Re: [SI-LIST] : driving into 50 Ohm impedence

About this list Date view Thread view Subject view Author view

From: David Instone (david_instone@uk.xyratex.com)
Date: Fri Mar 09 2001 - 01:44:26 PST


Shripadaraj,
   Sound like a PECL device to me. Terminate each side of the
differential output to Vdd-2.0V using a 50 ohm resitive load. Each
side of the output should then have a total swing of 900mV measured
across that load, giving 1800mV p-p measured between the two outputs.
The 50 ohms to Vdd -2 can be done using 50 ohms to a voltage supply at
Vdd-2 which can sink current to ground or by use of a thevenin euivalent
resistance of 50 ohms from a potential divider across the supply rails,
or a combination of the two.

However, you say it is a Fibre Channel device, possibly, but be aware
that FC operates at 1.0625 Gbps (or 2.125) and is specified as a 75/150
ohm system, the 50 ohm resistors would be 75 ohms. Gigabit Ethernet
operates at 1.25 Gbps and is also a 75/150 system. However, some IC
manufacturers also specify their drivers at 50 ohms, as some system
builders prefer to operated FC at 50/100 ohms inside their equipment.

Hope this helps

-- 
Regards

Dave Instone. Compliance Engineer Storage Systems Development, MP24/22 Xyratex, Langstone Rd., Havant, Hampshire, P09 1SA, UK. Tel: +44 (0)23-92-496862 (direct line) Fax: +44 (0)23-92-496014 http://www.xyratex.com Tel: +44 (0)23-92-496000

SHRIPADARAJ AD wrote: > > Hi all SI expert, > > This may be a silly question, but not for me. > > I have a fibre channel transceiver operating at 1.2 Gbps data rate. It has differential o/p and o/p level specs are as below, > > 1800 mV(p-p) driving 50 Ohm to VDD-2.0v. > > What does it mean ? I am novice to this field. > > I have beeen given spice netlist of the o/p driver and asked to verify that driver meet about voltage level requirement. How should do that ? > > Any pointers in this regard would be of great help to me > > Thanks in advance > > Shripad > > _____________________________________________________ > Chat with your friends as soon as they come online. Get Rediff Bol at > http://bol.rediff.com > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jun 21 2001 - 10:11:09 PDT