over a -40 °C to +150 °C range. Its SOICW‑16 package offers 1.2 mΩ conductor resistance and 8 mm creepage and clearance.

Samples and evaluation boards are available to aid development.

ACS37100 product page

Allegro MicroSystems 

The post TMR current sensor suits high-speed power stages appeared first on EDN.

Manufactured on a GaAs process, the QPA9510 RF power amplifier from Qorvo covers a frequency range of 100 MHz to 1 GHz. It delivers +35 dBm P1dB output and up to 34 dB gain, with on-chip analog gain control over a 70 dB range.

The QPA9510 serves as the final RF amplifier in GSM handsets for the 900‑MHz band and is also suited for FM and UHF applications. It can be tuned across any sub-band within its operating range and achieves 55% efficiency, extending battery life in portable radios and IoT devices. The amplifier operates from a single +2.8 V to +3.6 V supply.

When paired with Qorvo’s low-noise amplifiers, digital step attenuators, and RF switches, the QPA9510 enables complete RF front-end designs for efficient transmit and receive chains in linear communication systems. Housed in a compact 3×3 mm QFN package, it also features a pin-compatible design for reuse across product families.

The QPA9510 and evaluation board are now available through Qorvo’s authorized distributors and on Qorvo.com.

QPA9510 product page

Qorvo

The post RF amplifier powers GSM, FM, and UHF devices appeared first on EDN.

The Microchip PIC32-BZ6 family of wireless MCUs enables multiprotocol product development with advanced connectivity and scalability. These highly integrated devices support Bluetooth Low Energy, Thread, Matter, and proprietary protocols for smart home, automotive, industrial automation, and wireless motor control applications.

Replacing multichip solutions, the single-chip PIC32-BZ6 platform combines wired and wireless connectivity with a range of peripherals and ample memory. Analog peripherals support motor control, while touch and graphics capabilities enable rich user interfaces.

Qualified to Bluetooth Core Specification 6.0, the MCUs also support 802.15.4-based protocols and proprietary mesh networking. Interfaces for wired connectivity include two CAN-FD ports, a 10/100-Mbps Ethernet MAC, and a USB 2.0 full-speed transceiver.

PIC32-BZ6 MCUs are powered by a 128‑MHz Arm Cortex-M4Fcore and offer 2 MB of flash and 512 KB of RAM. A capacitive voltage divider supports up to 18 touch channels, while 12‑bit ADCs, 7‑bit DAC, comparators, PWMs, and QEI simplify motor control.

The PIC32-BZ6 platform currently includes a SoC and an RF-certified module, priced at $3.73 and $5.84 each, respectively, in quantities of 10,000 units.

PIC32-BZ6 product page 

Microchip Technology 

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Fitted with MEMS switches, two fault insertion units (FIUs) from Pickering simulate common faults in MultiGBASE-T1 communication links. The single-slot 40-205 (PXI) and 42-205 (PXIe) modules target automotive hardware-in-the-loop simulation, enabling design verification of networking components such as ADAS controllers at data rates up to 10 Gbps.

Both PXI and PXIe modules provide 4 or 8 channels of impedance-matched, two-wire signal paths that support communication protocols from legacy 10BASE-T1 to the 10GBASE-T1 automotive Ethernet standard. The FIUs help verify safe and consistent controller operation under a range of connectivity faults, including open and short circuits.

Leveraging MEMS technology, the signal channels deliver low insertion loss and VSWR, along with stable RF performance beyond 6 GHz. Fast 50-µs switching boosts test throughput, while the 3-billion-cycle lifetime ensures durability. Each channel handles up to 0.5 A and 100 V between wire pairs, and the 1.6-A fault buses allow multiple channels to share the same fault condition.

The 8-channel 40-205 (PXI) and 42-205 (PXIe) FIU modules are priced at $10,995 each.

