[SI-LIST] Re: [Help] How to do termination in differential signal with series termination ?
- From: "DAVID CUTHBERT" <telegrapher9@xxxxxxxxx>
- To: "King Da" <yardala@xxxxxxxxx>
- Date: Thu, 4 Dec 2008 20:38:18 -0700
Make the differential driver impedance 100 ohms. That is 50 ohms for each
driver. With the 20 ohm driver IC impedance use a series 30 ohm at each
driver IC.
Dave Cuthbert
On 12/4/08, King Da <yardala@xxxxxxxxx> wrote:
>
> 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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