John Waters wrote...

>For a battery operated circuit, we want the power consumption to be as =
low
>as possible, but if the circuit involves a microcontroller, we will need=
 a
>voltage regulator like the 78L05 or 7805 to keep the 5V stable. Since =
the
>supply voltage is at least 2V higher than the 5V, part of the current =
will
>be bypassed through the regulator, in other words, the regulator =
"consumes"
>some power even when there is no or little current demanding by the
>microcontroller circuit itself.
>
>Is using the regulator unavoidable? What is the usual methods to reduce
>power consumption for a battery operated microcontroller circuit?

7805/78L05 regulators take a fair amount of quiescent current just for
their own internal biasing needs, and for battery operated devices
they're pretty wasteful.

National Semiconductor, Linear Technology, and Maxim all have
micropower voltage regulators that have very low quiescent current
drain suitable for battery operation.  The one I use most often in my
designs is National's LP2951, which takes about a hundred microamps
for internal use.  The nice thing about this part is that it also
provides a handy "low-voltage inhibit" error output which can be used
as a reset signal for microprocessors, etc.

DD

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