40/42-205 product page 

Pickering Interfaces 

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Recently, we’ve seen Design Ideas for programmable current sources with improved accuracy using the LM3x7 series of three-legged regulators. These designs also take advantage of those classic devices’ built-in anti-overheating features. 

Some are very good, like “Improve the accuracy of programmable LM317 and LM337-based power sources.”

Others perhaps not so much…“Cross-connect complementary current sources to reduce self-heating error”…

All of them, however, had to accommodate the LM3x7 family’s need for about 5-V of supply voltage headroom when used this way. That is the voltage drawn from the supply that can never be delivered to the load. It therefore creates significant inefficiency in power utilization. It might have been picky of me, but I couldn’t resist wondering what could be done to improve (reduce) the loss.

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

Current source without overtemperature protection

Figure 1 shows what I started with: A simple, straightforward, accurate, 0 to 1 A current source programmed with 0 to 2.5 V. It needs only about 1.25 V of headroom, consisting mostly of the drop of current sense resistor R1 (plus a modicum more from the Ron of Q1), thus fixing the problem I started out to solve.

Figure 1 An improved efficiency precision current source has no overtemperature protection. With no protection, if the Q1 heatsink is inadequate, high power or ambient temperature might destroy it.

But sadly, in fixing one problem, I created another. 

The same elimination of LM3x7s that reduced the headroom requirement also eliminated overtemperature protection. Without a substantial external heatsink, the Si7489DP FET is rated for only ~6 W at 25 °C. If power dissipation, ambient temperature, or both happen to go higher, there’s now nothing to prevent Q1 from being cooked.

Current source with overtemperature protection

So now I wondered what might be done about that. Figure 2 shows what said wondering (wandering?) inspired.

Figure 2 External junction temperature protection for the Q1 pass transistor. Since Q1’s internal junction temperature can’t be directly measured, it must be inferred from power dissipation, junction to ambient thermal resistance, and ambient temperature. If it tops 150 oC, A1d stops the show. 

What was needed was an external version of the now missing LM3x7’s internal junction overtemperature cutoff. Of course, the challenge with implementing an external junction temperature limiter is that internal transistor junctions are a second cousin to the classic Schrodinger’s cat.

Well, maybe not exactly. Unlike the famous quantum kitty, whose temperature (whether body or room) is theoretically unknowable. Junction temperature, while difficult to directly observe, might at least be calculated. 

And in fact, this is what the right-hand half of Figure 2 does. 

The necessary junction temp math is:

Tj = (Ij Vj)/Sja + Ta 

Where:

Tj	Junction temperature
Ij	Amperage through the junction
Vj	Voltage across the junction
Sja	Thermal conductivity (watts/degree) from junction to ambient from Q1 datasheet
Ta	Ambient temperature

The analog arithmetic

Figure 2’s circuitry performs analog arithmetic by relying on the nifty 17th-century invention of John Napier for multiplication and division: adding and subtracting logarithms. Here’s how the Figure 2 circuitry divides (and multiplies!) up the work.

Q3’s Vbe is the logarithm of the Q1 current programming signal sensed via R6. Meanwhile, Q4’s Vbe logs the voltage across Q1 monitored by Q8 and R6. 

Q3 and Q4 are connected in series, so their log voltages sum. About 400 years ago (now that’s really legacy technology!) Napier showed that adding logs is equivalent to multiplication. So, the sum of Vbe’s becomes the IjVj product term in the Tj math.

The IjVj signal is applied to A1c’s non-inverting input, which then subtracts Q5’s Vbe present on the inverting input. Because subtracting logs equates to division (thanks again, Johnny!), if R8 is properly scaled, this division provides the Sja normalization term for Rja. The quotient yields the log of junction temperature rise above ambient..

The antilog transistor Q6’s collector current, in concert with the R9/R10 network (at long last!) converts A1c’s output to a 2 mV/oC junction temperature signal. That’s summed by A1d with Q7’s ambient temperature signal.

