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The Master
- 3rd January 2011, 17:03
Hi, I'm trying to design a PCB for an AT91SAM7S chip (AT91SAM7S Datasheet (http://www.atmel.com/dyn/resources/prod_documents/doc6175.pdf)). At the top of page 13 it says to use 100nF NPO and 4.7uF X7R caps in parallel for VDDIN. I can't find either of those on Rapid. I can find the 100nF as an X7R and both values as other types of caps. Could I use some of these others instead?

The main board will have a 5V regulator followed by a 100uF electrolitic cap. The power rails will be connected to the CPU board (the one with the AT91SAM7S chip on) which will have a 3.3V regulator before connecting to VDDIN.

mister_e
- 3rd January 2011, 20:21
I wouldn't worry that much myself... Any decent multilayer Ceramic or Tantalum would do. Even a ceramic disc + Electrolytic combo would "do" the job. This is just decoupling caps after all.

100uF at the output of your regulator is way too high IMO.

The Master
- 4th January 2011, 20:54
The 100uF is mainly for smoothing the DC ripple.

Thanks. I'll experiment with some other types