Datasheet

STM32F051x Functional overview
Doc ID 018746 Rev 2 21/22
3.19 Analog to digital converter (ADC)
The 12-bit analog to digital converter has up to 16 external and 3 internal (temperature
sensor, voltage reference, VBAT voltage measurement) channels and performs conversions
in single-shot or scan modes. In scan mode, automatic conversion is performed on a
selected group of analog inputs.
The ADC can be served by the DMA controller.
An analog watchdog feature allows very precise monitoring of the converted voltage of one,
some or all selected channels. An interrupt is generated when the converted voltage is
outside the programmed thresholds.
3.19.1 Temperature sensor
The temperature sensor generates a voltage that varies linearly with temperature. The
conversion range is between 2 V < V
DDA
< 3.6 V. The temperature sensor is internally
connected to the ADC_IN16 input channel which is used to convert the sensor output
voltage into a digital value.
As the offset of the temperature sensor varies from chip to chip due to process variation, the
internal temperature sensor is mainly suitable for applications that detect temperature
changes instead of absolute temperatures. If an accurate temperature reading is needed,
then an external temperature sensor part should be used.
3.19.2 V
BAT
battery voltage monitoring
This embedded hardware feature allows the application to measure the V
BAT
battery voltage
using the internal ADC channel ADC_IN18. As the V
BAT
voltage may be higher than V
DDA
,
and thus outside the ADC input range, the V
BAT
pin is internally connected to a bridge
divider by 2. As a consequence, the converted digital value is half the V
BAT
voltage.
Table 9. No. of capacitive sensing channels available on STM32F051xx devices
Analog I/O group
Number of capacitive sensing channels
STM32F051Rx STM32F051Cx STM32F051Kx
G1 3 3 3
G2 3 3 3
G3 3 2 2
G4 3 3 3
G5 3 3 3
G6 3 3 0
Number of capacitive
sensing channels
18 17 14