When the sum bumps against Q1’s 150 °C safety limit, A1d’s output ramps positive, overriding the programmed source current to a safe value.

Which you might say is the cat’s meow. 

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

• Cross connect complementary current sources to reduce self-heating error
• Improve the accuracy of programmable LM317 and LM337-based power sources
• Calculator or Slide Rule?
• Special day for physicists’ cats
• Is that a banana in your pocket (or are you just glad to see me)?

The post Programmable current source with overtemperature shutoff appeared first on EDN.

Zoom is a display tool that expands the view of the selected waveform. The source trace can be expanded horizontally and vertically for detailed visual analysis or further processing. Each zoom trace can have its own horizontal and vertical scale setting, enabling views of the source trace using multiple horizontal and vertical scales. All digital oscilloscopes offer zoom functionality.

Zoom is important because oscilloscopes can acquire gigasamples of data per acquisition, with a vertical resolution of 12 or more bits. This data must be displayed on a screen with a resolution of approximately 1920 x 1080 pixels. If a full acquisition is displayed, the data has to be compacted to fit on the screen. Expanding the data with a zoom trace so that it fits within the screen resolution allows a view of all the acquired data.

Zoom demo

Zoom can be invoked from this oscilloscope’s front panel using the Zoom button. It can also be evoked interactively by touching the touchscreen and dragging the resulting box over the area to be expanded. Zoom traces can also be controlled from the Zoom Trace dialog boxes (Figure 1).

Figure 1 An example of several zoom instances used to analyze a remote keyless entry system waveform. The Zoom dialog box is used to control each zoom trace. Source: Art Pini

The source waveform from a remote keyless entry (RKE) system appears as trace M1 in the top grid. The waveform comprises an amplitude-modulated RF carrier. The modulation encodes the commands to lock a car door. Zoom is used to expand the fifth pulse in the acquired waveform horizontally. Note that the zoomed area is highlighted by increased intensity on the source trace. The expanded version appears in trace Z1 (second down from the top). The Z1 trace is controlled using the Z1 zoom dialog box at the bottom of the display.

The trace’s horizontal and vertical scale and offset can be adjusted interactively while observing the effects on the screen. The trace annotation box for the Z1 trace shows the vertical and horizontal scaling for the zoom trace. Trace Z1 has a horizontal scale of 150 microseconds per division, compared to the 5 milliseconds per division scale of the M1 source trace, representing an expansion of thirty-three times.

The zoom trace reveals variations in the RF carrier amplitude at the start and end of the burst. These keying transitions affect the generation of spurious signals that can interfere with other RF services. The zoom trace Z2 expands the view of the trailing edge of the first zoom trace and displays it in detail in the third grid from the top. Here, we have an example of Zoom on Zoom.

The analysis continues by demodulating the signal in Z2 by low-pass filtering the absolute value of the waveform. The demodulated signal can be measured to obtain the signal amplitude’s slew rate and the decaying amplitude’s time constant. This is an example of a math operation on Zoom. The math trace F1 performs demodulation; the result is displayed in the bottom grid. This example used two zooms, each with a different horizontal scale.

Horizontal and vertical scale factors

Zoom, in the oscilloscope used for this article, can be applied to any waveform, acquired signals, math, memory, or even other zoom traces. Zoom traces are waveforms like any other. They can be expanded further using another zoom trace, allowing the same signal to be viewed with multiple horizontal or vertical scale factors.

Math operators can be applied, allowing arithmetic, filtering, or FFTs to be performed on them. The number of available zoom traces generally matches the number of acquisition traces; however, all non-acquisition traces, like math or memory traces, have zoom functionality in this family of oscilloscopes.

Figure 2 provides an example of zoom being used to expand a signal vertically.

