[SI-LIST] Re: Rise time calculation

Good Morning all,
here are my two cents to the topic.

It's been observed by practice (and also proved mathematically) that a
series termination adds up to propagation delay and also slows down the fast
rising edges.
Some amount of mathematics can be used to prove that propagation delay
introduced by series termination is double the propagation delay introduced
by the parallel termination.

Following equations might help you on this front;

If Zo is the intrinsic impedance of the trace (transmission line), Ct is the
Thevenin equivalent load capacitance and
Tpd is the propagation delay of the trace,

        then:
                        Tpd = 0.70 X Zo X Ct, for a series terminated line and
                        Tpd = 0.35 X Zo X Ct, for a parallel terminated line.

        Some more mathematical calculations provide the following results;

If Tri is the input rise time, (ie., Rise time of the source) and Tro is the
output rise time(at the output end of  termination resistor),

        then:

                        Tro = (Zo X Ct) X ln [ {(Zo X Ct)/(0.18 X Tri)} X 
[{e^{(1.2 X Tri)/(Zo X
Ct)}-1}],
                        for Series terminated line.
        and
                        Tro = {(Zo X Ct)/2} X ln [ {(Zo X Ct)/(0.36 X Tri)} X 
[{e^{(2.4 X
Tri)/(Zo X Ct)}-1}]
                        for parallel terminated line.

Hope this will help.

Best Regards
Subramanya C K
Wipro Technologies, Bangalore- India



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jinto N.Jose
Sent: Monday, July 30, 2001 3:12 PM
To: SI List
Subject: [SI-LIST] Rise time calculation



Hi all,
        How should I calculate the rise time at the receiver of a series 
terminated
signal ? What all parameters I need to know for doing this calculation ?



  Driver         Trace of known
   |\    Rs      impedance & length  |\
   | \__/\/\/\__|------------------|_| \
   | /          |------------------| | /
   |/                                |/
                                   Receiver


     I want to calculate the rise time at the receiver input.

Thanks
Jinto





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