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µController wake up on compare (analog value == pre set internal value)?

Discussion in 'Embedded' started by Ben, Apr 12, 2007.

  1. Yes, that's what I meant.

    If the OP wants to mostly deep-sleep this, (no timers) one solution
    would be a dual approach, of a uA comparitor preset, that then triggers
    an ADC, and the mode would change near the threshold.

    Super low Icc when you know it is comfortably OK, but a faster wakeup
    and check when it's getting marginal....

    Jim Granville, Apr 17, 2007
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  2. I'm not sure that's right. Tresp is typically 150nS (400nS MAX) on a 16f88.
    A somewhat obscure spec called Tmc2ov is 10uS, but that is for a "time from
    comparator mode change to output valid". I think that applies when you dink
    with CMCON and friends.

    Oddly, they don't seem to specify the power requirements of the comparator
    module. Everything else is there (Vref, ADC, WDT, T1OSC etc), just not the
    comparator power requirement value. :-?
    Anthony Fremont, Apr 17, 2007
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  3. Tmc2ov only exists in that one spot in my datasheet. Perhaps it's covered
    in the mid-range manual. I'll have to download one of those someday. ;-)
    Seems I saw it on another part's datasheet. I'll look around and see. I
    may try measuring it, but I'm still fidling with tax junk and some other
    work right now. <go's away for a while> I'm back, I just looked at the
    12F683 datasheet, whoowe that's allot of juice [email protected] is 120uA with both
    comparators enabled. Shouldn't have any trouble measuring that much
    current. I wasn't expecting that much for a couple of comparators.
    Anthony Fremont, Apr 17, 2007
  4. Yes, that looks right for the 18F8520 as well. 150ns typ, 400/600ns
    max (with even more murderous overdrive than typical for sleazy
    comparator specs). The 10usec looks like more of a start-up time.
    No they don't.

    Best regards,
    Spehro Pefhany
    Spehro Pefhany, Apr 17, 2007
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