STM32 ADC - power supply error - what are the consequences?

[Oliver 2017]

Posted on July 31, 2017 at 13:56

I made a mistake when designing a PCB for an STM32L152RE (the 64 pin variant) - I had thought the VDDA pin was the voltage reference for the ADC, so I wired this to an accurate 3V reference supply. My main supply is 3.3V (connected to the other four VDD pins).

As it turns out that the 64 pin version of this MCU does not have a VREF pin, and VDDA is actually the supply for the ADC itself, I'm unsure of the consequences of how I've wired the MCU. As the ADC is powered from my 3V reference supply, will the ADC function as I wanted (i.e. the ADC using the 3V as its reference)? Or will the consequences be unexpected?

I will be correcting the mistake in the next iteration of the PCB, but it would be helpful to understand the consequences of the incorrect wiring.

Any help is greatly appreciated.

[STOne-32]

Posted on July 31, 2017 at 15:35

Dear

oliver_2017

‌,

It is out of our specs ( See extract from Datasheets, Table 10 is AMR Absolute Maximum rating, that means if exceeded a damage may happen) . But we tolerate 300mV only during power-up when VDD and VDDA are Ramping. So no guarantee from ST and PCB rework is required.

Cheers,

STOne-