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App note: Is the lowest forward voltage drop of real schottky diodes always the best choice?

22 hours 54 minก่อน

App note from IXYS about the pros and cons of different forward voltage drop of real shottky diodes. Link here (PDF)

According to the thermionic emission model, pure Schottky barriers exhibit a forward voltage drop, which decreases linearly as the barrier height diminishes; whereas the reverse current increases exponentially as the barrier height decreases. Consequently, there exists an optimum barrier height, which can minimize the sum of forward and reverse power dissipation for a particular application.
However, discussions with the users of Schottky diodes reveal that they do not search for the minimum of forward and reverse power dissipation but always for the minimum forward voltage drop. Values of reverse current are very rarely asked for. One must know how the Schottky diode is being applied in order to objectively select the most appropriate part.

App note: Voltage vs. output speed vs. torque on DC motors

อาทิตย์, 10/25/2020 - 20:00

App note from Precision Microdrives about DC motor capabilities and their uses. Link here

Why Change Torque?
The most obvious benefit of varying the torque is to maintain a constant speed when the motor’s load varies, keeping in mind the interdependent nature of speed, torque, and voltage.

Although this example may be outdated, audio cassettes are a great way of explaining how some applications need to vary the torque to match a changing load. As the cassette plays and the audio tape moves from one spindle to the other, the driving motor will experience a change in load. However, the playback must remain at a constant speed throughout – otherwise the audio pitch would be affected.

Why Change Speed?
The ability to vary motor speed whilst maintaining a steady torque is essential to many applications for a variety of reasons.

An example of an application that requires a variable speed and steady torque is an audio CD player as it is commonly observed that the CD will rotate faster at certain points than others. This is because the information is stored in spiralled circular tracks on the disk and the length/circumference of the track is directly proportional to the amount of information stored on them. This means that the speed must be decreased as the laser is reading from the outermost tracks because there is more information per revolution. Inversely, the speed is increased as the laser reads from the innermost tracks as the spiral circumferences are smaller and therefore contain less information per revolution.

ClockSquared Mini

พุธ, 10/21/2020 - 06:59

Willem has been working on a tiny word clock, the Clocksquared Mini:

Summer break is here, and with some time to spare I decided to challenge myself with a project that I call “Clocksquared Mini”. It is Clocksquared, but in a tiny wristwatch package. This gives rise to a major challenge, as everything has to be shrunk down approximately ten times from a 300x300x50 mm to an approximately 35x35x7 mm package. Moreover, running everything off a tiny battery whilst maintaining an acceptable battery life also turns out to be quite difficult.

Project info at willemm.nl.

Designing a Memory/IO (ETA-3400) addon for the ET-3400 trainer

อังคาร, 10/20/2020 - 06:59

Dr. Scott Baker designed and built an ETA-3400 Memory/IO accessory for the vintage Heathkit ET-3400 trainer, that is available on GitHub:

I’ve always wanted one of these Heathkit microprocessor trainers, and finally one caught my eye on eBay and I pulled the trigger. The basic interaction with the trainer is through the onboard keypad and LED displays, but Heathkit also made an accessory that added additional ROM, RAM, serial port, and a cassette interface.
This allowed you to use a machine monitor over the serial port, and even featured a Tiny Basic interpreter in ROM that allowed the trainer to be programmed in Basic.

See the full post at smbaker.com.

Check out the video after the break.

App note: TQFN package thermal pad via design guide

จันทร์, 10/19/2020 - 00:20

TQFN footprint pad via design guide for proper thermals from Diodes Incorporated. Link here (PDF)

TQFN packages have exposed pads to provide excellent electrical grounding paths to the PCB and transfer the device heat through thermal vias on the PCB thermal landing to the internal copper planes. In order to maximize the removal of heat from the package, the number of vias, the size of the vias, and the construction of the vias must be considered for the thermal landing pattern. The exposed pad must be soldered down to ensure adequate heat conduction from the package.

App note: Understanding thermal resistance in the real world

อาทิตย์, 10/18/2020 - 20:00

App note from Diodes Incorporated about thermal resistance and how to manage them in real world scenario. Link here (PDF)

There can be significant differences between the thermal characteristics stated on a device datasheet and what actually happens in a realworld application. Semiconductor manufacturers usually provide thermal resistance values for Junction to Case (RθJC) and Junction to Ambient (RθJA); although these are extremely useful parameters to estimate a device power handling capability, there can still be a disconnection between those figures and reality.

