3 Replies Latest reply on Sep 26, 2018 1:10 AM by ring

    CAP sensing raw data drifting problem (CY8CMR3102)

    user_36905748

      Hi,

       

      I started a new design with CY8CMR3102, used a STM32F103 MCU to configure and read the raw data from Sensor by I2C.

       

      The PCB is a round shape(6cm diameter), a 1mm wide trace on edge of board as Proxmitiy sensor's antenna ( connects to CS0 pin though a 560ohm resistors).

      CMOD is 2.2nF.

       

      Here is the problem: the raw data I retrieved from sensor drifting a lot. In amibent temperature, the board will take 1 mintues to stay on the stable reading level. Then I put the board on temperature chamber running from -20(C) degree to +70(C)degree, monitoring the raw data, it will drift singanificant amount. I did try different configuration by setting different sensitivity value, different filters, enable/disable EMC function, but none of them can stop the raw data drifting.

       

      My first guess is the whole pcb 's capacitance would impact the CMOD pin?  Or some charging/discharing problem between the proximity sensor antenna and the ground plane?

       

      Any suggestions/thoughts will be greatly appreciated!