how many caps required for 3.3V rail for 500ma?

[mav1234]

How much capacitance do I need on 3.3V rail with loading of ~500mA?

I have 22uF caps that I can use.

In general, what is a good rule of thumb on how much capacitance required based on a voltage rail and its current value?

 

[matusel]

It depends to the power supply type, for example if you use a ldo linear regulator like LM2931 for 3.3V you certainly need a capacitor greater than 100uF. It depends also to the load type (low/high frequency, resitive - inductive ecc) and to the load regulation perfomance you need. Be more specific pelase.