From the data sheet,

a) 22uF is the minimum amount of capacitance to use
b) no upper bound on total capacitance
c) both low and high esr can cause oscillation
d) a mix of 75% aluminum electrolytic with 25% tantalum gives the 
right 	   esr

So I would try 22uF tantalum and 100uF Al electrolytic.  Depending on 
your application, you might also get by with only using tantalum caps. 
In that case, you probably would want to use double the recommended 
minimum of 22uf so might try 47uf.

Problem areas would tend to be using *only* Al electrolytics or *only* 
low esr ceramics.

Good luck!


Josh Koffman wrote:
> Hi all. I'm working on a little circuit that will live in my car...so
> I need an automotive voltage regulator. Cost isn't really a huge
> concern since I only need a couple. I know many people like the LM2940
> though I recall a post about the capacitors it needs being expensive.
> What I'm unclear on is whether that was for no load regulation or if
> the low ESR caps are always needed.
> 
> I'm not so great on power supply design so any help would be awesome!
> 
> Thanks!
> 
> Josh

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