ST STM32G471 User Manual

Analog-to-digital converters (ADC) RM0440
684/2126 RM0440 Rev 4
21.4.33 Monitoring the internal voltage reference
It is possible to monitor the internal voltage reference (V
REFINT
) to have a reference point for
evaluating the ADC V
REF+
voltage level.
The internal reference voltage (V
REFINT
) is internally connected to ADC1_INP18,
ADC3_INP18, ADC4_INP18 and ADC5_INP18.
Refer to the electrical characteristics section of the product datasheet for the sampling time
value to be applied when converting the internal voltage reference voltage.
Figure 155 shows the block diagram of the V
REFINT
sensing feature.
Figure 155. V
REFINT
channel block diagram
1. The VREFEN bit into ADCx_CCR register must be set to enable the conversion of internal channels
(V
REFINT
).
Calculating the actual V
DDA
voltage using the internal reference voltage
The power supply voltage applied to the device may be subject to variations or not precisely
known. When V
DDA
is connected to V
REF+
, it is possible to compute the actual V
DDA
voltage
using the embedded internal reference voltage (V
REFINT
). V
REFINT
and its calibration data
acquired by the ADC during the manufacturing process at V
DDA_Charac
can be used to
evaluate the actual V
DDA
voltage level.
The following formula gives the actual V
DDA
voltage supplying the device:
Where:
• VREFINT_CAL is the V
REFINT
calibration value
• VREFINT_DATA is the actual V
REFINT
output value converted by ADC
Converting a supply-relative ADC measurement to an absolute voltage value
The ADC is designed to deliver a digital value corresponding to the ratio between V
REF+
and
the voltage applied on the converted channel.
For most applications V
DDA
value is unknown and ADC converted values are right-aligned.
In this case, it is necessary to convert this ratio into a voltage independent from V
DDA
:
MSv34467V5
V
REFINT
ADCx
ADC input
VREFEN control bit
Internal
power block
V
REF+
V
DDA_Charac
VREFINT_CAL VREFINT_DATA⁄×=
V
CHANNELx
V
REF+
FULL_SCALE
-------------------------------------
ADC_DATA×=

ST STM32G471 Specifications

General

Brand	ST
Model	STM32G471
Category	Microcontrollers
Language	English