Okay so I'm not an electrical engineer so you may have to dumb this down for me a bit.
I'm looking at using the LM2940 regulator for an automotive application. Datasheet suggests using a 22uF tantalum cap on the output... tantalum seems a lot more expensive than ceramic or aluminum electrolytic. The data sheet addresses this and says,
It is important to note that for most capacitors, ESR is specified only at room temperature. However, the designer
must ensure that the ESR will stay inside the limits shown over the entire operating temperature range for the
design.
For aluminum electrolytic capacitors, ESR will increase by about 30X as the temperature is reduced from 25°C to
−40°C. This type of capacitor is not well-suited for low temperature operation.
Solid tantalum capacitors have a more stable ESR over temperature, but are more expensive than aluminum
electrolytics. A cost-effective approach sometimes used is to parallel an aluminum electrolytic with a solid
tantalum, with the total capacitance split about 75/25% with the aluminum being the larger value.
If two capacitors are paralleled, the effective ESR is the parallel of the two individual values. The flatter ESR of
the tantalum will keep the effective ESR from rising as quickly at low temperatures.
So what about ceramic caps? How do they compare?
This is for an automotive application so theoretically it can get pretty cold in the car... it doesn't really mention anything about hotter temps...
It seems that their cost effective approach of capacitors in parallel would still require a fairly expensive tantalum cap anyways (although smaller).
Any guidance would be appreciated! Thank you
