I've a circuit which inputs a slowly changing analog sine wave to a pin, where the AC (comparator) level compares it.
I'd like ideally to stick the chip into powerdown mode based on this pin being zero for a timeout, but reading into the datasheet the AC won't function. There's a low-level pin interrupt which may work but it'll be low level when I enter power-down - will it need to cycle high before hitting low again to fire the interrupt or immediately fire?
Alternatively I think the next best thing is to use Idle mode but switch the MAIN_CLK to use the 32KHz internal, which will allow the 20MHz internal to shutdown and the AC to continue working. The 32KHz is always running as it's fed into the RTC PTC. Although all other peripherals are disabled (CTRLA) I've read that feeding any CLK_PER into them does actually waste a bit of power.
How's my thinking?