Stm32H743 ADC 16bit Really ?

[GreenGuy]

The cubemx example for ADC scan of internal channels for 743-eval shows the converted values being multiplied by 4.  So is it really 16 bit or 14?  I have verified the necessity of multiplying by 4 to get correct readings for VBat.  

[waclawek.jan]

And how is resolution (i.e. ADC_CFGR.RES) set?

JW

[SofLit]

+

AN5354 "Getting started with the STM32H7 Series MCU 16-bit ADC"

[GreenGuy]

I have read an5354 previous to posting.  It says nothing regarding choices made in the example for the stm32h743-eval example.

[GreenGuy]

In cubemx it is set to 16bit.  But your question is a good one and I will have to view the register in the debugger to see what is actually being set.

[RomainR. · Accepted solution]

Hello @GreenGuy 

There is an internal resistor divider by 4 between VBAT pin and ADC3_INP17 input channel.
Check the DS12110 Rev 10 in Table 192. VBAT monitoring characteristics the Q ratio on internal VBAT measurement.
It's also explained in RM0433 in section Table 192. VBAT monitoring characteristics.

This is why the ADC_InternalChannelConversion example compute the VBAT voltage and multiply the ADC3_INP17 by Q=4. ADC3 on STM32H74x/75x are 16bits resolution.
Hope it answers to your question.

Best regards,

Romain,