Actual IDAC Current Value of PSoC 4 CapSense - KBA229074

Version 2

    Author: RyanZ_36          Version: **

     

    The actual IDAC current value (in µA) of PSoC® 4 CapSense® can be calculated with the following equation:

    IDAC_Current_Value = IDAC_Gain × IDAC

    Where IDAC_Gain is the least significant bit of the IDAC current value (in nA or µA), and IDAC is a Modulator IDAC or Compensation IDAC (if compensation IDAC is enabled) value set in firmware.

    When IDAC auto-calibration is disabled, you can set appropriate values for these two IDAC parameters in the CapSense Component Configuration GUI. When IDAC auto-calibration is enabled, CapSense will calibrate suitable values for these two IDAC automatically. 

     

    IDAC_Gain can be set as 1.2 µA/bit (default) or 2.4 µA/bit for CSDv1; and 2.4 µA/bit, 300 nA/bit, or 37.5 nA/bit for CSDv2.

    Here is an example. Assume IDAC_Gain is 2.4 µA/bit, Modulator IDAC is 11, and Compensation IDAC is 9. Ideally, the actual IDAC current values are:

    • Actual Modulator IDAC current value = 2.4 µA/bit ×= 26.4 µA;
    • Actual CompensationµA/bit × 9 = 21.6 µA.

    Note that PSoC 4 IDAC has a ±10% error for full scale. You should consider this error in your actual applications.

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    Reference Document:
    PSoC 4 Capacitive Sensing (CapSense®)
    AN85951 - PSoC® 4 and PSoC® 6 MCU CapSense® Design Guide
    32-bit Arm® Cortex®-M0 PSoC® 4