AnsweredAssumed Answered

Additional 300uA drain after flashing

Question asked by Peter Skelly on Apr 13, 2018

Hi everyone,

 

I'm hoping someone can shine some light on some behavior and perhaps offer a solution.

 

After flashing our board which has a STM32L443VC I'm seeing approximately 300uA more of a load from the MCU than I expect, in low power STANDBY the load is approximately 300uA.

 

Removing and reconnecting power clears the problem and I can get down to approximately 17uA in low power Standby which I'm happy with.

 

However, the target is a battery which means once assembled it will always be powered.

 

The problem I'm looking to avoid is updating the firmware with the bootlader as once built there will be no way to completely remove power from the board for the lifetime of the battery.

 

I'm wondering if there is something obvious that I'm missing/ a device to reset or a shutdown process I could follow that will effectively return the MCU to the state it is in when power is removed then re-applied to the MCU.

 

thanks,

Peter

 

UPDATE:

Disappointed not to get any pointers or suggestions, I've solved the problem on my own and want to share the solution as it may help someone else.

 

I initially thought there was some circuitry left powered on after I'd flashed the board and spent some time making certain the Flash, SRAM and a host of other peripherals were all off.

 

After eliminating almost everything else, I tried explicitly switching the DBGMCU unit off before moving to Standby using HAL_DBGMCU_DisableDBGStandbyMode() and this was where the extra 300uA was hiding. I didn't even know that I'd switched it on!

 

Hope this helps someone else.

Peter

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