Components


I have been very busy at the lab lately, too busy to update ublog regularly, and this set of formulas from Gamma Instruments has saved me a bit of trouble. Several air core inductor designs are outlined which allow you to make your own custom inductor, within reason, if you need to test something and you don’t have the part on hand. Typically, the inductance values will be modest, however, it is much easier to make an inductor yourself than a reasonable capacitor. Just think of all of the folding!

( pancakewheel )

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I recently read a statement somewhere along the lines of “you always want low equivalent series resistance (ESR) capacitors in your design” which got me thinking about ESR and capacitors in general. The truth of the matter is that you do often want capacitors with moderate ESR (>10 Ohms) for bypass applications, especially in voltage regulation circuits. The main reason is that the capacitor introduces filtering (a zero) into the circuit just through its own capacitance and series resistance, and this filtering can be used to stabelize the feedback of a voltage regulator and prevent ringing/oscillations. AN-1148 is a great application note from National semiconductor that gives an overview of feedback in voltage regulation and frequency domain analysis.

Once the concept of adding a zero to the frequency response of a circuit is clear (see this app note if it is not), it should be apparent that this is exactly the reason why designers put several bypass capacitors in parallel when decoupling a complicated integrated circuit. The IC injects a known set of frequencies into the power system and the designer tries to use each of the capacitors, with a unique zero, to try to filter out each frequency individually. This works well for circuits with precise clocks, however, an RC oscillator can have plenty of drift so it would be advantageous to use capacitors with higher ESR which lead to lower Q values and broaden the range of frequencies which they filter out most effectively. This follows the notion that you should not use high quality components to filter a low quality circuit, all components should be of the same quality.

( an-1148 )

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I have many AS and LS series logic gates lying around, so I figured that I would image some as they would be more instructive than looking at the latest CPUs coming out of Intel. I have a few more lined up so please comment if you want me to follow this reasoning. Today’s subject is a hex-inverter, the 74AS04. Below are images of the whole chip and a blowup of the top-right inverter gate.

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Now that I have everything unpacked, the IC Friday program can resume. Today’s a nSpire processor sent in by Travis Goodspeed. Two notes of interest are the prominent LSI LOGIC badging and the dual CHIPIDEA cores. The model number looks like CI12320, but that is not listed on their page.

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Today’s IC Friday is another reader-submitted chip. This is cryptoworks six-pin smartcard. The only writing on it is “TUBEAV A”.

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Today’s entry is an old memory chip from Mitsubishi, the M5K4164. This is another chip submitted by a reader, again, all the way from Iceland.

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Today’s IC Friday entry is the 8bit AVR micro from Atmega. This chip was sent in by a reader, all the way from Iceland.

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Found the NASA Workmanship Technical Committee website recently while looking at ESD standards. Not much to say about it beyond that it is a good place to look around for general technical information on electronics. Their pictorial inspection reference for examining flight hardware is pretty nice too.

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This weeks entry is the 20-bit delta-sigma DAC from TI.

dac1220-10x-stitch.jpg

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lmc6042-4x.jpg

Today’s entry is the LMC6042 dual-op amp from National Semiconductor. The layout of this device is a bit different from a standard op-amp due to the inclusion of some periodic components. It can also be noted that this die is mostly the same as the LMC6044 except that the two op-amps on the bottom-right side of the chip don’t have most of the metal deposited.

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