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From: Spehro Pefhany
Subject: Re: PIC controlled variable power supply
X-Newsreader: Forte Agent 1.93/32.576 English (American)
Date: Fri, 17 Jan 2003 14:50:05 GMT
NNTP-Posting-Date: Fri, 17 Jan 2003 09:50:05 EST
On Fri, 17 Jan 2003 00:37:07 -0700, the renowned Jim Drew
>I am looking for a solution to a problem. I need to construct a power
>supply that can be varied from 5 volts to 8 volts, controlled via PIC.
>The output must be able to handle at least 500ma (preferably 1 amp).
>I have thought of an adjustable voltage regulator like a LM317, but the
>adjustment is on the ground side and the PIC can only sink 25ma of
>current. If there is an inexpensive voltage regulator with some sort of
>external adjustment, that would probably work. I have 8 output lines
>that I could use an R2R ladder to generate the adjustment voltage.
>Any thoughts on better methods??
Use your PWM output or R-2R ladder to generate a voltage. Buffer the
voltage with a unity-gain op-amp and feed it to the adjust pin on an
LM317 as so.
0---- IN Out -------x----->
This gets you short circuit and overtemperature protection, and
the cost will be very low.
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