Steve Underwood wrote:
Jerry Avins wrote:

Ryan Weihl wrote:

Michael R. Kesti wrote:

Frank wrote:

I have a large board which asks for three power supplies, +3V,
+3.3V and
+-5V.




If I read you correctly, that's four supplies: +3V, +3.3V, +5V, and
-5V.

First two can be easily satisfied with two HP power supplies (each
has its own
GND pin also). Regarding +-5V, can I replace with an HP power
supply set to
10V, -5V pin connect to HP's ground and +5V to power?




No. Doing so would provide zero volts to the board's -5V rail and
+10V to
its +5 rail.

You need four supplies.

will an ATX supply not do?
rw



Maybe not. Compound switchers need a load on the main supply in order
to come up, and the auxiliary supplies aren't always well regulated.

Jerry


They also make more noise than a neo-natal nursery. :-)

If he knows what he's doing, ha can load the 10V supply with a beefy
op-amp connected as a follower to a divider across the rails and ground
its output. If something goes wrong, it can blow the board unless he
uses Zener-cum-fuse protection. There are DC-DC power-supply bricks and
chips that can probably supply all the -5 needed from a +5 supply.

Jerry
--
Engineering is the art of making what you want from things you can get.
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