How do I deploy decouling capcitors in PCB?

[hanzhangusa]

I just want to know what't the rule to deploy capcitors in PCB. What kind of capcitor I should use? I also notice some IC has a couple of VDD and VSS. Should I connent all of them to power or ground?

Thanks a lot

han zhang

 

[IanP]

Typical designs require capacitors with frequencies ranging from 1 KHz to 500 MHz in three ranges:
0.001 to 0.1 µF
47 to 100 µF
470 to 3,300 µF
Try this link for information on decoupling capacitors:
https://hsi.web.cern.ch/HSI/s-link/devices/g-ldc/decouple.pdf

If an IC has multiple Vcc, Vss, Vdd (and so on) .. pins then there is always a reason why it is designed that way. Sometimes you want to separate digital and analog parts , sometimes high and low frequency blocks ..
In most cases you will need to connect them all but these connection must be carefully analysed and in some cases LC or RC low-pass filters will have to be added.

Regards,
IanP

 

[House_Cat]

Here are some places to get information about decoupling:

http://www.interfacebus.com/Design_Capacitors.html#c
http://hsi.web.cern.ch/HSI/s-link/devices/g-ldc/decouple.pdf
**broken link removed**
**broken link removed**[/url]