Figure 2 The echo in an ultrasonic range finder signal is expanded vertically to see the details of a double signal return. Source: Art Pini

A double echo in an ultrasonic range finder is zoomed vertically to see the detail of the waveform that is not easily discerned on the acquired waveform. The vertical resolution of this waveform is twelve bits or 4096 levels. At least a four-to-one vertical zoom is required to render the full resolution on a display with 1080-pixel vertical resolution. A ten-to-one vertical expansion shows the echo at 5 mV per division, providing a detailed view of the waveform structure.

Multi-Zoom

Some applications use multiple zoom traces with the same expansion factor for comparison purposes. Consider the measurement of an I2C data signal and clock signals shown in Figure 3.

Figure 3 Using time-locked multi-zoom to verify the timing between an I2C data and its associated clock signal. Source: Art Pini

The signal in the top grid is an I2C data signal. The grid immediately below that is the associated I2C clock. These waveforms are expanded synchronously using a feature called multi-zoom. Multi-zoom locks the selected zoom traces together. This feature allows common horizontal control of all zoom traces. They can be expanded or contracted synchronously, locked in time, or offset by a user-defined time offset.

In the example, the zoom traces Z1 and Z2 are the expansions of the data and clock signal, respectively. They are locked in time with no offset. The expanded view makes it easier to see the relative timing of the signals. So, the start condition, where the data signal is forced to a low state, followed by the clock signal being forced low, is easy to discern. The zoom traces incorporate the address field of the I2C packet. The expanded view afforded by the zoom displays is useful in evaluating physical layer issues like signal levels, period, with, transition times, and timing.

The multi-zoom feature also includes an auto-scroll mode to automatically scan through the entire waveform at a user-set rate (Figure 4).

Figure 4 The zoom auto-scroll controls allow automatic scrolling of the zoom horizontal location of the zoom trace to scan through long records. Source: Art Pini

Automatic scrolling is very helpful when moving narrow zoom windows through very long acquisitions that might require an extreme number of turns of a knob. It offers two scan rates and the ability to jump to the extreme values.

Comparing waveform segments

Zoom displays can help compare waveforms. For instance, an acquired I2C data signal contains multiple data packets; Zoom can be used to display these packets on the same expanded timescale for comparison (Figure 5).

Figure 5 Using zoom traces to separate and compare I2C data packets on the same expanded time scale. Source: Art Pini

Packets 1, 2, and 4 from the acquired I2C data bus acquisition are separated and compared using three zoom traces with the same scale factors but with different offsets. It is easy to see the difference in the length of packet 2; the data content of the three packets differs in the last half millisecond of the waveforms.

Using Zoom to window signals

Zoom can select, or window, specific regions of an acquired signal for further processing. This allows the examination of selected parts of a signal separately. Consider analyzing an RKE system that uses frequency shift keying (FSK) to encode commands (Figure 6).

Figure 6 Using zoom traces to isolate the one and zero state frequencies in an RKE system using FSK modulation. Source: Art Pini

The trace in the upper left grid represents 10 ms of a 260-ms-long RKE command. The RKE fob uses FSK to encode the digital one and zero states. The trace below the acquired trace shows that the demodulated FSK data is an NRZ serial signal. The upper-right grid shows the FFT of the acquired RKE signal. The signal has a frequency-modulated 434-MHz carrier. The FFT shows two peaks characteristic of frequency hopping, one corresponding to the frequency of the one state and the other to the frequency corresponding to the zero state.  

Zoom can be used to separate the parts of the acquired signal corresponding to the signal’s 0 and 1 states. Zoom trace Z1 (third grid down on the left) shows the part of the RKE signal matching the zero state shown in the demodulated signal. The duration of the zoom trace is adjusted to fit within the duration of the digital state.

Similarly, the zoom trace Z2 (bottom left) has been used to select the part of the signal in the one-state. The intensified segments on the acquired waveform correspond to the selected regions. FFTs of the zoom traces show that each digital state contributes a specific frequency to the signal.

Measurement parameters identify the zero frequency as 433.888 MHz and the one state as 433.964 MHz. The magnitude of the frequency shift between the two digital states is determined by taking the difference between the two measured frequencies, which is 76 kHz. Zoom has separated the frequencies associated with each digital state.

