STM32 ADC power supply

[LSind.1]

Customer asks me to use STM32 powered from 3.3V with ADC reference 3.3V too (different source). So there is two possibel topologies:

1. Connect VDD and VDDA, use precision source for VREF
2. Connect VDDA and VREF to precision source, VDD connect to standard source.

In the DS I didnt found clear info about this:

"A maximum difference of 300 mV between VDD and VDDA can be tolerated during power-up and power-down operation"

"VDDA Must be the same potential as VDD"

"The voltage on VREF+ may range between 2.4 V and VDDA"

In my case, standard 3.3V source can differ +/-200mV from reference 3.3V source. Is it acceptable to use STM32F405 this way?

[Bowman32]

Hello @LSind.1​ 

Connect VDD and VDDA, use precision source for VREF but make sure that VREF < = VDDA

For more details about ADC characteristics refer to table 67 in the STM32F405 datasheet DocID022152 Rev 8

Best regards

Bouraoui