Doing the math for an SC4517A buck regulator using their datasheet,  
and right off the bat it asks me for something I'm not sure of --  
peak-to-peak inductor current.  I'd think that I should just specify  
the in/out voltages, output current and the output ripple voltage, and  
it would then determine the peak-to-peak inductor current, which would  
then tell me what inductor I would need.

Is this something I can calculate easily?  FWIW, I have noticed that  
when I use inductor-size calculators online (from manufacturer's  
websites and others), the recommended inductor size varies  
significantly.  There's really no consistency here.

Any recommendations on how to approach this?

Some other Q's ...
- What is an acceptable ripple-voltage level or percentage for a PIC  
circuit with analog and digital components.  I'm doing 10-bit A/D  
calcs with internal Vref for ratiometric signals and sometimes  
external Vref (2.5V reference).
- Some inductor datasheets only state Max Current.  Would this be Irms  
or Isat?
- Is it okay to drop in an LDO after a buck converter to really smooth  
things out?  Yes, I'd have to raise the buck output voltage.

Cheers,
-Neil.



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