[SI-LIST] Re: impedance mismatch
- From: Chris Landrum x311 <clandrum@xxxxxxxxx>
- To: "'hfgong@xxxxxxxxxxxxxx'" <hfgong@xxxxxxxxxxxxxx>
- Date: Fri, 7 Nov 2003 08:57:26 -0500
True...if they are close enough... If they are close enough, and the
rise/fall time is slow enough....you may not need a termination at all.
-----Original Message-----
From: Gong hai feng [mailto:hfgong@xxxxxxxxxxxxxx]
Sent: Thursday, November 06, 2003 9:56 PM
To: clandrum@xxxxxxxxx
Cc: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: impedance mismatch
I agree with VS. In case of IC2 is TX, since it matchs the TL, the
refections from RX (IC1) will be terminated at IC2 side, and IC1 still
could have a good waveform as long as Rs is close enough to the IC1. It
could be verified by simulation.
Best regards,
H.F.
----- Original Message -----
From: Chris Landrum x311 <clandrum@xxxxxxxxx>
Date: Wednesday, November 5, 2003 10:29 pm
Subject: [SI-LIST] Re: impedance mismatch
> No, it won't. For source series termination it is important to
> have the
> series resistor at the source so that the resistor can dampen the
> reflectionthat bounces off of the destination.
>
> At any rate...simulation is the best way to go.
>
> -----Original Message-----
> From: V S [mailto:for_si2003@xxxxxxxxx]
> Sent: Wednesday, November 05, 2003 9:27 AM
> To: clandrum@xxxxxxxxx; 'si-list@xxxxxxxxxxxxx'
> Cc: 'dominic.kin.hii.chin@xxxxxxxxx'
> Subject: Re: [SI-LIST] Re: impedance mismatch
>
>
> <Assuming that IC1 is the source and IC2 is the
> receiver ALL OF THE TIME, I would simply series
> terminate the transmission line as close to IC1 as
> possible.>
>
> I believe the result will hold good even if IC2 is the
> transmitter and IC1 is the receiver.
>
> Simulation should be performed for confirmation.
>
> V S
>
>
> --- Chris Landrum x311 <clandrum@xxxxxxxxx> wrote:
> > Assuming that IC1 is the source and IC2 is the
> > receiver ALL OF THE TIME, I
> > would simply series terminate the transmission line
> > as close to IC1 as
> > possible. A 25 Ohm resistor should make up the
> > difference.
> >
> > -----Original Message-----
> > From: Chin, Dominic Kin Hii
> > [mailto:dominic.kin.hii.chin@xxxxxxxxx]
> > Sent: Wednesday, November 05, 2003 3:05 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] impedance mismatch
> >
> >
> >
> >
> >
> > Hi experts,
> > I am doing PCB design to communicate IC1 to IC2. The
> > termination of
> > these ICs:
> >
> > IC1 buffer: 25 ohm
> > IC2 buffer: 50 ohm
> >
> > If I use a 50 ohm trace, there will be impedance
> > mismatch and reflection
> > at IC1 or vice versa. How should I design PCB to
> > cater for these
> > different terminated impedance ICs?=20
> >
> > Thanks
> > Dom
> >
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