- Tue Apr 14, 2009 11:56 pm
#70690
Hey, all-
Building a low-power data logger. Trying to decide between the internal DCO, calibrated off a 32KHz watch crystal, and using an external crystal. I'll be switching between low-power mode (LPM3) running at 32KHz and high-power mode at 4MHz (LPM0). My thoughts so far:
1) Lowest power consumption: Don't know.
2) Quickest time to come out of LPM3: ~6 microsec for DCO, don't know for external xtal.
3) Least ISR overhead: ISR needed to keep the DCO calibrated so external xtal eliminates this overhead.
4) Board space: DCO wins this one.
I'd appreciate any thoughts folks have, especially other considerations I'm missing.
slaa074 is a good app note discussing a calibrated DCO using a low frequency crystal. And this method is mentioned in several TI docs and other places. Haven't found much about using an external oscillator wrt 1 and 2 above. 3 and 4 seem obvious.
Thanks!
Cheers,
MH
Building a low-power data logger. Trying to decide between the internal DCO, calibrated off a 32KHz watch crystal, and using an external crystal. I'll be switching between low-power mode (LPM3) running at 32KHz and high-power mode at 4MHz (LPM0). My thoughts so far:
1) Lowest power consumption: Don't know.
2) Quickest time to come out of LPM3: ~6 microsec for DCO, don't know for external xtal.
3) Least ISR overhead: ISR needed to keep the DCO calibrated so external xtal eliminates this overhead.
4) Board space: DCO wins this one.
I'd appreciate any thoughts folks have, especially other considerations I'm missing.
slaa074 is a good app note discussing a calibrated DCO using a low frequency crystal. And this method is mentioned in several TI docs and other places. Haven't found much about using an external oscillator wrt 1 and 2 above. 3 and 4 seem obvious.
Thanks!
Cheers,
MH