[sdiy] Powersupply question

[Harry Bissell Jr]

--- Seb Francis <seb at burnit.co.uk> wrote:

> One other point: it can be a good idea to have a
> diode on the output of 
> each regulator, between the GND and VO, to protect
> the regulator (and 
> tantalum caps) against reverse voltage (obviously
> put the diode round 
> the way it won't conduct in normal circumstances!)


Add another diode with the cathode to the input pin
and the anode to the output pin. If the main filter
cap should suddenly go to ground (usually this is the
biggest cap in the circuit so usually it discharges
slowly)... the regulator can be reverse-biased by the
capacitors on the regulator output (and your whole
circuit).  

There can be quite a lot of total capacitance on the
output (ie lots of current available) and you never
know when a foreign object like a screwdriver might
find its way in there :^P

H^) harry