ST STM32L4+ Series Reference Manual page 687

RM0432
21.4.34 Monitoring the internal voltage reference
It is possible to monitor the internal voltage reference (V
evaluating the ADC V
The internal voltage reference is internally connected to the input channel 0 of the ADC1
(ADC1_INP0).
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 157
1. The VREFEN bit into ADCx_CCR register must be set to enable the conversion of internal channels
(V
REFINT
Calculating the actual V
The power supply voltage applied to the device may be subject to variations or not precisely
known. When V
using the embedded internal reference voltage (V
acquired by the ADC during the manufacturing process at V
evaluate the actual V
The following formula gives the actual V
Where:
•
VREFINT_CAL is the V
•
VREFINT_DATA is the actual V
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
the voltage applied on the converted channel.
For most applications V
In this case, it is necessary to convert this ratio into a voltage independent from V
voltage level.
REF+
shows the block diagram of the V
Figure 157. V
Internal
power block
).
DDA
is connected to V
DDA
voltage level.
DDA
V V
=
REF+ DDA_Charac
REFINT
value is unknown and ADC converted values are right-aligned.
DDA
V
CHANNELx
sensing feature.
REFINT
channel block diagram
REFINT
VREFEN control bit
V
REFINT
voltage using the internal reference voltage
, it is possible to compute the actual V
REF+
REFINT
voltage supplying the device:
DDA
× VREFINT_CAL VREFINT_DATA
calibration value
output value converted by ADC
REFINT
V
REF+
------------------------------------ - ×
=
FULL_SCALE
RM0432 Rev 6
Analog-to-digital converters (ADC)
) to have a reference point for
REFINT
ADCx
ADC input
). V and its calibration data
REFINT
can be used to
DDA_Charac
⁄
ADC_DATA
MSv34467V5
voltage
DDA
and
REF+
:
DDA
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