Datasheet

Functional overview STM32L011x3/4
26/119 DocID027973 Rev 5
3.10 Analog-to-digital converter (ADC)
A native 12-bit, extended to 16-bit through hardware oversampling, analog-to-digital
converter is embedded into STM32L011x3/4 devices. It has up to 10 external channels and
2 internal channels (temperature sensor, voltage reference). Three channels, PA0, PA4 and
PA5, are fast channels, while the others are standard channels.
The ADC 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 1MSPS). 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.
3.11 Temperature sensor
The temperature sensor (T
SENSE
) generates a voltage V
SENSE
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 (see Table 57:
Temperature sensor calibration values).
3.11.1 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 (since no external voltage, V
REF+
, 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 (see Table 20: Embedded internal
reference voltage calibration values). It is accessible in read-only mode.
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