App note: Processing instructions for mounting of through-hole LEDs

อาทิตย์, 10/11/2020 - 20:00

Do and don’ts when mounting through-holes LEDs, app note from Vishay. Link here (PDF)

Through-hole LED cases usually consist of epoxy casting compounds with duroplastic properties. It is in the nature of things that optical semiconductor devices require transparent materials with the best possible optical features. Unlike standard IC mold compounds, which use reinforcing fillers like class fibers to achieve better mechanical stability, these optical materials must not be filled. In addition, due to the very small component dimensions, the wall thickness of the casted resin body is also small. All this results in some special aspects regarding mechanical stability during the soldering process to be considered for the processing of leaded LEDs.

Nano sheet factory

พุธ, 10/07/2020 - 06:59

Building a nano sheet machine @ Fablab RUC

Sometimes even very expensive and well build equipment breaks. This recently happened to researcher Biljana Mojsoska, a chemist at Roskilde University. She was working with nano sheets, an anti-bacterial coating for medical surfaces, as her machine stopped working.
The fact that such equipment can be so expensive to replace or repair triggered Jakub Klust and Bo Thorning at Fablab RUC. Could they build a machine with the same functionalities, using the equipment available at FabLab RUC? Would it be possible to build a much cheaper and easier to fix version of Biljana Mojsoska machine?

See the full post at fablab.ruc.dk.

Thermocouple meter and datalogger

อังคาร, 10/06/2020 - 06:41

Thomas (LA3PNA) has designed and built a thermocouple meter, that is available on GitHub:

I have designed a thermocouple meter for use for obtaining temperature readings from thermocouples. Its used together with the thermal chamber described elsewhere on this site. The design is done primarily as a programmable instrument, but it has a OLED display, so it can show the current temperature. The programming uses SCPI, the same type of programming strings that most newer (1990 forward) instruments use.

See the full post on RF and electronics blog LA3PNA.

App note: New reliability assessment practices for Tantalum Polymer Capacitors

จันทร์, 10/05/2020 - 00:00

App note from KEMET on their new suggested testing for Tantalum polymer capacitors. Link here

Tantalum polymer capacitors are expanding their market share in the commercial world because they offer superior electrical performance (primarily much lower ESR), have outstanding reliability, and display a more benign failure response than the incumbent MnO2-cathode tantalum capacitor technology. It is natural that engineers want to use this new technology in high-reliability applications.
However, a key reliability assessment tool for MnO2-cathode tantalum capacitors – Weibull grading per MIL-PRF55365 – is often ineffective when applied to tantalum polymer capacitors. Because this well-established tool often proves ineffective, a new reliability assessment strategy is needed and has now been developed by KEMET.
The basic principles behind the Weibull grading technique are reviewed, as are the reasons why it is often ineffective when applied to tantalum polymer capacitors. Then a new reliability assessment strategy for tantalum polymer capacitors is described. Special emphasis is placed on differences in the typical time-to-failure responses of tantalum polymer capacitors versus MnO2-cathode tantalum capacitors during this discussion. Finally, an example is given of successful use of this new reliability assessment strategy in a real-world high-reliability application.

App note: Moving capacitors for mobile phones to the dashboard

อาทิตย์, 10/04/2020 - 20:12

This application note introduces polymer electrolytic technology, the electric performance of these parts, advantages relative to other capacitors, and how the commercial-grade product was improved to pass the stringent AEC-Q200 guidelines.

KEMET app note link here

Tantalum polymer capacitors are popular in many decoupling applications including high performance DC to DC converters. This created a perfect fit for polymer capacitors in telecom and industrial high performance applications. Now the automotive segment is showing an increased demand for these type of capacitors for use in infotainment and advanced driver assistance systems (ADAS). Most automotive applications require passive components to be qualified to the Automotive Electronics Council’s AEC-Q200 Stress Test Qualification for Passive Components. KEMET Electronics has addressed this need by developing new processes and materials to offer the market’s first polymer electrolytic capacitors qualified to AEC-Q200.

Connect a Commodore with thermal printer

เสาร์, 10/03/2020 - 06:41

Connect a thermal printer to vintage Commodore computers using the IEC bus @ smdprutser.nl

Since a couple of months I have fascination for vintage computers like Commodore or Nintendo. I’m in the process restoring and pimping a Commodore SX64 and realized I did’t have a printer for it. After all it is an executive machine and how do I otherwise print my quotations and invoices? The solution was in a thermal printer I had lying around for years without a real purpose.

App note: Paralleling linear regulators made easy

จันทร์, 09/28/2020 - 01:04

Various configuration of linear regulator for parallel operation discussed in this technical article from Analog Devices. Link here

Linear regulators provide a simple, low noise solution for dc-dc regulation. However, at higher VIN-VOUT differentials the low efficiency and high power dissipation of linear regulators limits the amount of output current that can realistically be delivered. Connecting multiple linear regulators in parallel spreads the load (and the heat) over several ICs, increasing the useful range of output currents a solution can deliver. However, connecting linear regulators in parallel is not always straightforward.

