STM32U575: overconsumption in stop2 with LPUART DMAT set

[nicolas]

I have an overconsumption of ~50uA when going into stop2 mode with the DMAT of LPUART set.

Because of the silicon bug (LPUART does not generate DMA requests after setting/clearing DMAT bit), I can't easily clear this flag (the workaround can lead to loss of rx data).

It's probably related to:

https://community.st.com/t5/stm32-mcus-products/hal-pwrex-entershutdownmode-not-working-due-usart-dmarequests-sw/m-p/51367

[Sarra.S]

Hello @nicolas, 

If clearing DMAT is necessary, after the end of DMA transfers, once DMAT is cleared, disable and re-enable the peripheral through the UE bit of the USART_CR1 register. This workaround is acceptable only if the peripheral is not used in receiver mode

[nicolas]

I can't use the workaround because I need to always stay in rx.

Perhaps the best solution is to use DMA for rx only and to use interrupt for the tx which is less time critical.