LM2940 - Please help with DigiKey parts.

[BigMan73]

I've started a small motorcycle project (AVR and LCD Screen).
Thought I would go with LM2574, now I think LM2940 is better as it is simpler, has protection, and less parts are needed (no coil, schotkey diode)

Could you please recommend on the exact digikey part numbers for the capacitors?
I'm looking for through-hole.

Are these OK?
Cin - 0.47uf
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=493-1885-ND

Cout - 22uf
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=565-2041-ND

Thanks!

 

[tadam]

Hi!

These are 2 different regulators. The one you thought you would go for first is a switcher, and believe me this one is still quite simple.
Anyway if you want to go switching you have to design a decent PCB layout, and probably stick to SMD components.

These part numbers are NOT okay. The capacitors you see are there for decoupling. Surely the datasheet recommends some types?
If they only mention SMD and you really want TH, search for the Panasonic FM/FK/FC series or any other brand which has lower ESR.
The capacitors you found have too high impedance, which certainly isn't suitable for decoupling the IC.

 

[BigMan73]

Going back to LM2574, I was advised to use the HV version.

This is what the spec says:
CIN — 22 µF, 75V
Aluminum Electrolytic

COUT — 220 µF, 25V
Aluminum Electrolytic

D1 — Schottky, 11DQ06

L1 — 330 µH, 52627

I need help with Cin, Cout and L1.
The application is for a motorcycle, not near heat (on handle bars).
This is what I have decided to get so far:
1. Cin - 22uf
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P13142-ND

2. Cout - 220uf
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P5541-ND

3. L1 - 330uh inductor
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=196627&k=52627

Any advice on these will really help me.

 

[tadam]

All wrong components.

Cin/Cout. I told you to search for Panasonic FM/FK/FC, you come up with the EB series???!!!
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P12927-ND
The output cap you could search yourself.
By the way for low values as 22 uF it would be better to use 2 x 10 uF in parallel of ceramic capacitors, much better decoupling, but they are surface mount...

Inductor: too high ESR. You'll want one that lists under its applications "DC/DC converters". Use preferably one that is shielded and take care of saturation current too, eg: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=811-1335-ND

 

[picbits]

I've gone the Micrel route for automotive linear regulators - they don't really care about super low ESR capacitors with exact specifications for the output capacitors. Makes it much easier to design stuff.

Time will tell how reliable they are but have a look at the MIC2951-03YM or similar if you don't need too much output current (they do higher current versions).