STM32WLE - IWDG in Standby Mode

[RLind.3]

Hi there,

I am using an STM32WLE and I am trying to reduce my Standby mode current consumption. I am currently drawing around 800nA, while the datasheet says I should be drawing about 450nA. One potential cause of excess current is the LSI running for the IWDG (~100-150nA). I have set up the option byte IWDG_STDBY to freeze the IWDG in Standby mode. Does this option byte disable the IWDG (and therefore the LSI) in Standby mode or just freeze the counter?

Some of the IWDG registers in RM0461 say they are reset by Standby mode (KR, RLR, WINR), but not others (SR). The PR register doesn't specify. Does this mean the IWDG continues running through a Standby mode exit? And if so, does it lose the previous set up?

Any help or clarification would be greatly appreciated. :smiling_face_with_smiling_eyes:

Thanks,

Rebecca

[Benoit MARCHAND · Accepted solution]

Hello,

IWDG_STDBY will freeze the counter. If you don't need LSI for other blocks (like RTC) you have to stop it independantly (through RCC_CSR.LSION register).

KR, RLR, WINR are reseted when entering Standby as a functionality, linked to their use by the FW.

BR,

Benoit

[RLind.3]

Hi Benoit,

Thanks for your response. Could you please clarify the following points?

• Does the IWDG continue running through a Standby reset?
• Can I disable the LSI while the IWDG is running? What behaviour will this cause?

Thanks,

Rebecca