3.7.1 Operation

Low-Power Feature Disabled

When the low-power feature is disabled, MTCH2120 stays in Active mode, where all the enabled buttons are scanned at intervals defined by Touch Measurement Period MP.

Low-Power Feature Enabled

When the low-power feature is enabled, and no buttons are touched for the Time-Out Configuration (Refer to the Time-Out Config (TIMEOUTCONF) register) period, MTCH2120 will enter the low-power mode. In low-power mode, buttons with the Low-Power Sensor [LP] bit set to 0 in the Sensor Control (SENCTRL) register are suspended from scanning. In low-power mode, only the buttons with the Low-Power Sensor [LP] bit set to 1 in the Sensor Control (SENCTRL) register are enabled for scanning. These low-power buttons are scanned at the measurement period defined by low-power measurement period (Refer to the Low-Power Measurement Period (LPMP) register). The suspended buttons are resumed and calibrated when a touch is detected on low-power buttons. The system returns to active mode.

Note: The Low-Power mode must be disabled by the Host within the period configured in the Time-Out Config (TIMEOUTCONF) register so MTCH2120 stays in the active mode. If the Host doesn't disable the Low Power mode, the device will reenter low-power mode automatically after a Time-Out period of no touch is detected.

While in Low-Power mode, the Host may switch to regular operation (active mode) at any time with immediate effect. The Low-Power mode can be used as a power button to unlock other keys or as a proximity trigger to detect an approaching finger towards the panel to activate the touch-sensor panel. The figure shows the operation sequence taking place between active and Low-Power mode when Low-Power mode is enabled.

Power consumption depends on the number of low-power buttons enabled and the low-power measurement period. The exemplary use case is the power buttons on a device: Only the power buttons will turn on the device. After the device is turned on, all the buttons must be active and scanned.

Note: Then the host sends any I2C command to the device, it will exit the low-power mode.
Note: Auto Threshold and Frequency Hopping with Auto-Tune features are disabled when the device enters the low-power mode.