3.3.3 CSD - Charge Share Delay

The sensors must be fully charged and discharged for each measurement to get consistent results. The RC time constant may vary based on the sensor capacitance and series resistor option. CSD must be selected optimally ensure that complete charging and discharging happen.

Operation

As seen in the section Touch Measurement Operation, touch measurement is performed by sharing charge between CC and Cx. The pulse for each sample is divided into 6-phases. Increasing CSD by one count increases the measurement time of one sample by six clock pulses. Thus, increasing the CSD will increase the charging time. Refer to the section Steps To Configure Measurement Clock Frequency and CSD for more information on tuning CSD. Using higher CSD will have an impact on Response Time.

The CSD can be configured per channel by writing the value in the CSD [n] register. Refer to the Configuration Summary sections for more information.

Steps to Configure CSD

  1. Write the value in CSD[n] register to configure the CSD.
  2. Save (Optional)
    • This save option will help to retain the values after the device is reset (or) rebooted. Otherwise, this step is optional.