Re: [SI-LIST] : 3.3v and 2.5v LVDS

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From: Bill.Cohen@taec.toshiba.com
Date: Thu Apr 05 2001 - 14:19:04 PDT


sreejith,

It should be no problem. The LVDS standard is fully differential.
The differential signals are centered about 1.2V without regard
to the power supply. The common mode differential voltage is
0V to 2.4V. For our 2.5V LVDS receiver we went to rail
to rail input common mode architecture. The driver delivers
a differential voltage at 1.2V well below either the 3.3V or
2.5V supplies.

One slight problem that might be encountered with the 2.5V
receiver is that there is really no way to sense that the
signal is disconnected. The LVDS specification states that
an open circuit on the receiver inputs should be sensed. When
the input range spans the power supply range this sensing
is virtually impossible in hardware. With a 3.3V power supply
a sensing circuit can be use that pulls the inputs out of
the common mode range. This open circuit condition can be sensed.
Usually with most users of LVDS this is not a big problem.

Bill Cohen
Circuit Design
Toshiba America Electronic Components
Marlborough MA

"Sreejith Varma" <varma@blr.paxonet.com>@silab.eng.sun.com on 04/05/2001
01:31:58 PM

Please respond to "Sreejith Varma" <varma@blr.paxonet.com>

Sent by: owner-si-list@silab.eng.sun.com

To: <si-list@silab.eng.sun.com>
cc:
Subject: [SI-LIST] : 3.3v and 2.5v LVDS

HI All,

do any one have info on interfacing between a 3.3v LVDS device and
a 2.5V LVDS device.

regards
sreejith

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