Stm32l4 Series MCU ADC accurately calculates input voltage through internal reference voltage

With STM32L476 For example ,VREFINT And inside ADC1_INP0 Connected to a

When VDDA And VREF+ When the pins are connected together , The voltage may fluctuate , This will lead to ADC The conversion error is very large , Therefore, the actual reference voltage at this time can be calculated by using the internal reference voltage of the single chip microcomputer VREF+.

VREFINT_CAL: From the address in the figure below 0x1FFF 75AA-0x1FFF75AB read out ;

VREF+_Charac:3.0V(±10mV);

VREFINT_DATA:ADC1_INP0 The result of the current conversion ADC The number .

For a ADC In terms of channels , The voltage value collected by this channel is consistent with the reference voltage VREF+ There is a proportional relationship between , As follows :

When VDDA When unknown （VDDA And VREF+ Connected to a ）, There may be fluctuations , In order to make the expression of the collected actual voltage value of the channel and VDDA irrelevant , in other words VDDA（ or VREF+） use (1) Formula substitution , So you can get （3） type ：

FULL_SCALE:4095;

VREF+_Charac:3.0V(±10mV);

VREFINT_CAL: From the address in the figure below 0x1FFF 75AA-0x1FFF75AB read out ;

VREFINT_DATA:ADC1_INP0 The result of the current conversion ADC The number .

ADC_DATA： V_CHANNELx The corresponding ADC The converted digital value ;

VREFINT_CAL Value reading method :wVREFINT_CAL = *(__IO uint16_t *)(0x1FFF75AA);