Datasheet

DocID17659 Rev 9 25/131

STM32L151x6/8/B, STM32L152x6/8/B Functional overview

This dual digital Interface supports the following features:

• two DAC converters: one for each output channel

• left or right data alignment in 12-bit mode

• synchronized update capability

• noise-wave generation

• triangular-wave generation

• dual DAC channels’ independent or simultaneous conversions

• DMA capability for each channel (including the underrun interrupt)

• external triggers for conversion

• input reference voltage V

REF+

Eight DAC trigger inputs are used in the STM32L15xxx. The DAC channels are triggered

through the timer update outputs that are also connected to different DMA channels.

3.12 Ultralow power comparators and reference voltage

The STM32L15xxx embeds two comparators sharing the same current bias and reference

voltage. The reference voltage can be internal or external (coming from an I/O).

• one comparator with fixed threshold

• one comparator with rail-to-rail inputs, fast or slow mode. The threshold can be one of

the following:

– DAC output

– External I/O

– Internal reference voltage (V

REFINT

) or V

REFINT

submultiple (1/4, 1/2, 3/4)

Both comparators can wake up from Stop mode, and be combined into a window

comparator.

The internal reference voltage is available externally via a low power / low current output

buffer (driving current capability of 1 µA typical).

3.13 Routing interface

This interface controls the internal routing of I/Os to TIM2, TIM3, TIM4 and to the

comparator and reference voltage output.

3.14 Touch sensing

The STM32L15xxx devices provide a simple solution for adding capacitive sensing

functionality to any application. These devices offer up to 20 capacitive sensing channels

distributed over 10 analog I/O groups. Only software capacitive sensing acquisition mode is

supported.

Capacitive sensing technology is able to detect the presence of a finger near a sensor which

is protected from direct touch by a dielectric (glass, plastic, ...). The capacitive variation

introduced by the finger (or any conductive object) is measured using a proven

implementation based on a surface charge transfer acquisition principle. It consists of

charging the sensor capacitance and then transferring a part of the accumulated charges