Note: Firmware package H7 V1.10.0
On the STM32H723 the internal vref and temp channels are connected to ADC3 which is a 12b ADC while ADC1 and 2 are 16b.
The internal calibration values for the temperature sensor and vref are also scaled in 12b it seems but the HAL
Macros __HAL_ADC_CALC_VREFANALOG_VOLTAGE (in stm32h7xx_hal_adc.h) or __LL_ADC_CALC_DATA_TO_VOLTAGE (in stm32h7xx_ll_adc.h) assume a scaling in 16b resulting in incorrect readings if the actual adc resolution of 12b is passed to these macros instead of 16b.
Passing a resolution of 16b and the actually 12b value from ADC3 to these functions results in a correct value.
The same also applies to the macro __LL_ADC_CALC_TEMPERATURE and possibly others.
The comment to __LL_ADC_CALC_DATA_TO_VOLTAGE states:
"On this STM32 series, calibration data of internal voltage reference
* VrefInt corresponds to a resolution of 16 bits" which is incorrect for this chip in this case.
The vref calibration value on one specific chip here is 0x5F1 = 1521 which is as expected close to what the 12b adc reads on the vref channel when powered by 3.3v.
