[SI-LIST] Re: Series termination

Are you planning on using a "current steering" approach for your driver? =
 If
so, I don't think I've ever seen series termination on the outputs, . . =
.
only parallel termination.

If you want to add real resistance to your output impedance, in addition =
to
the impedance of the transistors switching, . . . most people place the
resistors on-chip in series with the current source (as opposed to in =
series
with the output pins).

Regards,

Patrick

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On
Behalf Of Vinayak AGRAWAL
Sent: Monday, December 27, 2004 3:49 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Series termination

Hi

I am designing a transceiver that will use series termination. The IO is =

a differential driver, so while one pin will be connected to high=20
voltage (external pin) through a series resistor of 50ohms, the other=20
will be connected to gnd (and the connectivity switches to toggle the=20
output) the same way.

when I started design I thought it should be good enough to terminate in =

this way, because I had seen many single-ended (as opposed to=20
differential) drivers doing the same. However now I'm worried whether=20
the differential termination will be good enough for a 100ohm =
termination.

Specifically I'm concerned about the return path for the current. As I=20
see it, it is something like: into the negative pin, through 50ohm, gnd, =

gnd-vdd coupling, vdd, 50ohms resistor, positive going pin. I doubt=20
whether gnd-vdd coupling will be good enough for high speed data=20
transfer (300-6000Mbps). On the other hand I believe similar issues=20
should come for single-ended drivers.

Can someone point to any reading material. Also any criticisms of the=20
approach are welcome.

Regards
Vinayak

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20




------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: