Schematic Opinion - PT2399 Power

[Bio77]

I'm working on a PT2399 project, the layout is pretty dense.  I was looking over the schematic and it seems to me that I can get rid of C24, C25, C36, and C37 since they are tied to the +5V net and C5 and C8 are already handling the filtering.  I just wanted to get some other opinions, in case I'm missing something.  Any help would be much appreciated 

[mauman]

Looks like the 10u caps are reservoirs for the PT2399s, while the 100n caps are decouplers for noise. These are not much of an RC filter unless you add a resistor inline with the 5V bus, but you don't really need that, your incoming +9V is filtered OK.  The 5V regulator will pass along whatever noise it receives, but it doesn't add noise. 

The Princeton data sheet shows a 100n and a 100u on Pin 1 of a single PT2399.  Ideally, decouplers would be right against  pin 1 of each PT2399, so I'd be tempted to replace C5 with a 100u somewhere on the 5V bus, keep C8/C25/C37 (ensuring they're right at pin 1 for each IC) and drop C24/C36.  You save 2 caps and actually get a better reservoir, and for a 5V bus you can find a skinny 100u 16V cap.  The three 100n should be MLCC which are quite small. 

[Bio77]

Thanks!  That's exactly what I was wondering.  If you don't have the caps right next to pin 1, there are just 3 sets of both caps connected to the 5V power trace, which seemed redundant.

[madbean]

Looks like the 10u caps are reservoirs for the PT2399s, while the 100n caps are decouplers for noise. These are not much of an RC filter unless you add a resistor inline with the 5V bus, but you don't really need that, your incoming +9V is filtered OK.  The 5V regulator will pass along whatever noise it receives, but it doesn't add noise. 

The Princeton data sheet shows a 100n and a 100u on Pin 1 of a single PT2399.  Ideally, decouplers would be right against  pin 1 of each PT2399, so I'd be tempted to replace C5 with a 100u somewhere on the 5V bus, keep C8/C25/C37 (ensuring they're right at pin 1 for each IC) and drop C24/C36.  You save 2 caps and actually get a better reservoir, and for a 5V bus you can find a skinny 100u 16V cap.  The three 100n should be MLCC which are quite small.

I agree as well. For a tight layout you can consolidate the electros into one and just add 100n decouplers for all three. It'll work fine.

[Bio77]

Thanks, Brian!