# [ibis-macro] Re: another silly IBIS-AMI question about deriving the impulse response of a channel

• From: Scott McMorrow <scott@xxxxxxxxxxxxx>
• To: Walter Katz <wkatz@xxxxxxxxxx>
• Date: Thu, 27 May 2010 18:52:03 -0400

 Walter Modern Transmitters and receivers utilize compensation networks to effectively isolate receiver and ESD input capacitance from the pad of the device.  A common structure is known as a T-coil, a three terminal network. The high impedance input to a receiver is represented by the capacitively loaded center tap of the two inductors.  The left side of the circuit is the die input. On the right side of the circuit is the Resistor.  In order to correctly compute the frequency domain transfer function from diePad to receiver gate input, you have to drive the pad side with a 50 ohm characteristic impedance, and the center Tap with the high impedance of the receiver.  Conversely, to simulate this in the time domain the termination resistance must be included as Rt in the circuit, but the waveform must be monitored by an infinite impedance probe at the Center Tap Vout. Scott On 5/27/2010 6:31 PM, Walter Katz wrote: Scot,   I think a better picture is:   TxTerm --- TxDie --- TxBump -- TxPkg -- channel -- RxPkg -- RxBump -- RxDie --- RxTerm   |                                                                               |   |                                                                               | TxPad                                                                           RxPad Walter       Walter Katz 303.449-2308 Mobile 720.333-1107   -----Original Message----- From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx] Sent: Thursday, May 27, 2010 6:25 PM To: Walter Katz Cc: IBIS-ATM Subject: Re: [ibis-macro] another silly IBIS-AMI question about deriving the impulse response of a channel   Walter, You are misinterpreting my picture.  I was showing the network of just a Tx or Rx.  When I say "network" I truly mean a circuit network.  Let me create a better picture of the entire channel. TxTerm --- TxDie --- TxBump -- TxPkg -- channel -- RxPkg -- RxBump -- RxDie --- RxTerm              |                                                          |              |                                                          |            TxPad                                                       RxPad For a 50 ohm single-ended channel TxTerm = 50 ohm RxTerm = 50 ohm TxPad = some high impedance RxPad = some high impedance Lumped approximations between TxTerm/TxPad and RxTerm/RxPad do not hold What I was showing was just one part of the total channel. (50 ohm)RxBump --- Network --- RxTerm (50 ohm)                       |                        |                     RxPad                    (10k ohm)                ```-- Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC ```
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