Datasheet

DocID026284 Rev 4 19/128
STM32F091xB STM32F091xC Functional overview
27
precise voltage of V
REFINT
is individually measured for each part by ST during production
test and stored in the system memory area. It is accessible in read-only mode.
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 two 12-bit buffered DAC channels 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:
• 8-bit or 12-bit monotonic output
• Left or right data alignment in 12-bit mode
• Synchronized update capability
• Noise-wave generation
• Triangular-wave generation
• Dual DAC channel independent or simultaneous conversions
• DMA capability for each channel
• External triggers for conversion
Six DAC trigger inputs are used in the device. The DAC is triggered through the timer trigger
outputs and the DAC interface is generating its 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 pins
• Internal reference voltage or submultiple (1/4, 1/2, 3/4).Refer to Table 28: Embedded
internal reference voltage for the value and precision of the internal reference voltage.
Table 4. Internal voltage reference calibration values
Calibration value name Description Memory address
VREFINT_CAL
Raw data acquired at a
temperature of 30 °C (± 5 °C),
V
DDA
= 3.3 V (± 10 mV)
0x1FFF F7BA - 0x1FFF F7BB
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