3 Replies Latest reply on Dec 6, 2017 9:04 AM by weston_beal

    Ask about DDR4 Threshold crosstalk voltage setting!

    hmbui@apm.com

      Hi Expert,

       

      I am doing simulate the DDR4 crosstalk. I would have a question about the threshold voltage setting.  Currently, I choose 30mV (= 5% * Switching range = 5% * 600mV = 30mV).

      Is the setting fine? Could you please take a look at Voltage Threshold and IC characteristics below to see if they are good?

       

       

       

      Thank you, much.

        • 1. Re: Ask about DDR4 Threshold crosstalk voltage setting!
          weston_beal

          Your parameters are reasonable. Here are a few suggestions to help in your analysis.

          1- Remember that Quick Analysis is just an equation calculation, so the crosstalk is just an estimate. I use the Quick Analysis to find the potentially large errors, and then run a detailed simulation on just the nets that show large estimates of crosstalk. For the Quick Analysis, I set the threshold about 1/2 of the real threshold that I want to check. This allows for errors in the estimate.

          2- Since this is an estimate, I suggest using aggressive parameters for the Default IC Characteristics. Assume fastest strongest driver and lowest pin capacitance.

          3- The Quick Analysis can use parameters from actual IBIS models if you have them assigned to parts. Since this is DDR4, it should be fairly easy to find IBIS models. I suggest assigning the models before running Quick Analysis. This will provide better estimates of crosstalk. Then you can run full detailed simulations of the nets that show higher estimated crosstalk.

          4- The correct threshold for detailed simulation crosstalk is a matter of design impact. To start with, I suggest allowing about 1/3 of noise margin to crosstalk. If you are designing a high-reliability product, then you might use a lower crosstalk threshold. If your product is focused more on speed or low cost, then you can allow a higher threshold.

           

          I hope that these suggestions are helpful in your design and analysis.

           

          Regards,

          Weston

          • 2. Re: Ask about DDR4 Threshold crosstalk voltage setting!
            hmbui@apm.com

            Thanks much for your feedback, Weston_beal.

            Best Regards,

            Huy

            • 3. Re: Ask about DDR4 Threshold crosstalk voltage setting!
              weston_beal

              Huy,

               

              If you have a minute, could you please mark the reply with the correct answer? this will remove your question from the list of UNanswered questions.

               

              Thanks,

              Weston