Don't know if it'd work, but since you're ordering parts anyway
would a regulated charge pump work? I assume you're not using
the control lines; if you diode-or them together with maybe some
small resistors to limit & balance the load and set 'em high, they
oughta be good for 30-40ma, and if you're using a DAC it shouldn't
draw nearly as much power as an R-2R ladder...
It's often done with RS-232 gizmos, but I don't see why it wouldn't
work on the Parallel port as well.
Just a thought (and probably not a good one...)
mike
Original Message:
---------------------------
Date: Tue, 4 Jul 2006 18:35:37 +1200
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Subject: Powering (or not) a parallel-port-attached DAC (was Re:
Vector Imagery)
On 7/4/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Obviously you might well not be able to do this. In
which case, you
either have to buffer the port lines (to reduce the output impedance
there) or add a buffer amplifier on the analogue output. Either solution
involves active components that need power.
I know that the "right" way to do it involves active components...
given my 95% success with passive components, I was hoping to squeak
by. If I could get power and data from the same source (see below), I
wouldn't be quite so picky.