12F629 @ 32kHz - driving me barmy!

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

You might try turning the refrence on and off as needed it can be configured on the fly. Same for the comparitor. Brownout is not going to help you.

dazza · Guest

Hi,

Thanks everyone.

PCM - yes it was because of all those features I had enabled. After disabling them, I'm down to about 30uA.

I do not have a regulator - instead im running directly off the CR2032 battery.

I shall have to put some sort of low-batt detection on here... I was going to use the on-chip comparator but that takes too much juice to be left on permanently.
So my next question is, can I turn the comparator on, do a batt. check and then turn it off again, say once every hour??? or does it need to be left on permanently?
Im thinking that a low batt. condition is when the voltage is 2.1V or less. If 2.1V, simply go to sleep.

Is there an on-chip voltage reference which will still be reliable at 2.1V?
Or do you think it's better to have an external ref. / op-amp configuration to detect low batt. at these low voltage levels?

Regards,
Darren

dbotkin · Joined: 08 Sep 2003 Posts: 197 Location: Omaha NE USA

Yes, you can turn on the comparator (or ADC, or whatever else you need) just while you need it, then turn it back off.

Bear in mind that the internal Vref is no more than a voltage divider referenced from Vdd... so the internal reference won't do you any good for detecting low battery. You'll need an external Vref.

Dale

willie.ar · Joined: 21 Jan 2004 Posts: 15 Location: Argentina