Gap between layers in PCB

Hello,

I want to know what is criteria for selecting the amount of gap between two layers. Can i make the gap equal?. I have a PCB of Unequal length gap and i want to make it equal length (PCB manfacturer time deduces).

About the bypass capacitor value. IC manufacturer specify a value of

0.01microfarad to .0 microfarad....I think bypass capacitor value depending on the switching frequency....what is the relationship between value of capacitor and switching frequency? any formula has such?

Waiting for reply Regards Praveen

Reply to
praveen
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You have welth of info on Xilinx website. I think it's a XAPP623, XAPP189, XAPP158 ...

Cheers, M.

Reply to
Maki

The gap between two layers is generally equal! ;-) You need to rewrite this paragraph so I can understand it properly. Your English is far superior to my Hindi, but maybe you could get someone to help proof read this for you? Also, explain what kind of signals you're using and what rise time they have.

Be careful here. At higher frequencies the size of the capacitor is the limiting factor to its impedance, not its capacitance. There's bugger all point in using a range of capacitances in an 0402 package, for example. I use a mix of 0805 and 0402 caps, 22u and 1u respectively. If you're a cheapskate, you could use smaller capacitances and it'd make very little difference at higher than 5MHz for the 0805 and 20MHz for the 0402. ( Check out

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) I use the big values because I need to kill the c.1-3MHz noise from my switchers, and a drinking buddy sells ceramic caps! (
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) I'd stick with X5R ceramic, don't use Y5V.

Wait no longer! Best, Syms.

Reply to
Symon

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