App Note: Optimizing CAN node bit timing to accommodate digital isolator propagation delays

อาทิตย์, 09/27/2020 - 20:00

Adding robustness by digital isolation and compensating for propagation delays to CAN network presented in this technical article from Analog Devices. Link here (PDF)

Controller area network (CAN), standardized under ISO 11898, is widely used in industrial and automotive applications. CAN protocols such as DeviceNet or CANOpen rely on the built-in error checking and differential signaling. Galvanic isolation can further enhance robustness, offering immunity to high voltage transients at a cost of added propagation delay. The optimal configuration of CAN nodes can allow the maximum data rate and distance even when isolation is present.

App note: Impedance characteristics of bypass capacitor

จันทร์, 09/21/2020 - 00:00

App note from ROHM Semiconductors about different type of bypass capacitors impedance and some tip when replacing them. Link here (PDF)

There are various types of capacitors. If you select parts only based on their capacitance values, the requirements for bypass capacitors may not be satisfied, leading to malfunction of devices or nonconformity to standards. This application note focuses on the impedance characteristics of capacitors, and explains cautions for selecting bypass capacitors.

App note: BA1117 dropout voltage

อาทิตย์, 09/20/2020 - 20:00

App note from ROHM Semiconductors about linear regulator dropout voltage. Link here (PDF)

The dropout voltage is the difference between the input and output voltages that is necessary for the stabilizing operation of a linear regulator. When the input voltage approaches the output voltage, stabilizing operation cannot be maintained and the output starts dropping in proportion to the input. The voltage at which this situation starts, i.e., the difference between the input and output voltages that is necessary for the stabilizing operation, is referred to as the dropout voltage.

Supercapacitor uninterruptable power supply (UPS) for Raspberry Pi

ศุกร์, 09/18/2020 - 06:59

smbakeryt built a couple supercapacitor uninterruptible power supply (UPS) prototypes for his raspberry pi projects:

For my Convergent restoration, I decided to build an RASCSI to replace some failing SCSI hard drives. The RASCSI is a SCSI emulator built using a raspberry pi. Problem with these types of emulators is that if you carelessly power off the host computer (which was a perfectly acceptable thing to do back in the 80s), you end up also unsafely shutting down the pi — which can cause corruption of the SD-Card, loss of in-memory data, etc.
Back when I built David Gesswein’s MFM Emulator, he included a supercapacitor UPS that provided power just long enough to safely shut down a beaglebone. I figured the same thing would work for a raspberry pi.

Project info at smbaker.com.

Check out the video after a break.

Reverse-engineering the first FPGA chip, the XC2064

อังคาร, 09/15/2020 - 06:56

Ken has written an article on reverse engineering the first FPGA chip, the XC2064:

The FPGA was invented by Ross Freeman1 who co-founded Xilinx2 in 1984 and introduced the first FPGA, the XC2064. 3 This FPGA is much simpler than modern FPGAs—it contains just 64 logic blocks, compared to thousands or millions in modern FPGAs—but it led to the current multi-billion-dollar FPGA industry. Because of its importance, the XC2064 is in the Chip Hall of Fame. I reverse-engineered Xilinx’s XC2064, and in this blog post I explain its internal circuitry (above) and how a “bitstream” programs it.

See the full post on Ken Shirriff’s blog.

App note: RS-485 communication link vs. the electric fence, A demonstration of RS-485 EMC robustness

จันทร์, 09/14/2020 - 01:40

Analog Devices’ RS-485 robustness demonstration by direct application of HV transient to the communication line. Link here

Industrial and instrumentation applications (I&I) require transmission of data between multiple systems, often over very long distances. The RS-485 bus standard is one of the most widely used physical layer bus designs in I&I applications. Applications for RS-485 include process control networks, industrial automation, remote terminals, and building automation such as heating, ventilation, air conditioning (HVAC), security systems, motor control, and motion control.

In these real systems, lightning strikes, power source fluctuations, inductive switching, and electrostatic discharge can cause damage to communications ports by generating large transient voltages. Designers must ensure that equipment does not just work in ideal conditions but also works in the ‘real world.’

App note: Using ESD diodes as voltage clamps

อาทิตย์, 09/13/2020 - 20:00

App note from Analog Devices on improving robustness of an amplifier by determining and mitigating internal ESD diode clamp electrical overestress. Link here

When external overvoltage conditions are applied to an amplifier, ESD diodes are the last line of defense between your amplifier and electrical over stress. With proper understanding of how an ESD cell is implemented in a device, a designer can greatly extend the survival range of an amplifier with the appropriate circuit design. This article aims to introduce readers to the various types of ESD implementations, discuss the characteristics of each implementation, and provide guidance on how to utilize these cells to improve the robustness of a design.