Hi everyone!

I have a couple (or few couples?) of problems. How to begin...

So, in one my application I need a kind of voltage source switch.
Let me explain, I'm putting up a circuit (controlled by a PIC, obviously)
that have to operate from the telephone line, when active, and automatically
switch to battery power if the line fails or the circuit is in standby mode.
All this have to be VERY low power, so that the battery do not discharge
too fast (few months min.). I intendend to use a voltage comparator(s) to do
this, then the problem of reference voltage come up. I tried to use a zenner,
but it draws too much current for stabile operation. I found some voltage
reference circuits, but they need too much current/voltage to work properly.
Can I trust the battery for a stabile voltage? Has anybody any suggestion
regarding voltage references (low power 50uW?) or, better, about a
"supply controller"? The entire circuit is working at 3.0-3.3V and draws
6mA max. when functioning and about 25uA when in stand by.

Thanx in advance,


Mauricio CULIBRK

ARNE Computers d.o.o.
Cesta v Gorice 38                                   Phone:   +386 61 1233-171
61111 Ljubljana                                     Fax:     +386 61 1233-488
Slovenia                                            E-Mail:  mauricio@arne.si
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