PIC power consumption & power saving

[amcfall]

SOrry to bring this up again, but I am woking on a little board and I'm curious about it's power consumption (not all that important, mostly just for my information). The app is as follows:

12F683 w/ nanowatt technology
two inputs (A4 and A5) using internal pullups, connected through momentary switches to ground
one input from host PC on A0
using hardware PWM, 200Hz on A2
internal pullup for _MCLR enabled
other pins N/C
internal OSC @ either 2Mhz or 32Khz

When the enable line from PC goes low I switch the oscillator to 32khz, which brings me down to about 113uA. I then switch all pins (other than enable, A0) to outputs, disable port a pullups and set the outputs low. I then enter sleep, and wake up with the WDT. When it's sleeping it seems to draw about 90uA. Seems like it could be a lot lower, from how I'm reading the datasheet. However I read somewhere that using the internal oscillator draws more power than an external XTAL. As I said it's not critical, more of a how low can you go kinda thing.

Avery

[MikeValencia]

Try switching to an external oscillator, and you'll probably halve your power consumption. At the uA you're at, you can probably outlast the shelf life of an idle Energizer. I don't know the exact numbers, but i do remember that internal oscillators do burn up significant current when you want to hover in the <100uA consumption range.

[Ttelmah]

When asleep, the oscillator is stopped. The internal oscillator draws more current when awake, but not when asleep.
However it is _critical_, to turn off all peripherals. The PWM, should be stopped, the ADC, should be stopped, the comparator disabled etc.. The 'worst' one, is the brown-out detector, and the internal voltage reference, which can each draw around 60uA...
You should be able to get current figures below 35uA, with care.

Best Wishes

[amcfall]

[amcfall]

After changing the fuses it's at around 4uA.

Thanks

Avery

[Ttemah]

That actually sounds slightly better than I'd have expected, unless you are running on a lower Vdd?. The watchdog alone, has a 'typical' current of 8.4uA at 5v, but drops to 2.7uA at 3v. The battery life should be pretty impressive at this level. :-)

Best Wishes

[amcfall]