EFI

[Darrell Norquay]

At 05:37 AM 7/16/96 EDT, you wrote:
>Anyone out there have any solid simple cheap ideas for a 5V power supply for an
>EFI system?  It should have good filtering and be able to supply constant
>output down as low as 8V and as high as 14V.  I hear that transient spikes as
>high as 200V can be seen after the voltage regulator on an engine - so it
>should be immune to these as well. I think I need to be able to drive about
>1 Amp or so. 

>I would like a solution for under $25.  Is this possible?   

You bet.  Depending on how handy you are with electronics, Linear
Technologies, Maxim, and National all make chips to build up a switching
power supply for around $15 for the current output you need.  Extremely
simple.  They will handle inputs from 6V up to around 60V, and for
protection against load dump and other spikes you can just use a MOV and
either a fuse or polyswitch electronic fuse in series with the input.  You
may be able to make the unit even cheaper by phoning Maxim or National and
requesting a couple of samples.  Parts to consider are:

Maxim MAX726-5  2A @ 5V fixed/adjustable
National LM2575-5.0 1A @ 5V fixed
Linear Technologies LT1076 2A @ 5V fixed or adjustable

All you need is the chip, 3 caps, one resistor (or in the case of the
adjustable units, a couple more resistors), a diode, and an inductor.  LT
and National parts, as well as inductors and low ESR Caps (important!) are
all available from DIGI-Key.  I'v used these in several projects now, and
they really couldn't be easier to use.  There are a few tricks to using
switching regulators, so be sure to read the data sheets and app notes
thoroughly before applying solder.  If you need more info, drop me a line.

regards
dn
dnorquay at awinc.com