Note that the FFT’s frequency resolution is proportional to its input’s record length and that the zoom traces are shorter than the acquired waveform and thus will have poorer resolution. This does not matter in this example, where the goal is to determine the frequencies of the two digital states.

Expanding waveforms with zoom

Zoom is a useful tool for studying and analyzing acquired waveforms by providing an expanded view of the signal vertically or horizontally. These traces provide enhanced visual acuity, allowing the instrument’s full amplitude and time resolution to be displayed on the screen. They also select specific parts of a signal, allowing for the analysis of only those portions of the signal that are of interest.

Arthur Pini is a technical support specialist and electrical engineer with over 50 years of experience in electronics test and measurement.

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Kyocera AVX releases the KGP Series of commercial-grade stacked capacitors targeting high-frequency applications in the industrial and downhole oil and gas industries. The new stacked MLCCs deliver higher capacitance values in the same mounting area as traditional capacitors to support miniaturization.

(Source: Kyocera AVX)

These stacked capacitors are manufactured without lead or cadmium to support sustainability and ease standards compliance. They also provide low equivalent series resistance (ESR) and inductance (ESL), minimizing noise and optimizing performance, and feature metal lead frames that reliably suppress thermal and mechanical stress for greater stability and durability. Applications extend throughout the industrial, alternative energy, and downhole oil and gas industries, and include power supplies, DC/DC converters, control circuits, high-voltage coupling, and DC blocking.

The KGP Series stacked MLCCs, in C0G, X7R, and X7T dielectrics, are available in five EIA case sizes (1210, 1812, 1825, 2220, and 2225) with two stack sizes (maximum thicknesses spanning 3.40 to 6.95 mm), and “J” or “L” leads. Key specs include operating voltages ranging from 50 V to 1,500 V, capacitance values ranging from 10 nF to 47 µF ±10% or 20% tolerance, and an operating temperature range from -55°C to 125°C.

The stacked MLCCs with C0G and X7R dielectrics are available in all five EIA case sizes with the full range of rated voltage values and capacitance values up to 220 nF and 47µF, respectively. MLCCs with X7T dielectrics are available in three EIA case sizes (1210, 1812, and 2220) with three rated voltages (250 V, 450 V, and 630 V), and capacitance values up to 4.7 μF.

These ceramic capacitors are tested for a range of factors to ensure performance in challenging high-frequency applications. These include visual characteristics, capacitance values, dissipation factor, temperature coefficient, insulation resistance, dielectric strength, temperature cycling, steady state and load humidity, high temperature load, termination strength, bending, vibration resistance, and soldering heat resistance. They are RoHS compliant and packaged for automated placement on tape and reel in quantities of 500–1,500. 

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Silicon Labs launches its Simplicity Ecosystem, a suite of modular software tools that are designed to simplify embedded IoT development. The Simplicity Ecosystem centers around Simplicity Studio 6 with the upcoming Simplicity AI SDK framework, available in 2026. The ecosystem brings together installation, configuration, debugging, and analysis into a single developer-first environment.

“The Simplicity Ecosystem represents a major step in making intelligent, context-aware development a reality,” said Manish Kothari, senior vice president of software development, Silicon Labs, in a statement. “By integrating AI into every layer of our tools, we will give developers a platform that learns, adapts, and accelerates innovation across the entire IoT lifecycle.”

The new Simplicity Ecosystem extends that legacy of the Simplicity Studio, available for more than a decade, by breaking the toolchain into modular, interoperable components. These components fit seamlessly into modern workflows, whether they are GUI-based or automated, and can work independently or as part of the ecosystem.

