App note: Capacitor selection guidelines on LDOs

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They are different kind of capacitors, selection for one capacitor varies depending on application. A good read app note from Analog Devices. Link here (PDF)

Capacitors are underrated. They do not have transistor counts in the billions nor do they use the latest submicron fabrication technology. In the minds of many engineers, a capacitor is simply two conductors separated by a dielectric. In short, they are one of the lowliest electronic components.

It is common for engineers to add a few capacitors to solve noise problems. This is because capacitors are widely seen by engineers as a panacea for solving noise related issues. Other than the capacitance and voltage rating, little thought is given to any other parameter. However, like all electronic components, capacitors are not perfect and possess parasitic resistance, inductance, capacitance variation over temperature and voltage bias, and other nonideal properties.

These factors must be considered when selecting a capacitor for many bypassing applications or where the actual value of the capacitor is important. Choosing the wrong capacitor can lead to circuit instability, excessive noise or power dissipation, shortened product life, or unpredictable circuit behavior.

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Free PCB Sunday: Pick your PCB

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We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Be sure to use a real e-mail in the address field so we can contact you with the coupon.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.
  • PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

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App note: Linear regulators reverse voltage protection

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Various input and output reverse voltage protection method for linear regulators discussed in this app note from ROHM. Link here (PDF)

A linear regulator integrated circuit (IC) is a DC-to-DC buck converter system that reduces a DC supply from higher voltage level to a lower voltage level, thus it requires that the input voltage is always higher than the regulated voltage. Output voltage, however, may become higher than the input voltage under specific situations or circuit configurations, and that reverse voltage and current may cause damage to the IC. A reverse polarity connection or certain inductor components can also cause a polarity reversal between the input and output terminals. This application note provides instructions on reversed voltage polarity protection for ICs.

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Bit-banding explained: A key feature of ARM Cortex-M3/M4

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Yahya Tawil over at Atadiat wrote in to let us know about a corner-stone feature in ARM Cortex-M3 processors called bit-banding:

Writing a portable code is one of the concerns for developers, and while dealing with bit-fields is not standard in all compilers, it is not very advisable to use.
When a feature is available in the hardware itself, you will not have any issues in porting the code from vendor to vendor while both are using the same ARM Cortex-M3 core.

ARM Cortex-M3 features a 1 MB area in SRAM memory called bit-band region. In this region each bit can be accessed individually. To access to bit-band region bits you need to do so via an aliased region, where each word in this region is an alias to one bit in the bit-band region.

More details at Atadiat homepage.

Via the contact form.

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Free PCB coupon via Facebook to 2 random commenters

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Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • We’ll contact you via Facebook with a coupon code for the PCB drawer.
  • Limit one PCB per address per month, please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

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Repairing a 1960s mainframe: Fixing the IBM 1401’s core memory and power supply

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Ken Shirriff wrote a great article describing the repair process of  the vintage IBM 1401 mainframe computer:

The problem started when the machine was powered up at the same time someone shut down the main power, apparently causing some sort of destructive power transient. The computer’s core memory completely stopped working, making the computer unusable. To fix this we had to delve into the depths of the computer’s core memory circuitry and the power supplies.

See the full post on his blog.

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Arduino controlled Dual Mono AK4490 DAC (part 2)

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An update on Arduino controlled Dual Mono AK4490 DAC project we covered previously:

After I was certain that everything related to the software was working the way it should, I designed a “motherboard” that would take care of the following:

  • Accept the STM32F106 board
  • Accept the 3.5″ TFT
  • Accommodate an 24LC256 EEPROM chip, used to store the DAC’s configurable settings
  • Accommodate two sets of I2C signal isolators and I/O expanders
  • Include headers for the encoder, IR receiver, power relay, non-isolated and isolated I2C communication, unused uC pins, etc

See the full post here, Dimdim’s blog.

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CHIP Pro TNC

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Angus Ainslie writes about an open source project a CHIP Pro TNC:

So I finally have a design of the TNC I’ve been working on that I think is ready for release. Initially this started with me wanting a replacement for my mobilinkd and AP510. With feature creep it has turned into much more.
The current board has a VHF radio module, a CHIP Pro computer module running Linux ( NTC calls it gadget OS ) and a Mikrobus slot. I’m currently using the Mikrobus for a GPS module but there are lots of variants.

See the full post on his blog.

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#FreePCB via Twitter to 2 random RTs

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Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

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BML USB 3.0 FPGA interface over PMOD

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An open-source-hardware USB 3.0 to FPGA PMOD interface design from Black Mesa Labs:

Black Mesa Labs is presenting an open-source-hardware USB 3.0 to FPGA PMOD interface design.  First off, please lower your expectations. USB 3.0 physical layer is capable of 5 Gbps, or 640 MBytes/Sec. This project can’t provide that to your FPGA over 2 PMOD connectors – not even close. It does substantially improve PC to FPGA bandwidth however, 30x for Writes and 100x for Reads compared to a standard FTDI cable based on the FT232 ( ala RS232 like UART interface at 921,600 baud ). A standard FTDI cable is $20 and the FT600 chip is less than $10, so BML deemed it a project worth pursuing.

More details at Black Mesa Labs homepage.

Via the contact form.

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