Functional overview
STM32L151x6/8/B, STM32L152x6/8/B
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DocID17659 Rev 10
3.10
ADC (analog-to-digital converter)
A 12-bit analog-to-digital converters is embedded into STM32L15xx6/8/B devices with up to
24 external channels, performing conversions in single-shot or scan mode. 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.
The events generated by the general-purpose timers (TIMx) can be internally connected to
the ADC start trigger and injection trigger, to allow the application to synchronize A/D
conversions and timers. An injection mode allows high priority conversions to be done by
interrupting a scan mode which runs in as a background task.
The ADC includes a specific low power mode. The converter is able to operate at maximum
speed even if the CPU is operating at a very low frequency and has an auto-shutdown
function. The ADC’s runtime and analog front-end current consumption are thus minimized
whatever the MCU operating mode.
3.10.1 Temperature
sensor
The temperature sensor (TS) generates a voltage V
SENSE
that varies linearly with
temperature.
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.
The sensor provides good linearity but it has to be calibrated to obtain good overall
accuracy of the temperature measurement. As the offset of the temperature sensor varies
from chip to chip due to process variation, the uncalibrated internal temperature sensor is
suitable for applications that detect temperature changes only.
To improve the accuracy of the temperature sensor measurement, each device is
individually factory-calibrated by ST. The temperature sensor factory calibration data are
stored by ST in the system memory area, accessible in read-only mode, see
Temperature sensor calibration values
3.10.2
Internal voltage reference (V
REFINT
)
The internal voltage reference (V
REFINT
) provides a stable (bandgap) voltage output for the
ADC and Comparators. V
REFINT
is internally connected to the ADC_IN17 input channel. It
enables accurate monitoring of the V
DD
value (when no external voltage, VREF+, is
available for ADC). The 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 see
Table 16: Embedded internal reference voltage
3.11
DAC (digital-to-analog converter)
The two 12-bit buffered DAC channels can be used to convert two digital signals into two
analog voltage signal outputs. The chosen design structure is composed of integrated
resistor strings and an amplifier in non-inverting configuration.
