On Thu, Jan 31, 2002 at 04:34:20PM -0000, zantos wrote:
> I could do with some help here..
> I am driving a small thermal printer with cutter and need a 7.7v @5A for
> 3mS. I thought I might use an LM338 voltage reg stright out of the
> ST-Thomson book. But I'm not happy with that route.
> Any suggestion where there is a better approach?

Why don't you like that approach? It's the least complicated.

The second least complicated is using an LM317 along with a PNP pass
transistor.  The benefit will be that you can use a beefier transistor that
can pass more than 5A, and that the LM317 can share an amp and change of
the load. Check out the section labeled "LM317T Voltage Regulator with Pass
Transistor" here:

http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

Other ideas include building a simple switcher (LM2574) driving a
external pass transistor (probably a low Rds(on) p-channel MOSFET).
It will eliminate the heat dissapation issue due to being a switching
regulator. Be careful about output capacitors or you'll get a great
oscillator. Check the ESR required.

But unless you have a really good reason, the simplest solution probably
is the best.

BAJ

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