3 Replies Latest reply on Jan 1, 2020 8:52 PM by JayakrishnaT_76

    FX3 crystal frequency deviation and de

    GrWa_2302706

      Hi

       

      May I know whether the frequency deviation of crystal will affect SS signal quality ?

      If so, how does FX3 keep consistent signal quality for different frequency deviations of crystal ?

      For PCS_TX_DEEMPH bits of USB3.0 PHY Transmitter Config register, how much SS signal will change if it increases 1 ?

       

      Thanks and regards.

      Grace

        • 1. Re: FX3 crystal frequency deviation and de
          JayakrishnaT_76

          Hello,

           

          Please find my comments to your questions:

          >>May I know whether the frequency deviation of crystal will affect SS signal quality ?

          Yes, frequency deviation will affect the SS signal quality.

           

          >>If so, how does FX3 keep consistent signal quality for different frequency deviations of crystal ?

          Please refer to section 5.1.2 of the application note AN70707. It contains information regarding the maximum frequency deviation of crystal that can be used along with FX3. The link to the Application note is given below:

          https://www.cypress.com/file/139936/download

           

          >>For PCS_TX_DEEMPH bits of USB3.0 PHY Transmitter Config register, how much SS signal will change if it increases 1 ?

          When the value passed to the API CyU3PUsbSetTxDeemphasis() is increases by 1, the deemphasis level drops by 0.187dB.

           

          Best Regards,

          Jayakrishna

          • 2. Re: FX3 crystal frequency deviation and de
            GrWa_2302706

            Hi Jayakrishna

             

            If following the crystal requirements as application note, the signal quality for different boards (same PCB layout) still has large difference. How to ensure the consistency of signal quality for that case ? Thanks.

             

            BR

            Grace

            • 3. Re: FX3 crystal frequency deviation and de
              JayakrishnaT_76

              Hello,

               

              Please check whether the crystal you are using meets the requirements specified in table 4 of AN70707. If the crystal that you are using meets all the requirements specified in the Application note, then please go through the schematic and layout checklists that is mentioned in page 28 and 29 of the application note.

               

              Best Regards,

              Jayakrishna