The Simplicity AI SDK will allow developers to chat with their code through new AI-powered integrations. (Source: Silicon Labs)

The core tools include the Simplicity installer for on-demand installation of SDKs, examples, and tools; VS code and CLI integration; device manager for a unified interface for identifying, managing, and programming Silicon Labs hardware; Simplicity commander, a command-line for programming, debugging, and security configuration; a network analyzer protocol-aware tracing tool for wireless traffic, with real-time visibility into packet exchanges across Bluetooth LE, Zigbee, Thread, and Matter networks; and the energy profiler real-time measurement tool that correlates energy consumption directly to code execution. It also includes a full suite of configuration, control/debug, and analysis tools for all wireless technologies.

The software tools ecosystem supports Silicon Labs Series 2 and Series 3 devices and major IoT standards, including Bluetooth LE, Zigbee, Thread, Matter, Wi-Fi, Wi-SUN, and Z-Wave.

The Simplicity AI SDK  framework will enable an AI-augmented workflow, supporting engineers  by acting as a collaborator that interprets code, surfaces insights, and assists with tasks across the lifecycle from project setup to field debugging. It combines context awareness and intelligent automation to accelerate development.

The first release will integrate with VS code to let developers “chat with their code,” marking a shift toward AI-assisted design, Silicon Labs said. It can explain functions, trace errors, and suggest improvements in real time, using an understanding of project context and Silicon Labs SDKs.

Dynamic context engineering is at the heart of Simplicity AI SDK, the company added, giving AI agents the right data at the right time to understand project structure, interpret documentation, and provide contextual support without manual lookup.

The Simplicity AI SDK will be available in 2026, beginning with developer feedback and beta testing. You can join the Simplicity AI SDK early access waitlist. Future updates will extend these capabilities across Silicon Labs’ tools, enabling adaptive debugging, optimization, and application generation. Simplicity Studio 6 is available now for download.

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An EDN Design Idea (DI) presented a discussion of how to increase the resolution of an ADC by adding a non-deterministic, zero-mean, Gaussian noise dither waveform to a signal to be converted; then, oversampling the sums, and low-pass filtering (thereby averaging) the ADC conversions. (As noted, a filter that optimally removes out-of-band high-frequency dither noise is generally more complex than a simple averager.)

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

Conversions are executed at a rate of M times that are required to satisfy the Nyquist condition. Low-pass filtering them offers an increase in resolution of a factor of M and of B = log2(M) bits.

The signal at the filter output has negligible energy above the Nyquist frequency, and so only every Mth output of the filter needs to be sampled in a process known as decimation. Even though the resolution of the conversions has been increased by a factor of M, the signal-to-quantization noise ratio has not improved by the same amount. Because there is still non-deterministic noise present below the Nyquist frequency, it turns out that the signal-to-quantization noise ratio has improved only by a factor of sqrt(M) and by sqrt(B) bits.

Avoiding dither-associated noise

But what if the signal were DC and the dither were known, deterministic, and repeated every M samples? The addition of dither-associated noise could be avoided if a judiciously selected dither waveform were added to the signal to be converted and its mean subtracted from the average of M conversions. A simple averager would suffice for the filter. (And if the dither were zero-mean, there would be nothing to subtract!) The advantage of this approach would be that the signal-to-quantization noise ratio would be improved by the same amount as the resolution.

So, what might constitute a “judiciously selected” dither waveform? I won’t keep you in suspense: a sawtooth whose peak-to-peak amplitude is an odd integral multiple of the size of the least significant bit (LSB) of the ADC fits the bill. Why only “odd”? Let’s see why the odds work and why the evens are not as good choices.

Examining the effects of dithering

In examining the effects of dithering, it’s convenient to work with integer values. For example, let’s assign the smallest possible ADC conversion step size value not to 1 as is traditional, but to M, which is also the number of conversions to be averaged to produce an output. Consider the case of M equal to 64.

Accordingly, all ADC conversions are integral multiples of M: 0, 64, 128, etc., whereas the dither ramp takes on the values of d = 0, 1, 2… 63. Each dither value is added to an input value of (for example) 42, and each sum is converted.

