Datasheet

Functional overview STM32L431xx
36/200 DocID028800 Rev 1
3.19 Operational amplifier (OPAMP)
The STM32L431xx embeds one operational amplifier with external or internal follower
routing and PGA capability.
The operational amplifier features:
• Low input bias current
• Low offset voltage
• Low-power mode
• Rail-to-rail input
3.20 Touch sensing controller (TSC)
The touch sensing controller provides a simple solution for adding capacitive sensing
functionality to any application. Capacitive sensing technology is able to detect finger
presence near an electrode 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.
The touch sensing controller is fully supported by the STMTouch touch sensing firmware
library which is free to use and allows touch sensing functionality to be implemented reliably
in the end application.
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 Random number generator (RNG)
All devices embed an RNG that delivers 32-bit random numbers generated by an integrated
analog circuit.
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