Subject: Re: [Ace] ACE Clock Synchronization Design Team Conference Call

From: Peter Aldworth <[email-masked]>
Date: Thu, 23 Jun 2016 07:20:28 +0000

All,

Just following up from our discussions in the call on 20th June:

Typically an off-the-shelf commodity MCU standby power draw (with RTC
enabled) would be less than 2uA at the battery terminals (including
power draw of constantly running 32kHz crystal oscillator).

So using a 150 mAh coin cell (with a rated 5 year self discharge time)
with an MCU in a low power mode (RTC running) you would theoretically
get greater than 8.5 years of battery life - ignoring self discharge.
Using a "state-of-the-art" low power MCU you might get this up to 34
years (again ignoring self discharge). Basically standby power draw is
not a limit here.

The above assumes a commodity 32768 Hz watch crystal which gives 20ppm
clock accuracy "at room temperature". Expect a volume cost for the
crystal in the range $0.10-$0.25. If you need better timing/temperature
stability then it could become significantly more expensive in both BoM
cost and power consumption.

Regards,

Peter Aldworth

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