There will be 42 conversions of value 64, and 22 conversions of value 0. The average is 42. We have our increase in resolution! This works for input signals of 0, 1, 2… and up to and well beyond 63.

It’s limited only by the input conversion range of the ADC. Notice that some very large input signals, which by themselves are within that conversion range, will, when added to portions of the dither waveform, be moved above that range. In such cases, the averaging process will yield incorrect results. These input values are in the “dither-disadvantaged” range.

For dither to be of value, it must be added to the signal prior to A-to-D conversion; that is, the dither is an analog signal. But analog or digital, a question arises as to its optimal peak-peak range. Should it take on exactly the values discussed above? Or should each of these values be multiplied by some number? An Excel program was written to answer this question by examining sets of signals plus dither of the form of Expression (1):

S + si + dk  · Aa  (1)

Table 1 describes each variable.

S	Any arbitrary multiple of M = 64 such that Expression (1) is entirely within the ADC conversion range
si = i, where i = 0, 1, 2… 63	Where S + si constitute a set of input signals
dk = k – 31.5, where k = 0, 1, 2… 63	Where the -31.5 renders dither dk zero-mean, but requires a compensatory value of 31.5 to be added to the average of sets of M ADC conversions
Aa = a/10, where a = 7, 8, 9… 70	Where Aa is the peak-peak value of the dither in units of 1 LSB

Table 1: The variables in Expression (1) that an Excel program was built around to examine sets of signals plus dither.

Expression (1) is evaluated for the full range of si for every given Aa. ADC conversions yielding multiples of 64 are determined for each value of dk.

These conversions are averaged, added to 31.5, and the sum converted to an integer. The number of errors ei,a (0, 1, 2…) in units of 1/64 of an LSB are determined by subtracting this result from S + si.

The errors are then graphed against si for each peak-peak dither amplitude Aa.

This eye chart appears in Figure 1. Confusing, impressive, or both, it’s difficult to get too much useful information out of it. But it’s clear that even though there are errors in most cases, their magnitudes are small compared to the resolution of a single ADC conversion; useful resolution enhancement has been achieved.

Figure 1 An eye chart with the errors of dithered input signals of amplitudes 0 to 63 for and ADC whose LSB is 64.

Additional calculations

To derive more useful information so that the best values of Aa can be identified, some additional calculations are performed. For each Aa, the ei,a are squared, summed over all i, and the square root of the average of the sum is taken to produce the rms error erms. This provides a figure of merit for each scaled peak-peak range Aa of dither. erms is graphed against Aa in Figure 2.

Figure 2 The RMS errors of all input signals with dither added, providing a figure of merit for each scaled peak-peak range Aa of dither.

What is clear from this graph is that zero errors can be obtained if the peak-to-peak dither amplitude is an odd multiple of the ADC conversion LSB. To understand why this happens, consider multiplying dither elements -31.5, -30.5… 31.5 by an odd integer and taking the modulo M = 64 portion of the products.

Surprisingly, you’ll find every number in the basic dither sequence of 0, 1, 2… 63. This gives full coverage to every possible value of input S + si. But why aren’t even multiples error-free?

The modulo 64 of products with even integer multiplicands are even numbers only; the odd elements of the basic sequence are missing. And when Aa is not an integer, the rms errors are generally (although not always) even larger. It could be challenging to generate an analog signal whose range is an exact odd multiple. To minimize the error due to an inexact dither amplitude, we might skip the choice of Aa equal to 1 and choose a multiplier of 3 or 5.

A dither generator

A suitable circuit for generating and using a non-zero mean dither waveform is shown in Figure 3.

Figure 3 A suitable circuit for generating a non-zero mean dither waveform.

At the start of a string of conversions, d2 is set to 0 V to disable M1 while d1 is connected to a reference voltage Vref, such as the one used by the ADC. This allows C1 to begin to charge.

