DM42: The internal view (hardware components)

[jebem]

(02-28-2018 07:09 PM)grsbanks Wrote:  Power consumption when off is in the region of 3uA.

Thanks for your information, Godwin.

Assuming that the DM42 O.S. leaves the STM32L476VGT6 processor in Stop 2 mode with RTC when the calculator is powered off, then only 1.4μA should be accounted for the processor as documented by the manufacturer.
The remaining 1.6μA are consumed by one or more of the other calculator components that will not be totally shutdown during the power off state.

So, concerning the power consumption, here is what we can assume at this point:

1. Assuming a standard 210mAh 3Volt CR2032 battery cell as the power supply.
2. Power ON state, continuous operation: 50h (~2 days) or 4.2mA average.
3. Power ON state, idle: 2000h (~80 days) or 0.1mA average.
4. Power OFF state, battery left inside: 70000h (~8 years) or 3 µA average.

8 years would be a nice lifespan for any coin cell battery if they could survive that long. Maybe they can if the environment conditions are ideal and a good brand advertising expiration dates is chosen. Otherwise battery internal current leakage would usually prevent a CR2032 to maintain its ability to supply current for that long.