29.2 Embedded Characteristics

  • Implements Low-power, High-sensitivity, Environmentally-robust Capacitive Touch Buttons, Sliders, and Wheels
    • One Pin per Electrode – No External Components
    • Zero Drift over Temperature and supply/reference ranges
    • No Need for Temperature or supply/reference compensation
  • “On demand” or “Timed” measurement
  • Supports Mutual Capacitance and Self-capacitance Sensing
    • Up to 8 Buttons in Self-capacitance Mode
    • Up to 64 Buttons in Mutual Capacitance Mode
    • Supports Lumped Mode Configuration(1)
  • Calibration
    • Load Compensating Charge Sensing
    • Parasitic capacitance compensation together with the electrode capacitance
  • Adjustable Gain for Higher Sensitivity
    • Analog Gain 1 to 16
    • Digital Gain 1 to 32
  • Noise Immunity
    • Hardware Noise Filtering by Accumulation 1 to 64
    • Adjacent Key Suppression (AKS), Removal of False Detection(2)
    • Frequency Hopping: Noise Signal Desynchronization for High Conducted Immunity(3)
  • Provided PTC Subsystem Firmware(4)
  • Acquisition Module (Node Definitions, pPP and PTC Management) is Product-dependent, which implements all Hardware-dependent Operations for Configuration and Measurement of Capacitive Touch or Proximity Sensors
  • Signal Conditioning Module (Frequency Hopping) applies Algorithmic and Feedback Control Methods to improve the Quality of Measurement Data captured by an Acquisition Module
  • Post-processing Modules (Key, Scroller) interpret Measurement Data in the Context of a Capacitive Touch or Proximity Sensor
  • Scroller Module defines Slider and Wheels Configuration and Data, based on Keys Module Setting
Note:
  1. A lumped sensor is implemented as a combination of multiple sense lines (self-capacitance measurement) or multiple drive and sense lines (mutual capacitance measurement) to act as one single button sensor. This provides the application developer with greater flexibility in the touch sensor implementation.
  2. The PTC incorporates the Adjacent Key Suppression (AKS) technology, which can be selected on a per-key basis. The AKS technology is used to suppress multiple key presses based on relative signal strength. This feature assists in solving the problem of surface moisture which can bridge a key touch to an adjacent key, causing multiple key presses.
  3. This PTC subsystem supports frequency hopping, which tries to select a sampling frequency that does not clash with noise at specific frequencies elsewhere in products or product operating environments. Frequency Hopping tries to hop away from the noise.
  4. It is necessary to use the firmware provided by Microchip in order to use the PTC subsystem.