5 Replies Latest reply on Mar 10, 2019 10:16 PM by YuMa_1534086

    Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.

    YuMa_1534086

      Our customer evaluates PSoC4S(CY8C4045AZI).

       

      In system tab of PSoC Creator, there is a cell to input VDD voltage.(below figure)

       

       

      They found that rawcount changes by this VDD setting even if actual VDD voltage is same.

       

      They checked at below 2 case.

      Case 1:                VDD setting of system tab: 3.3V,    Actual VDD voltage: 1.8V

      Case 2:                VDD setting of system tab: 1.8V,    Actual VDD voltage: 1.8V

       

      rawcount of Case1 and 2 is different even if actual VDD is same 1.8V.

       

      Below is customer’s questions.

      Please confirm and answer below questions.

       

      Q1)

      Should VDD setting(system tab) be set according to actual VDD?

      If yes, what kind of influence or problem will occur when VDD setting(system tab) different from actual VDD?

       

      Q2)

      Why does rawcount change by VDD setting(system tab)?

      What impact does VDD setting(system tab) have on capsense function and block?

       

       

      Best Regards.

       

        • 1. Re: Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.
          YuMa_1534086

          Hello

           

           

          Q1)

          I found below link.

          => https://community.cypress.com/docs/DOC-13706

           

          PSoC4S capsense vref is determined not by actual VDD voltage but by cydwr VDD setting.

          So Rawcount is changed by cydwr VDD setting.

          Is my understanding correct?

           

           

          Q2)

          Could you please let us know how to set cydwr VDD setting?

          Should cydwr VDD setting be the same value as actual VDD voltage?

          Or can user freely set cydwr VDD setting if it is lower than actual VDD voltage?

          (For example, actual VDD is 5V. User can set cydwr VDD in the range of 1.8V to 4.9V.)

           

          And what kind of influence or problem will occur when VDD setting(system tab) different from actual VDD?

           

           

          Best Regards.

          Matsubara

          • 2. Re: Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.
            RuzheZ_36

            Matsubara-san,

             

            Added some comments about your questions.

             

            Q1)

            PSoC4S capsense vref is determined not by actual VDD voltage but by cydwr VDD setting.

            So Rawcount is changed by cydwr VDD setting.

            A1)

            You understanding is correct.

             

            Q2)

            Could you please let us know how to set cydwr VDD setting?

            Should cydwr VDD setting be the same value as actual VDD voltage?

            Or can user freely set cydwr VDD setting if it is lower than actual VDD voltage?

            (For example, actual VDD is 5V. User can set cydwr VDD in the range of 1.8V to 4.9V.)

            And what kind of influence or problem will occur when VDD setting(system tab) different from actual VDD?

             

            A2)

            Users can set cydwr VDD freely if cydwr VDD setting is lower than actual VDD voltage. However, we suggest using same cydwr VDD with actual VDD. Because higher cydwr VDD settings tend to generating higher Vref. Higher Vref will help to increase CapSense SNR in most cases.

            If VDD setting(system tab) doesn't match actual VDD, it may not get fine tuning result of CapSense. For example, If actual VDD is 5V, VDD setting is 1.8V(means Vref is 1.2V), the signal will be lower than VDD settings = 5V. Another worse influence is that, it may lead to Auto-Calibration failed. For example, If actual VDD is 1.8V, VDD settings is 5V(means the chip should provide a 2.7429V Vref), but actually the chip can not boost to a voltage higher than its actual VDD voltage. That may lead to CapSense stuck.  

             

            Thanks,

            Ryan

            • 3. Re: Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.
              YuMa_1534086

              Ryan-san.

               

              Thank you for your support.

               

              You answered that user can not set a higher value to cydwr VDD than actual VDD.

               

              Is it possible to set a value lower than actual VDD to cydwr VDD?

              For example, actual VDD is 5V and cydwr 3.3V.

               

              If it is OK, I thinks that cydwr VDD could be used for sensitivity adjustment.

              For example, it is case that sensitivity is too high.

              If raw count with touch saturates due to high sensitivity and this saturation can not be solved by other parameter, I thought that cydwr VDD could be used.

               

              Is it possible to set a value lower than actual VDD to cydwr VDD to tune sensitivity?

              (This is case that user needs not high SNR)

              Or is there a possibility that auto-calibration will fail even if cydwr VDD is lower than actual VDD?

               

               

              Best Regards.

              Matsubara

              • 4. Re: Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.
                RuzheZ_36

                Hello Matsubara-san

                 

                Yes. You're rigth. Cydwr VDD could be used for sensitivity adjustment.

                Yes. It is possible to set a value lower than actual VDD to cydwr VDD to tune sensitivity.

                Generally, auto-calibration will not fail if cydwr VDD is lower than actual VDD. In some extreme cases, for example, if noise on GND is too large. Low Vref (Lower VDD settings) may have more risk(not necessarily) to cause auto-calibration failed.

                 

                Thanks,

                Ryan

                • 5. Re: Regarding PSoC4S(CY8C4045AZI) Rawcount by VDD setting of PSoC creator system tab.
                  YuMa_1534086

                  Ryan-san.

                   

                  Thank you for your support.

                  I understand.

                   

                  Best Regards.

                  Matsubara