Hi folks,

I'm looking for suggestions on achieving the lowest power, but accurate, timer to last around 6 months.

It will be at the bottom of the ocean and I have minimal real estate to fit the timer inside an acoustic device so a RTC is out of the question. This device will initially operate for an hour as confirmation on deployment and then sleep (off, powered by the PIC/mosfet) for a period of 180 days. After this the device will be powered up and remain so until its battery supply is exhausted (approx. 2 weeks).

I've looked at DT's Elapsed Timer but sleep command results in havoc with the interrupts it seems, so I'm thinking an SMD 12LF1840 running from a coin cell counting wake-ups from 10 second sleep events could be an avenue. Some quick and dirty code sees about 10uA average consumption using a 4Mhz crystal but speed isn't an issue, but power, size and accuracy is.

Does anyone have any suggestions other than above to offer?

Thanks and regards to all,
Bill