App note: Virtually increasing the number of serial communication peripherals in STM32 applications

App note from STMicroelectronics on possible alternate switching of channels to cater multiple communication routes. Link here (PDF)

Application engineers often face the problem of limited number of serial communication peripherals of a microcontroller that, on the other hand fulfills all the other application requirements thanks to its features and performance. Sometimes they obviate by switching to a higher level microcontroller with sufficient number of communication peripherals. This migration brings with it additional (often unused) performance and functionality, in most cases unneeded and not used by application, in addition to increased costs and PCB complexity.
A frequent case is when full (or specific) functionality is not required for each and every channel, in this case the communication flow and its control can be simplified radically (e.g. communication is required at specific modes or time slots only, communication speed can be lower, correct timing is not strictly required for all the signals, simplified protocol or flow is acceptable). In these specific cases the user would really benefit from methods on how to supplement the missing channel(s) with current HW, to avoid needless migrations.

App note: Power transistor safe operating area – special considerations for switching power supplies

App note from ON Semiconductors about less common transistors stresses when used on switching power supplies. Link here (PDF)

The power transistor, in today’s switching power supply, exists in an environment which is quite hostile to semiconductors. Large currents, large voltages, high temperature, high frequency, and low impedance sources add up to something close to the worst of all possible worlds for the transistor.
Given this type of environment, it is not surprising to find that keeping transistor stresses within acceptable limits can be quite a challenge. Transistors designed and specified specifically for switching power supplies help, but do not in themselves guarantee a reliable design. Very often, reliability is determined by the more subtle aspects of how stress imposed by the power supply relates to transistor safe operating area.

App note: Bring a “CAN-DO” attitude to your industrial drone design

Tech note from Maxim Integrated on using the proven robustness of CAN Bus to drone’s internal parts communication. Link here (PDF)

Providing predictable and error-free communications, CAN bus networks have been the workhorse of the automobile industry for over thirty years. However, they have recently found a new lease on life in other industrial applications, including drones. In this design solution, we show where and how CAN transceivers can be used in drone designs and explain why it is important that they come with the high levels of electrical protection when used in this application.

App note: Automotive infotainment gesture control for the rest of us

Gesture recognition discussed in this tech note from Maxim Integrated. Link here (PDF)

Infotainment gesture control enhances driver experience and safety by helping avoid distractions caused by fiddling with touchscreens and poorly located dials. Gesture recognition can complement touchscreens, voice, and knobs so that the driver can focus on the road. Time-of flight cameras, although fancy, are computationally heavy and expensive. A new, disruptive approach integrates the use of optics, sensing, and an analog front-end in a single ASIC, dramatically reducing cost and advancing the adoption of this important technology in a wider tier of automobiles.

App note: High current LED capacitive drop drive

Fairly old app note from ON Semiconductors on using capacitors to drive LEDs off AC mains. Link here (PDF)

This application note describes the basics for powering high current light emitting diodes (LEDs) utilizing a capacitive divider circuit off the AC mains. A linear regulator is used to control the LED current in order to ensure optimal performance and long life. LED characteristics are explained, followed by an example design to illustrate the concept.

App note: A guide to choosing the right ultra low Iq low dropout linear voltage regulators

App note from ON Semiconductors that discuss tradeoffs between achivieng low quiescent current and good dynamic performance when choosing an LDO. Link here (PDF)

One of the most important challenges today in designing electronic applications is to minimize the power consumption of the system. To accomplish this, most systems utilize various low power modes which help to minimize the overall power consumption. When utilizing various modes of operation, system supply currents can easily vary from single A or even fractions of A in sleep to tenths or hundreds of mA in full power mode. Low Dropout Linear Voltage Regulators (popularly referred to as LDOs) are common building blocks in any power system and the choice of linear regulator can have an important impact on the overall system power consumption. To complicate this choice, it is often required that the LDO not only feature ultra−low quiescent current but should additionally provide good dynamic performance to assure stable, noise−free voltage rail, suitable for sensitive circuits.

