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MIDI-Keyboard scanner - error in supply / HF decoupling circuit?

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Sinedup

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Common +5V, common ground, decouplers between?
Hi all.
In a distributor's catalogue selling the 510 Scanner IC, (touch-sensitive MIDI), a simplified schematic of a generic (no brand) keyboard controller is added.
Looking at the way the miniature circuit is drawn, it appears that all 20x 0.1uF caps (decouplers) are connected in parallel between +5V (pin 16) and ground, which appears (IMHO) equivalent to one 2uF mini-disc cap.
Is this normal? o_O

The suppied schematic shows +5V bridged commonly to IC pins:
IC1(16&13), IC2(16&6), IC3(16), then IC4>IC19(16&6).
But then it also shows C3>C21 (0.1uF) bridged commonly to ground on one side, the other leg going to all (p16)'s of IC1-IC19.
It then has C22 (0.1uF) again, between IC1(p16) and ground (parallel with original 'circuit listed' C3 in same position). :confused:

The E510 IC is apparently discontinued (WWW/Google research), but hopefully I can still find one here (RSA) or get a listed equivalent.
Main question is the 'parallel' decoupling caps & C3-C22 conundrum.
Maybe I'm missing the boat but this puzzles my brain-cell. :arghh:

Microscopic circuit from components catalogue was abbreviated and re-drawn using Circuit Wizard.
Original Hi-res scan too large for posting (13Mb) & book is probably copyrighted anyway.
 

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Nigel Goodwin

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Looking at the way the miniature circuit is drawn, it appears that all 20x 0.1uF caps (decouplers) are connected in parallel between +5V (pin 16) and ground, which appears (IMHO) equivalent to one 2uF mini-disc cap.
Is this normal? o_O
Yes, you have a separate 0.1uF on each IC, as close as possible to it's supply pins.

You can't use one larger capacitor, because it can't be close to each IC.
 

Sinedup

Member
Thanks for prompt reply Nigel Goodwin. :woot:
The larger value, 2uF was simply my calculation for 20x parallel 0.1uF caps.
I have 2 synths at home, but keen to build this 'Midi-controller' for the fun-of-it.
 
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