STM32L151X8 datasheet(25/133 Pages) STMICROELECTRONICS

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STM32L151x6/8/B STM32L152x6/8/B

Functional overview

3.10

ADC (analog-to-digital converter)

A 12-bit analog-to-digital converters is embedded into STM32L151x6/8/B and

STM32L152x6/8/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 VSENSE 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 Table 58:

Temperature sensor calibration values.

3.10.2

Internal voltage reference (VREFINT)

The internal voltage reference (VREFINT) provides a stable (bandgap) voltage output for the

ADC and Comparators. VREFINT is internally connected to the ADC_IN17 input channel. It

enables accurate monitoring of the VDD value (when no external voltage, VREF+, is

available for ADC). The precise voltage of VREFINT 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.

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