Datasheet

Functional overview STM32F051x
18/105 Doc ID 022265 Rev 3
3.10.3 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.
3.11 Digital-to-analog converter (DAC)
The 12-bit buffered DAC channel can be used to convert digital signals into analog voltage
signal outputs. The chosen design structure is composed of integrated resistor strings and
an amplifier in non-inverting configuration.
This digital Interface supports the following features:
● Left or right data alignment in 12-bit mode
● Synchronized update capability
● DMA capability
● External triggers for conversion
Five DAC trigger inputs are used in the device. The DAC is triggered through the timer
trigger outputs and the DAC interface is generating it’s own DMA requests.
3.12 Comparators (COMP)
The device embeds two fast rail-to-rail low-power comparators with programmable reference
voltage (internal or external), hysteresis and speed (low speed for low power) and with
selectable output polarity.
The reference voltage can be one of the following:
● External I/O
● DAC output pin
● Internal reference voltage or submultiple (1/4, 1/2, 3/4). Refer to Table 24: Embedded
internal reference voltage for the value and precision of the internal reference voltage.
Both comparators can wake up from STOP mode, generate interrupts and breaks for the
timers and can be also combined into a window comparator.
The internal voltage reference is also connected to ADC_IN17 input channel of the ADC.
3.13 Touch sensing controller (TSC)
The STM32F051x devices provide a simple solution for adding capacitive sensing
functionality to any application. Capacitive sensing technology is able to detect the presence
of a finger near an electrode which is protected from direct touch by a dielectric (glass,
plastic, ...). The capacitive variation introduced by the finger (or any conductive object) is
measured using a proven implementation based on a surface charge transfer acquisition
principle. It consists of charging the electrode capacitance and then transferring a part of the
accumulated charges into a sampling capacitor until the voltage across this capacitor has
reached a specific threshold. To limit the CPU bandwidth usage this acquisition is directly
managed by the hardware touch sensing controller and only requires few external