Re: Inductor arrangement for boosting low-voltage piezo drive

Clifford Heath wrote:

Boris Mohar wrote:
 > Drive an RS232 chip...

I've done that with 40KHz sonar, but I'm worried that the quiescent
current will get me.

So power down the RS232 chip if you are not beeping. If you use the internal shutdown of the MAX220-249... the leakage is 0.1 uA typ.

The device must last for the shelf life of the
2 AA batteries, as it's sealed and will likely be replaced when the
batteries fail. I was actually going to go with a CR2430 or similar
lithium battery, before it was pointed out that it needs an LED to
back up the beeper. What's the lowest quiescent current you can get
in a 3V RS232 driver chip?

It may also be possible or good to use an external switch that powers on your whole circuitry only for a wake-up with a 1 or 0.1 % duty cycle.

In case of alarm this would change to a continuous power-on.


Thomas
.