3.5 SHIELD – Driven Shield

The MTCH2120 features a Driven shield and Driven shield+ options to enhance touch sensitivity and enable a water-tolerant touch. A driven shield signal can be provided on a dedicated pin and/or on all not-scanned buttons (called Driven Shield+). Driven Shield+ functionality is very effective in multi-button designs, shielding trace lines, etc. The shielding signal is provided on pin BUTTON11 when the dedicated shield is enabled.

Driven Shield benefits:
  • Reducing capacitive sensor load (e.g., enabling to the reduction of CSD, scan time, and power consumption in consequence)
  • Establishing water tolerance. Recommend using Driven Shield+ so that the buttons not currently measured are driven as a shield, helping to avoid false detection due to the water bridge between the multiple buttons.
  • If used as an alternative to a passive ground shield, unlike a ground shield, a driven shield will neither reduce sensitivity nor increase sensor capacitance

Refer to the Microchip Capacitive Touch Design Guide – AN2934 for further details and layout considerations for Driven Shield and Driven Shield Plus usage.

Steps to Configure Driven Shield

  • Disable Button 11 by writing 0 to the Sensor Enable (EN) bit in the Sensor Control (SENCTRL) register

    Note: The Driven Shield is integrated with the Button 11 pin. Therefore Button 11 must be disabled.

  • Enable the Driven Shield by writing 1 to the Driven Shield (DS) bit in the Device Control (DEVCTRL) register

Steps to Configure Driven Shield Plus

  • The Enable Driven Shield Plus by writing 1 to the Driven Shield Plus (DSP) bit in the Device Control (DEVCTRL) register

Note:

Enabling or disabling the Shield feature by the Host requires a restart after the configuration update. Refer to theConfiguration Summary for more details.