STM32L031X4 datasheet(27/126 Pages) STMICROELECTRONICS

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DS10668 Rev 6

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STM32L031x4/6

Functional overview

3.11

Analog-to-digital converter (ADC)

A native 12-bit, extended to 16-bit through hardware oversampling, analog-to-digital

converter is embedded into STM32L031x4/6 devices. It has up to 10 external channels and

3 internal channels (temperature sensor, voltage reference). Three channel are fast

channel, PA0, PA4 and PA5, while the others are standard channels.

It performs conversions in single-shot or scan mode. In scan mode, automatic conversion is

performed on a selected group of analog inputs.

The ADC frequency is independent from the CPU frequency, allowing maximum sampling

rate of 1.14 Msps even with a low CPU speed. The ADC consumption is low at all

frequencies (~25 µA at 10 kSPS, ~200 µA at 1 Msps). An auto-shutdown function

guarantees that the ADC is powered off except during the active conversion phase.

The ADC can be served by the DMA controller. It can operate from a supply voltage down to

1.65 V.

The ADC features a hardware oversampler up to 256 samples, this improves the resolution

to 16 bits (see AN2668).

An analog watchdog feature allows very precise monitoring of the converted voltage of one,

some or all scanned 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 triggers, to allow the application to synchronize A/D conversions and timers.

3.12

Temperature sensor

The temperature sensor (TSENSE) generates a voltage VSENSE that varies linearly with

temperature.

The temperature sensor is internally connected to the ADC_IN18 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.

Table 7. Temperature sensor calibration values

Calibration value name

Description

Memory address

TSENSE_CAL1

TS ADC raw data acquired at

temperature of 30 °C, VDDA= 3 V

0x1FF8 007A - 0x1FF8 007B

TSENSE_CAL2

TS ADC raw data acquired at

temperature of 130 °C, VDDA= 3 V

0x1FF8 007E - 0x1FF8 007F

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