Doktor Jones
Member
I'm looking at using an LM2940CT to power some LEDs off my car's accessory socket. Now these LEDs are supposed to have some onboard regulation, but I know the car is a very electrically noisy environment so I want the input to the LEDs to be as clean as possible for maximum longevity (when it takes 2-3 weeks to get a replacement off the slow boat from China, replacing them is a nuisance!).
The datasheet shows
1: 0.47µF cap ("Required if regulator is located far from power supply filter") on the input,
2: 22µF cap (Cout must be at least 22µF to maintain stability. May be increased without bound to maintain regulation during transients") on the output. Locate as close as possible to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve.
My questions are thus:
Thanks!
The datasheet shows
1: 0.47µF cap ("Required if regulator is located far from power supply filter") on the input,
2: 22µF cap (Cout must be at least 22µF to maintain stability. May be increased without bound to maintain regulation during transients") on the output. Locate as close as possible to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve.
My questions are thus:
- Would it be beneficial to put a larger cap (e.g 47µF) in parallel with the 0.47µF input filter cap?
- What (if any) would the drawbacks be to using a larger cap (47-220µF) on the output?
- Would there be any benefit to putting a small-value low-ESR cap in parallel with a larger electrolytic cap?
Thanks!