3 Replies Latest reply on Jun 6, 2011 3:15 PM by content.librarian

    Programmable Clock Generator CY22150

    piotr.seliukou

      Data obtained from CyberClocks for CY22150 for Charge Pump Settings [40H (2 .. 0)] does not coincide with the requirements of Table 9 from the file Document #: 38-07104 Rev. * K.
       

        • 1. Re: Programmable Clock Generator CY22150
          content.librarian

          The CyClocksRT uses a proprietary algorithm to optimize the charge pump value. The table in the datasheet will give you guaranteed PLL stability, but will not necessarily be the optimum solution. We recommend referencing the CyClocksRT charge pump value for critical configurations.

          The datasheet values are set to cover a wide range of possible P values, while CyClocksRT knows exactly which P value you will be using.

          The datasheet table chooses the lowest charge pump value acceptable for a specific range of P values; the lowest value will give you the most stability margin.

          CyClocksRT goes from the highest charge pump setting and calculates the loop bandwidth, if the phase detector frequency, which is equal to VCO/P, is 5 times greater than the calculated bandwidth it will stop searching. Otherwise it will go to the next lower charge pump setting and go through the calculation again.

          This is why you see values from software different from the table in the datasheet. 

          The charge pump values that you get from the table in the datasheet are valid entries, and will give you a stable clock output.

          The values generated out of both CyClocksRT and table 9 will guarantee stability. There is a range in which the charge pump can be set and the values from table 9 are usually around the center of that stability region. CyClocksRT will try to get to the optimum area of the stability region.

          • 2. Re: Programmable Clock Generator CY22150
            piotr.seliukou
                 Thank you for your reply. I compared several options for data from CyClocksRT for CY22150
            for the frequency input from 1MHz to 10MHz and an output frequency equal to 8 * Finput and received for the charge pump setting the same value = [100]. Therefore, I have a question.
            Now I understand.
               
            • 3. Re: Programmable Clock Generator CY22150
              content.librarian

              We recommend using the CyClocksRT as the software uses a proprietary algorithm to calculate the PLL stability and will give the most optimal configuration possible. The datasheet values are there for broad general use and is not optimized for specific configurations.     

               

                 

                   

                          

                 

              The datasheet table chooses the lowest charge pump value acceptable for a specific range of P values, the lowest value will give you the most stability margin not stability.