[ibis-macro] Re: Question about "impulse response"

  • From: Mike Steinberger <msteinb@xxxxxxxxxx>
  • To: ibis-macro@xxxxxxxxxxxxx
  • Date: Mon, 6 Nov 2017 12:19:25 -0600


It appears that although I composed the message, I did not manage to send it. My apologies.

If in your example what you mean by a 400mV swing in a differential Tx buffer is that the True pin swings from a single ended voltage of Vref-200mV to a single ended voltage of Vref+200mV, and similar for the Comp pin, then a logic "0" would have a differential output voltage of -400mV, a logic "1" would have a differential voltage of +400mV, and the differential voltage swing between "0" and "1" would be 800mV, as you describe. Is this what you meant?

I'm afraid that when we're trying to track down factors of two, our best chance of success is to be this pedantic.

Mike S.

On 11/06/2017 11:59 AM, Muranyi, Arpad wrote:


I don’t think I saw that response.

Could you please resend it?




*From:*ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike Steinberger
*Sent:* Monday, November 6, 2017 11:54 AM
*To:* ibis-macro@xxxxxxxxxxxxx
*Subject:* [ibis-macro] Re: Question about "impulse response"


I responded to your e-mail will a clear and complete interpretation of your example- an interpretation, by the way, which concluded that you were off by a factor of two. I never did get any response to that e-mail, so maybe it somehow didn't make it into your in-box.

Do I need to resend that e-mail?

Mike S.

On 11/6/2017 11:41 AM, Muranyi, Arpad wrote:


    I think I gave all that information in my illustration, which is
    now on

    the bottom of this email.  Please let me know if that is not clear and

    I will try another way…




    [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike
    *Sent:* Monday, November 6, 2017 11:31 AM
    *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
    *Subject:* [ibis-macro] Re: Question about "impulse response"


    Is the 800mV swing a single ended voltage swing or a differential
    voltage swing? The input signal to the receiver is a differential
    voltage. If we confuse single ended with differential, we'll be
    mixing apples and oranges, and end up with a dog's breakfast.

    I cannot agree to Todd's interpretation until I get your answer to
    this question.

    Mike Steinberger

    On 11/6/2017 11:11 AM, Muranyi, Arpad wrote:


        Thanks for that clarification.  Yes this is with the
        assumption that

        the IR is derived from a step response, but all other methods

        would need to provide equivalent results…

        Would everyone on this email list agree with Todd’s




        *From:*Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
        *Sent:* Monday, November 6, 2017 10:33 AM
        *To:* Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx>
        <mailto:Arpad_Muranyi@xxxxxxxxxx>; ibis-macro@xxxxxxxxxxxxx
        *Subject:* RE: [ibis-macro] Re: Question about "impulse response"


        My interpretation is that the channel impulse response passed
        to Tx_Init will be the result of differentiating the 800 mV
        differential step response, as you say.

        That, of course, is assuming that the impulse response is
        derived from a step response and not through some other method …


        *Todd Westerhoff*

        VP, Semiconductor Relations

        Signal Integrity Software Inc. • www.sisoft.com

        6 Clock Tower Place • Suite 250 • Maynard, MA 01754

        (978) 461-0449 <978-461-0449> x124  • twesterh@xxxxxxxxxx

        *“*I want to live like that”

                                                     -Sidewalk Prophets

        [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of
        *Muranyi, Arpad
        *Sent:* Thursday, November 2, 2017 2:27 PM
        *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
        *Subject:* [ibis-macro] Re: Question about "impulse response"


        I am trying to apply what you are saying to IBIS-AMI. Let’s
        use an example in which

        the differential Tx buffer has a 400 mV voltage swing on each
        of its outputs, and as a

        result, the difference step waveform at the Rx goes from -400
        mV to +400 mV (i.e.

        the amplitude of the step waveform is 800 mV).  The simulator
        will differentiate this

        step waveform and pass it into the AMI Tx Init function as the
        impulse response of

        the channel (or convolve with the output of the Tx GetWave
        function for the time

        domain AMI simulation).  Is this the correct interpretation of
        “impulse response” in

        the IBIS-AMI specification?  Or should the 800 mV difference
        step waveform be

        divided by 2 first before differentiating it to become the
        “impulse response” for the

        purposes if AMI simulations?




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