1 Reply Latest reply on Jun 6, 2019 9:58 PM by BragadeeshV_41

    Cmod voltage wave from CY3280-BK1 board


      hello,every one.

                I captured the Cmod voltage wave from CY3280-21x34 at the CY3280-BK1 board,just as below.csd.png

      While according to 《Cypress’ CapSense Sigma-Delta Algorithm》,the wave should  like this.


      they are very different.


      how to explain the Oscilloscope wave?

        • 1. Re: Cmod voltage wave from CY3280-BK1 board

          Hi befic_2639911,


          CY8C21X34 uses first generation CSD structure( with Rbleed resistor). In this structure, Vref connected to delta-sigma comparator is adjustable based on the component config (Reference and Ref Value parameter). Hence CMOD voltage not being equal to 1.2 V is expected.


          CMOD pin will be shorted to GND to fully discharge. Hence the negative pulse, at the end of each scan cycle is also expected.