12 Replies Latest reply on Apr 17, 2013 10:00 AM by jtorres

    Gigabit ethernet with transformer


      Hello guys,

      can somebody recommend me some solution concerning the circuit with a gigait IC and transformer  to be able to simulate it?

      It is clear I have to have a simulation models - let's say I have only a (IBIS) model of IC... not of transformer.... shall I find S-parameter??

      Can somebody recommend me the aproppirate type of transformer with its model I can use in HyperLynx?


      ... or there is another way how to replace transformer for simulation issue?


      Many thanks


        • 1. Re: Gigabit ethernet with transformer

          If you can get either a Touchstone S-parameter model or a SPICE model of the transformer then you can use that to simulate your net in HyperLynx. There are technotes and application notes on SupportNet to help you understand the steps for this. The HyperLynx user manual is quite helpful, too. Generally, the bigger problem is getting an adequate model of the IC.



          • 2. Re: Gigabit ethernet with transformer

            Thanks you Weston,

            I don't have enough time to read much documents right now...

            So I got a "SPICE" model of one transformer in pdf.

            Is there some easy way what shall I do with it to be able to use it as fast as possible in HyperLynx SI?


            Many thanks


            • 3. Re: Gigabit ethernet with transformer

              Copy-paste it into the text file and you'll have a SPICE model. In HL there is a component (connector?) into which a SPICE model can be mapped.

              • 4. Re: Gigabit ethernet with transformer


                I thaugh the same and did it.

                I saved the file with extension sp , I saw it in "Assign Package" dialog but this model doesn't have any ports.... see my picture. Not possible click OK button.

                What I did wrong?

                Any hint?



                • 5. Re: Gigabit ethernet with transformer


                  You should teak the circuit file in pdf to make a subckt file. To teak spice, it's a must to know spice concept..




                  • 6. Re: Gigabit ethernet with transformer



                    Any success simulating the giga ethernet?

                    • 7. Re: Gigabit ethernet with transformer



                      Simulating GigE is no different than 10/100 BASE-T as long as you have the proper models.


                      Please see the attached sample EZWave waveforms. All the simulations have been performed using HyperLynx v9.0 Beta 3.



                      • 8. Re: Gigabit ethernet with transformer



                        Thank you for your replay.

                        In some variations 1G ethernet works on 5 levels of voltage. I have a previous version of HyperLynx and I'm not familiar with v9.0. Is there a model to generate those levels?



                        • 9. Re: Gigabit ethernet with transformer

                          Hi Ronen,


                          You are right, 1000Base-T uses PAM5 differential line signaling with more than five voltage levels (+1, +0.5, 0, -0.5, -1 and more due to the other end TX), while 100Base-TX uses MLT-3 differential signaling with three voltage levels (+1, 0, -1). The block encoding is 4B/5B in the case of 100Base-TX and 4D-PAM5 in the case of 1000Base-T. However when you perform Time Domain characterization of the link there is no way to know if the response is adequate or not, if you use random stimulus. This is why the IEEE Std 802.3 defines four Transmitter test modes for 1000Base-T compliance tests. These modes are enabled by setting bits 9.13:15 if the device is equipped with a GMII interface. The Standard defines also the core tests that one should use for compliance measurements:


                          ·         Differential output template tests

                          ·         Peak differential output voltage level and accuracy tests

                          ·         Droop tests

                          ·         Distortion

                          ·         MDI Return Loss

                          ·         MDI Common-mode output voltage test

                          ·         MASTER/SLAVE Jtxout measurements

                          ·         Bit Error Rate verification

                          ·         Data rate


                          For each of those tests there are limits that you can check against. Please see the standard for more details.


                          For simulation purposes, usually behavioral buffer models can output test mode 1 and 2 stimulus. Test mode 1 stimulus is useful for measuring output amplitudes, amplitude symmetry and pulse drop.


                          You can also perform Frequency Domain simulations of the channel (MDI Return Loss). The spec defines the following limits:

                          ·         ≥ 16 dB from 1MHz to 40 MHz

                          ·         ≥10-20LOG(f/80)dB from 40 MHz to 100 MHz, where “f” is in MHz.


                          I have attached for you an example of a plot that shows the MDI differential return loss (SDD11). You can use “Targets” (HL v.9.0) or “Guidelines” (HL v. 8.2) to help you to visually check against the limits.


                          If you have the real hardware you can use Tektronix Ethernet Compliance Test Software (TDSET3) installed on an oscilloscope to perform those tests either in TD or FD. I have attached few sample waveforms from measurements for your convenience.


                          I hope this helps,


                          • 10. Re: Gigabit ethernet with transformer



                            Thank you very much Cristian. You have been a great help.

                            I will look into it.

                            Do you happen to know if there is a way to get a simulated eye pattern?

                            • 11. Re: Gigabit ethernet with transformer

                              Hi Ronen,


                              As far as I know you need a modulated random-data pattern to generate en eye pattern of a PAM-5 signaling and I guess that this is not easy to implement in Spice (and match the real silicon behavior). I personally haven’t yet come across those types of models.


                              However maybe somebody from Mentor has a better answer to this question.



                              • 12. Re: Gigabit ethernet with transformer

                                Hi guys,


                                I'm trying to perform some simulations of a Ethernet 100-base-T or 1000-base-T channel, and I cannot get an ibis model for the differential physical layer side of those transceivers, the models only include the MII/RMII interface and control signals.

                                By contacting the mentor support, I got the following answer:


                                "Ethernet uses multi-level signaling, so we don’t really simulate it  in HyperLynx (although I guess you could set up a SPICE simulation in HyperLynx  to do it).


                                If it  is a SERDES link inside a switch or something, it works like any other SERDES  bus.


                                For  most applications, though, Ethernet routes are extremely short on the board, and  actually somewhat “forgiving” (since it will run over 100m of twisted-pair  cable).


                                Because  of this, most Ethernet simulation work, if any, is done on the S-parameter  level, looking at things like insertion loss, return loss, and crosstalk.  I  believe Ethernet has some specs for these that need to be followed on the board  level.  You can use HyperLynx to extract S-parameters to compare to the  spec"


                                Did any of you managed to perform simulations in this case?