3 Replies Latest reply on Jan 13, 2020 1:08 AM by AH_96

    Spread spectrum modulation rate of Fourth-generation CapSense

    NaMo_1534561

      Hello,

       

      What is the modulation rate(%) or modulation frequency of spread spectrum of Fourth-generation CapSense in each setting of SSC6, SSC7, SSC9 and SSC10?

      Also, is the modulation rate the center spread or down spread?

       

      Best Regards,

      Naoaki Morimoto

        • 1. Re: Spread spectrum modulation rate of Fourth-generation CapSense
          AH_96

          Hello NaMo_1534561

           

          SSC does not "modulate" the sense clock. It only spreads the clock frequency based on an LFSR. The spread spectrum frequency range must be within +/-10% of the sense clock frequency. This is taken care by the component and the component will allow you to choose the value only if this condition is satisfied. Please refer the component datasheet for details on the conditions required to be satisfied while choosing SSC.

           

          Spread spectrum is center spread with center frequency equal to the sense clock frequency set in the component.

           

          Best regards

          Hari

          • 2. Re: Spread spectrum modulation rate of Fourth-generation CapSense
            NaMo_1534561

            Hello Hari-san,

             

            In the CSD (Self-cap) setting, the switching signal period on the sensor measured under the following conditions was 21.12us to 21.24us.

            SSC7

            Resolution 14bit

            Modulation Clk 24000KHz

            SnsClk 46.88KHz

             

            It looks like it is the same as the Direct waveform.

            Are there any other settings required to enable SSC?

             

            Best regards,

            Naoaki Morimoto

            • 3. Re: Spread spectrum modulation rate of Fourth-generation CapSense
              AH_96

              Hi NaMo_1534561

               

              There are two conditions that need to be satisfied for SSC to take effect.

              1.

               

              2.

               

              In the present configuration, condition 2 is not getting satisfied, as resolution, N = 14, mod clock = 24000kHz, SSCN = 7 and snsclk = 46.88.

               

              Please make sure that the configuration satisfies the condition so that the component sets SSC correctly. If this condition is not satisfied, the component switches to Direct by default.

               

              Best regards

              Harigovind