[STM32WLE5CC] Firmware behavior according to power

[BHwan.2]

Currently, we are using the STM32WLE5CC MCU.

Some MCUs do not operate normally when the same firmware is inserted into several MCUs. (Abnormal current, delays in Uart log output, RF is not transmitted)

If a higher voltage (4.4V) than the MAX operating voltage (3.6V) is applied to these MCUs, it operates normally.

I wonder why this problem appears

If you have such experiences and solutions, please let me know.

[Andrew Neil]

"If a higher voltage (4.4V) than the MAX operating voltage (3.6V) is applied to these MCUs, it operates normally."

You mean they all work fine at "too high" voltage, but are flaky at the datasheet-specified maximum?

How are you measuring the 4.4V - is that directly at the MCU pins?

Have you checked the power supply on an oscilloscope?

(needs to be done at the MCU pins)

Remember that radio transmitters & receivers have very "peaky" current demands - a poor power supply and/or poor PCB power routing can result in the supply "dipping" during current peaks.

That can certainly lead to "erratic" behaviour...

By running the nominal supply "too hot", it could be that your "dips" (just) manage to remain within spec...