3 Replies Latest reply on Apr 14, 2019 11:45 PM by BragadeeshV_41

    Finger capacitance in smartsense

    AnDa_3584326

      Hi,

      I'm using capsense CSD v6.0 block and for better sensitivity, I made changes in finger capacitance value in smartsense(Full auto tune).

      by default value is 0.16pf, I made it 0.1pf. please tell me, change in finger capacitance value causes a misbehaving like no touch or auto sensing?

        • 1. Re: Finger capacitance in smartsense
          BragadeeshV_41

          Hi AnDa_3584326,

           

          The finger capacitance given in the configuration window is the measure of Capsense sensitivity. If you reduce the value of Cf, SmartSense increases sensitivity by increasing the scan resolution. Could you please let us know your exact observations when you decreased the Cf value?

          1. Raw counts before and after reducing Cf

          2. SNR

          3. Thickness of overlay

          4. Cp of the sensor

           

          Note: SmartSense supports a sensor parasitic capacitance range of 5 pF to 45 pF if the expected finger capacitance is higher than 0.2 pF. If the expected finger capacitance is lower than 0.2 pF, but higher than or equal to 0.1 pF, the supported parasitic capacitance range is 5 pF to 35 pF. In case you don't see any touch, this might be due to Cp greater than 35pF.

           

          Regards,

          Bragadeesh

          • 2. Re: Finger capacitance in smartsense
            AnDa_3584326

            Thank you for reply.

            But how could I measure the Cp  of the sensor when i'm using smartsense (full auto tune). 

            • 3. Re: Finger capacitance in smartsense
              BragadeeshV_41

              Hi AnDa_3584326,

               

              You have to use the Self Test library (BIST) to measure the Cp of the sensor. But you have to use either SmartSense (hardware parameters only) or Manual tuning to use this feature. SmarSense (Full Auto-Tune) and BIST (built in self test) feature can't be used together.

               

              Use any of the above two mentioned modes to measure Cp and then switch back to SmarSense (Full Auto-Tune) for normal operation.

               

              You can also use a LCR meter to measure the Cp.

               

              Regards,

              Bragadeesh