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Decoupling

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a thin LED display in SIP module format, much better than TIL311s to visualise your computer buses

Yann Guidon / YGDES 02/10/2017 at 18:234 Comments

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 point

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 point

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 point

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 point

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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