Datasheet

Functional overview STM32L475xx
42/204 DS10969 Rev 5
The main features of the touch sensing controller are the following:
• Proven and robust surface charge transfer acquisition principle
• Supports up to 21 capacitive sensing channels
• Up to 3 capacitive sensing channels can be acquired in parallel offering a very good
response time
• Spread spectrum feature to improve system robustness in noisy environments
• Full hardware management of the charge transfer acquisition sequence
• Programmable charge transfer frequency
• Programmable sampling capacitor I/O pin
• Programmable channel I/O pin
• Programmable max count value to avoid long acquisition when a channel is faulty
• Dedicated end of acquisition and max count error flags with interrupt capability
• One sampling capacitor for up to 3 capacitive sensing channels to reduce the system
components
• Compatible with proximity, touchkey, linear and rotary touch sensor implementation
• Designed to operate with STMTouch touch sensing firmware library
Note: The number of capacitive sensing channels is dependent on the size of the packages and
subject to I/O availability.
3.21 Digital filter for Sigma-Delta Modulators (DFSDM)
The device embeds one DFSDM with 4 digital filters modules and 8 external input serial
channels (transceivers) or alternately 8 internal parallel inputs support.
The DFSDM peripheral is dedicated to interface the external  modulators to
microcontroller and then to perform digital filtering of the received data streams (which
represent analog value on  modulators inputs). DFSDM can also interface PDM (Pulse
Density Modulation) microphones and perform PDM to PCM conversion and filtering in
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