App note: Snubber design for noise reduction in switching circuits

Minimize noise by properly designing a snubber circuit in switching converters, app note from Alpha & Omega Semiconductor. Link here (PDF)

In high frequency switching converters the designers face a common challenge of dealing with switching noise. In particular when the high side Mosfet turns on, the body diode of the low side FET, which was in conduction before, turns off. During the turn off process the body diode draws a peak reverse recovery current and then abruptly snaps off. Since there is a small but finite parasitic inductance in the circuit, the reverse recovery current will circulate through the circuit until it dies down. This will result in voltage overshoot and ringing at the phase node which is quite undesirable. If the overshoot is severe enough, the low side FET may turn on again or go into avalanche breakdown. On the other hand the ringing may cause negative spikes with respect to ground, and these spikes may get coupled to the sensitive electronic components in the load causing malfunctions.

App note: Power MOSFET continuous drain current rating and bonding wire limitation

App note from Alpha & Omega Semiconductor about current limitations on MOSFETs with exposed pads. Link here (PDF)

Power MOSFET datasheets will usually show maximum values for continuous drain current Id, on the first page of datasheets.
For bottom exposed part such as DPAK, TO220, D2PAK, there is always a note besides Id rating saying that Id is limited by bonding wires. Is this true? The answer is no for most of the cases.
The reason would be shown in this article and more studies will be present to show, how low the silicon resistance should be to lead to a bonding wire limitation issue.

App note: Wireless gamepad solution based on LPC5528 and NxH3670

Application note from NXP Semiconductors introduces a wireless gamepad solution based on LPC5528 and NxH3670. Link here (PDF)

LPC5528 is a Cortex®-M33 based microcontroller for embedded applications. It has two USB device controllers which are key peripherals for the gamepad solution: Full-speed USB and High-speed USB device controllers. All of these features make LPC5528 very suitable as a gamepad or headset host controller. NxH3670 is a ultra-low-power 2.4 G wireless transceiver. It integrates a Cortex-M0 processor and has passed the Bluetooth Low Energy 4.2 certification. It has low latency and low power consumption characteristics and is used in wireless gaming headset products.

The main functions implemented are as follows:
• Wireless mode
USB cables are not required to connect PC (game console) and gamepad.
• Wired mode
When the battery of gamepad is exhausted or there is no USB dongle module, the gamepad can be connected to the PC (game console) through a USB cable to make the gamepad work in wired mode and charge the battery.
• Audio playback and recording function
When the gamepad is working in wireless mode, the audio data on the PC is transmitted to dongle board through the USB interface, and then the audio is transmitted to the gamepad through the NxH3670 for playback. The gamepad can also transmit microphone data to the PC.
• USB VCOM and OTA upgrade function
During the OTA upgrade process, the PC sends the new firmware to the dongle board via USB VCOM. Then, the dongle forwards the firmware to the gamepad. This new firmware will be written to the specified flash address.

App note: Wi-Fi Alliance derivative certification process

App note from NXP giving you an overview of Wi-Fi Alliance certification program and step-by-step procedure of the Wi-Fi derivative certification process. Link here (PDF)

Wi-Fi CERTIFIED™ is an internationally recognized logo of approval for products indicating that they meet the industry agreed standard for interoperability, security, quality and a range of application specific protocols. It ensures the product delivers best user experience.
The Wi-Fi certification program assures tested and proven interoperability among Wi-Fi devices. This certification gives confidence that Wi-Fi product bearing Wi-Fi Certified logo have passed rigorous interoperability requirements.
Authorized Test Labs(ATL) certification is important and most of the time it is the last milestone before the product launch.

Squeezing FPGA memory

Squeezing FPGA memory @ Big Mess o’Wires:

I’m developing an Apple II disk controller that’s based on the UDC disk controller design. The original UDC card had 8K of ROM and 2K of RAM, so it needs 10K of combined memory. The FPGA device I’m using for prototyping, a Lattice MachXO2-1200, has 8K of embedded block RAM and 1.25K of distributed RAM. It also has 8K of “user flash memory”. So will the UDC design fit? It’s close, but I think the answer is no.

App note: Proper resistance measurement test method for Bourns metal current sense

How to Measure low resistance accurately talked through in this white paper from Bourns. Link here (PDF)

Resistance value measurement tests typically use standard multimeters with two measuring wires. This measurement method is suitable for resistance values higher than 10 ohms, but is more prone to inaccurate results when measuring lower resistance values. This is especially true of current sense resistors with resistance values under 100 milliohms. Measuring resistance values less than 1 ohm requires the tester to apply a four-wire (Kelvin) measurement method.

