4 Replies Latest reply on Jan 9, 2020 9:05 PM by masu_1341616

    MBR3 Proximity Guideline

    masu_1341616

      I can see on your reccomendation of "General layout guideline of CY8CMBR3xxx_Design_Toolbox.xlsx" .

       

       

      Our Proximity Spec

      - Proximity Loop diameter      19mm

      - Required Proximity Distance  19mm

       

       

      Guideline

      Proximity sensor Parasitic Capacitance (Cp)

      Min 8 pF -- Max 45 pF

       

       

      I input our parameter to "Table B: Cp Calclator of CY8CMBR3xxx_Design_Toolbox.xlsx".

      This resuilt 6pFis out of your recommendation.  6pF < min 8pF

       

       

      If you have any concern about this result. Please advice to avoid issue.

        • 1. Re: MBR3 Proximity Guideline
          AH_96

          Hi masu_1341616

           

          Since MBR3 device uses smartsense algorithm for tuning, it is recommended to ensure that Cp criteria is met.

          In the layout, you can leave a jumper to add a parallel capacitor in the proximity sensor trace if needed. This will ensure that Cp (parasitic capacitance) is added to the pin as observed by the MBR3 device and allows setting the parameters accordingly. In a prototype of the layout, if the sensor is not working as expected due to small Cp, the parallel cap will help adjust the capacitance.

           

          Best regards

          Hari

          • 2. Re: MBR3 Proximity Guideline
            masu_1341616

            Hello Hari,

             

            Thank you for your help.

            I have aquestion about the parallel cap.

            Does it have to connect to loop sensor and GND?

            Do you have any advice about pattern layout? I will layout this pattern near by MBR3 IO.

             

            Best Regards,

            Masa

            • 3. Re: MBR3 Proximity Guideline
              AH_96

              Hi Masa-san,

               

              Yes, the Capacitor needs to be connected to the loop sensor and ground. This need not be connected always and is required only if you observe poor sensor performance.

              The parallel capacitor needs to be placed after the 560 ohm series resistor.

               

              For the proximity sensor, the general guidelines need to be followed. A 1.5 mm thick sensor trace forming a loop will act as a proximity sensor. Providing a ground loop around the proximity sensor will help in improving noise performance.

               

              You can also refer MBR3 CapSense design guide for more details.

               

              Best regards

              Hari

              • 4. Re: MBR3 Proximity Guideline
                masu_1341616

                Hello Hari-san,

                 

                Thank you for your answer. I update the design.

                 

                Best regards,

                Masa