AW: multiple power supplies in a modular

[Mark Amundson]

My favorite method of +/- supply splits is to use a little larger linear
DC supply like +/- 20 volts and then locally regulate down to +/-15
volts using smaller three terminal regulators on each circuit board.
Most op-amps advertize a 40 dB power supply ripple rejection ratio
(PSRR) so that any post regulator ripple would be further reduced by
bypass capacitors and the op-amps. If you have mixed digital and analog
on board, ensure each type gets its own regulation.

Just remember to park those .1uf X7R ceramics near the op-amp's supply
pins, use 25mil or greater supply traces, and get 10 to 100uf of low ESR
tantalum capacitors across the supply rails after the regulators. Follow
the regulator spec sheets regarding input pin capacitive decoupling.
Beware, all bets are off if the circuits are running at or below
freezing temperatures. Cold caps have less capacitance and more ESR. Low
drop-out regulators are even more finicky of capacitor types and ESRs.

Mark Amundson,

The Dark force of dance wrote:
> Y-ellow Merlin 'n' Y'all.
> > At 02:30 AM 2/6/98 +1100, Merlin Zener wrote:
> >True, but you could always stick a Zener across the cap...

> I spoze y'all were waiting for this but I'm wondering how we're going to fit
> Merlin on the circuit board? Would you mind if we just gag you a bit to
> muffle the screams as we solder you in place? zener's are such noisy things.