Decoupling

Franck just spotted a pretty fumble : I have overlooked the bulk capacitors before and after the LP2981.

I think I assumed that the voltage stability was not critical but usually I am very generous with capacitors.

The other problem is : is there any room left ?

Discussions

K.C. Lee wrote 02/10/2017 at 18:40

You can replace all the 0.1uF decoupling caps with 1uF ceramic caps as a way to increase the bulk value. Leave the 0.1uF in if there are any high speed chips.

For low frequency work (as in the 10-20MHz or below), it won't make much of a difference.

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K.C. Lee wrote 02/11/2017 at 22:50

Sorry gave you bad advice. Turns out that the LP2981 doesn't like ceramic caps because of their low ESR. So you might have to find some small tantalum/electrolytic caps for the output bulk caps.

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Yann Guidon / YGDES wrote 02/12/2017 at 00:42

I supposed so, thanks for confirming ! I'm running out of space...

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K.C. Lee wrote 02/12/2017 at 04:13

The pin out of LP2981 is the same as Microchip MIC5245 which is compatible with ceramic caps. There might be other parts that are compatible too.

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Resuming

PCB rev.2

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