I'm designing a circuit to run from battery, using a nano without a led (and bypassing the voltage regulator). I want to sleep (PWR DOWN) for 15 or 20 minutes.
I can wake up every 8s with the watchdog, stay awake for ~65ms eating ~45mA (spending in total more than 7 seconds awake during a 15 minute period), or I can try to find a component that can generate an interrupt every 15 minutes - using less power than what the arduino uses awake during the same period.
A simple RTC (PCF8563, powered from the same source as the arduino) would use only 0.25uA, but seems like an awfully complex component for a relatively simple task.
Are there any other low-power components I can use to generate an interrupt after a given amount of minutes? (Needs to be able to work between 1.9v and 3.2v)
The ATtiny85 can also be put into sleep mode for 8s intervals. If you turn off the ADC it uses almost no power, and can be put back to sleep immediately.
I can wake up every 8s with the watchdog, stay awake for ~65ms eating ~45mA (spending in total more than 7 seconds awake during a 15 minute period), or I can try to find a component that can generate an interrupt every 15 minutes - using less power than what the arduino uses awake during the same period.
The arduino nano uses about 45 mA so technically it meets the OP's criteria, unless he decides to change his mind.