[SI-LIST] [Help] How to do termination in differential signal with series termination ?

  • From: "King Da" <yardala@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Fri, 5 Dec 2008 10:59:20 +0800

Hi,Folks,
I have a differential pair which odd mode impedance is 48 Ohm and even mode
impedance is 108 Ohm by TDR measurement.
I would like use 100 Ohm for differential termination at far end, but how to
choose series termination resistor for each trace at near end?

I refered Bogatin's "Signal Integrity:Simplified" book that said parallel
termination R2 equal Zeven, So, I should use 108 Ohm subtract 20 Ohm of my
driver's Ro is 88 Ohm for my series termination at near end, am I right?

The Rseries = 108 (Zeven) - 20 (Driver's Ro) = 88 Ohm, right ?

Does the differential termination resistor is 100 Ohm better than 91Ohm ?

Thanks,

Yardala


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