After the last conversion, d1 is left open or grounded, and d2 is set high to enable the MOSFET and quickly discharge the capacitor. Because the peak value of the dither voltage is such a small portion of Vref, what would normally be a signal involving a negative exponent of time is well-approximated as a linear ramp of:

Vref · t / T, where T = R1 · C1

Assuming that the M conversions are equally spaced in time and last for Tsam seconds, T is selected so that the desired Aa is equal to:

Aa = Vref · Tsam / T

The intended signal is obviously not zero-mean. And there is also a small amount of charge injection into C1 when the MOSFET shuts off due to that device’s parasitic capacitances. (A MOSFET with minimal capacitances and a fairly large C1 will work together to limit the size of the charge injection voltage offset.)

Fortunately, even a simple calibration scheme that converts known small and large signals and fashions a best-fit linear correction out of these renders the offsets inconsequential. Note that the dither waveform is subtracted from rather than added to the input signal. This means that the smallest rather than the largest input signals that alone would be within the ADC conversion range are now the ones in the dither-disadvantaged range. If this is of concern, The R resistor connected to ground in Figure 3 can be replaced with a resistor divider presenting the same resistance as R and driven by Vref. A small division ratio is chosen to ensure that all ADC inputs are positive. This returns the dither-disadvantaged range to the larger of all possible ADC conversions. 

Errors

The increase in resolution should not be confused with improvements in accuracy; no ADC is ideal. All have integral and differential non-linear errors.

Dither-related ADC improvements

A means has been presented of generating a dither waveform and employing a method using it to enhance the resolution and signal-to-quantization noise of ADC conversions by a factor M, where M is the number of conversions per sample of a DC input signal. A simple calibration technique is required involving the use of ADC conversions of known small and large signals to afford gain and offset error compensation. It should be noted that the application of dither to increase ADC resolution is still, to some extent, at the mercy of the ADC’s accuracy.

Blue sky possibilities

If we wish to consider AC input signals rather than only DC ones, it would be possible to digitally subtract the dither value associated with each conversion from that conversion. Perhaps an averager would still suffice as the filter, perhaps not. Perhaps overall performance improvement would not be as good as with a DC signal, or maybe it would. I’ll do some further analysis, but I also invite comments on the matter. 

With AC signals, we don’t have the luxury of waiting for the capacitor in the sawtooth generator to discharge; sampling should be at an uninterrupted, constant rate. Instead of a sawtooth, a triangle wave of the same peak-to-peak amplitude would work.

It could be created with a square wave driving an R1-C1 lowpass filter whose output is capacitively coupled to the unity gain op amp input of Figure 3 in place of the sawtooth generator.

This input would be referenced through a large resistor to ground or to a DAC voltage within the op-amp’s common-mode input range. Dither-disadvantaged ranges might now exist at both extremes of the ADC conversion range. Dealing with such ranges was discussed with sawtooth dither, and the same method can be employed with the triangular waveform. Successive sets of M conversions would occur on rising and on the falling ramps of the triangle wave. The triangular dither waveform would work with DC signals, too, and has the advantage of eliminating MOSFET charge injection.

But with or without a dither waveform, annoying artifacts can arise whenever there is correlation between the periods of the conversion rate and the AC input signal. It is expected that with the dither discussed, artifacts would be M times smaller than without dither.

A known solution to the artifacts problem is to add a small, random analog dither waveform. This will, of course, have a negative impact on signal-to-quantization noise, but the tradeoff may be worth it. I suspect that the magnitude of the new dither should be the size of the ADC’s LSB, but once again, I will investigate, and I do invite comments.

Acknowledgements

I’d like to acknowledge significant contributions to the development and readability of this DI by someone who wishes to remain anonymous.

 Christopher Paul has worked in various engineering positions in the communications industry for over 40 years.

 Related Content

• Increasing bit resolution with oversampling
• Frequency dithering enhances high-performance ADCs
• Dithering increases dynamic range in digital-radio system
• Analyzing ADC Noise Impacts on Wireless System Performance

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