STM32F051K4 datasheet(18/104 Pages) STMICROELECTRONICS

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Functional overview

STM32F051x

18/105

Doc ID 022265 Rev 3

3.10.3

VBAT battery voltage monitoring

This embedded hardware feature allows the application to measure the VBAT battery voltage

using the internal ADC channel ADC_IN18. As the VBAT voltage may be higher than VDDA,

and thus outside the ADC input range, the VBAT pin is internally connected to a bridge

divider by 2. As a consequence, the converted digital value is half the VBAT 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

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