Power supply for embedded board

[deepgrey]

I am looking around for a power supply that survives engine crank and also supplies 2.5A on the 5v.

Obviously I can get any DC-DC car PSU for this job - but I just want to see if anybody knows a cheaper way as I don't need 80-200watts of power.

[billmee]

You could build a 5v regulator with enough kick to survive cranking.
This is not a DC-DC and should be cheap to do.

Alternatively I've seen plenty of 5v cig lighter regulators ready to go, you just have to find one with the current rating.

[deepgrey]

Does anybody know how much current a slim slot loading dvd drive draws?
Also a laptop hard drive?

I am assuming they are both under 500mA as you can power them from a USB port and USB ports are only 500mA.


Another question - does the carnetix p5v survive engine crank?

[JimmyFitz]

Does anybody know how much current a slim slot loading dvd drive draws?
Also a laptop hard drive?

I am assuming they are both under 500mA as you can power them from a USB port and USB ports are only 500mA.

Your assumption is not valid. That is exactly why so many people have power problems with the portable DVD/CD drives run over USB. Not all USB ports are limited to 500mA. The drive will use MORE than 1A typically. About 1A also for a laptop drive. These aren't specs or ratings but averages I have measured on some systems. The adapter for my optical drive can give up to 2A. If I try to power it from 2 USB ports it flakes out. I have a lappy drive in an external enclosure. The USB port on the front of my desktop PC won't give it enough juice to run. Some ports on my laptop won't and some will. Depends on whether they are current limited to 500mA.

[deepgrey]

I see.

I have a slot DVD drive that can be powered on one USB port - havent had any problems.
Maybe all the drives are differeint - some pull more than others?

So if my mainboard uses 2.5A max and 1.2A normally
the hard drive about 1A
the DVD drive about 1.5A

a 5A PSU should do me.
I have been reading a bit about the LM2678 - which supplies 5v at 5A
http://www.national.com/pf/LM/LM2678...%20Description

Does anybody know of a ready-made 5A PSU based on that design?