This application note provides a guide to the selection of the right sampling capacitor (CS) for applications based on STM8T141 and touch sensing library-based capacitive sensors.
This application note helps designers select the appropriate sampling capacitor (Cs) for STM8T141 devices and touch sensing library-based capacitive sensors. It investigates non-ideal capacitor characteristics, such as dielectric absorption, temperature coefficients, and dissipation factors, which can limit performance in specific applications.
The document details the charge transfer acquisition principle used by these sensors and explains how environmental changes affect operation. It provides a comparison of various capacitor dielectrics (PET, PEN, PPS, NPO, X7R, Tantalum) based on operating temperature, dissipation factor, and reliability. Specific recommendations are given for low power modes, proximity detection, and touch detection scenarios.
| Target Device | STM8T141 |
|---|---|
| Document ID | 15600 |
| Publication Date | November 2011 |
PET, PEN, PPS, or NPO capacitor types must be used.
No, all capacitor types except tantalum can be used for touch detection.
Their high dissipation factor and capacitance change over temperature make their performance unacceptable.