Re: [SI-LIST] : pecl termination

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From: D. C. Sessions ([email protected])
Date: Wed Jun 06 2001 - 06:31:03 PDT

On Wednesday 06 June 2001 05:25, Binoj G. S. wrote:
> I am using a differential pecl to ttl and ttl to differential pecl translator in my design in which the differential pecl o/p is using to drive one fo transceivers(hfbr 5903).As the fo transceiver i/p are in a different level I used capacitor coupling and biased the differential o\p at the fo i/p side.what I did is, biased the lines to middle of fo i/p (1.96v) with a thevenin termination which provides a 50 ohm impedance.
> But what I read is that the termination voltage should be vcc-2,i.e. 1.3v(3.3-2).How can I satisfy both of this condition or I am doing something false?The fo I/p levels are as follows
> vil min-1.49v vil max-1.825 vih min-2.135 vihmax-2.42

The termination to VCC-2 is in the context of open-source drivers
(ECL open emitters, NMOS open sources, or PMOS open drains.)
In your case, you want to terminate to VCC-1.32 volts which is
the center of the common-mode range.

| I'm old enough that I don't have to pretend to be grown up.|
+----------- D. C. Sessions <[email protected]> ----------+

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