App note: Advantages of sulfur-resistant film resistors

Special type of SMD resistors from Bourns that are resistant to most environmental pollution. Link here (PDF)

In recent years, the long term reliability of film chip resistors in a high sulfur environment plays an increasingly important role in a wide range of market segments such as industrial electronics, IT systems and telecommunications. Sulfurous environments have a negative impact on film resistors by reacting with elements, in particular silver. Sulfide growth can cause resistors to go open circuit.
The critical environmental factors of sulfur pollution are:
• Where oils, lubricants or fossil fuels are used
• Rubber seals, gaskets, grommets or molded coatings of affected material
• Air polluted industrial area or areas containing biological or volcanic gasses

App note: Precautions when measuring the rear of the package with a thermocouple on power devices

App note from ROHM Semiconductors when measuring thermals along exposed pads on power devices. Link here (PDF)

When measuring the rear of the package with a thermocouple, to measure accurately, the thermocouple must be in close contact with the package. A thermal pad for heat dissipation is exposed on the rear side and this thermal pad is connected to the drain due to the design of the package. Since high voltage is applied to the drain, the same voltage is generated in the thermal pad. If you attach the thermocouple here and connect the data logger, a high voltage will also be applied to the measuring instrument. In this case, measurement will not be possible unless the measuring instrument’s rating is higher than the applied voltage.

App note: LED electrostatic breakdown

Very brief reminder from ROHM semiconductors about LED electrostatic destruction. Link here (PDF)

LED products are classified as having a lower electrostatic breakage resistance than other semiconductor products. InGaN devices used in blue and white LEDs are more vulnerable to static electricity than other InGaAlP and GaP (red to yellow-green) devices.

Lab power supply build using old power bricks

Building a lab power supply from old computer power bricks:

Over the years, I have accumulated many used computer power bricks. Although I could just use them by themselves to power other electronics with similar voltage and current requirements, I thought I would combine a few of them together as the input to a linear regulator so that I can make a powerful lab power supply.

See the full post on Kerry Wong’s blog.

Continue reading “Lab power supply build using old power bricks”

Reverse-engineering a low-power LED flasher chip

Ken writes, “How do you make an LED blink? A vintage way is the LM3909, a chip from 1975 that can flash an LED for a year from a single flashlight battery. This chip has some surprising features, such as a charge pump that lets you power a 2-volt LED from a 1.5-volt battery. This IC was designed for simplicity, using just an LED, external capacitor, and battery. In this blog post, I reverse-engineer its silicon die.”

More details on Ken Shirriff’s blog.

App note: MOSFETs withstand stress of linear-mode operation

App note from IXYS talking about MOSFET operating in linear region in application like electronic load. Link here (PDF)

Power MOSFETs are most often used in switchedmode applications where they function as on-off switches. But in applications like electronic loads, linear regulators or Class A amplifiers, power MOSFETs must operate in their linear region. In this operating mode, the MOSFETs are subjected to high thermal stress due to the simultaneous occurrence of high drain voltage and current, resulting in high power dissipation.
When the thermo-electrical stress exceeds some critical limit, thermal hot spots occur in the silicon causing the devices to fail. To prevent such failure, MOSFETs operating in the linear region require high power dissipation capability and an extended forward-bias safe operating area (FBSOA).

App note: Digital inrush controller

App note from IXYS about their unique digital inrush controller using Zilog’s 8-bit Z8F3281 MCU. Link here (PDF)

Digital control allows distinctive solutions to control inrush current in typical AC-DC rectifier with capacitive load by limiting capacitor pre-charge current to a predetermined value at each half sine-wave cycle. Capacitor charge is spread over a number of cycles until capacitor is charged proportion of peak value of AC voltage source. Capacitor is charged according to timedependent pulse train. The pulses are designed in a way to provide substantially equal voltage increment applied to capacitor to keep peak of charging current about the same value at each cycle. Number of cycles depends on capacitor value and charge current. For a given capacitor value which is selected depending on desired ripples amplitude, the charge current is a function of number of pulses and its timing position with respect to rectified sine wave. Detailed algorithm of creating pulse train for Digital Inrush Control is described in the Principles of Operation section.