Re: [SI-LIST] : PECL oscillator termination

About this list Date view Thread view Subject view Author view

From: Michael Nudelman ([email protected])
Date: Thu Nov 09 2000 - 12:50:00 PST

Tae-Kwang Jeon wrote:

> Hello everyone,
>
> Here's a question on 3.3V PECL osc. termination.
>
> I know that a Thevenin termination is used on the diff'l outputs of the osc.
> But, what i'm concern is the case of AC-coupling to a 50ohm termination.
> The qestions occurred to me are;
> #1 Is there any recommended value of the coupling cap?

0.1uF is OK

>
> #2 How to size the resistors to DC-bias the PECL outputs? Is there also
> any recommended range of size?

330 Ohm typical.

>
> #3 In the case of #2, the resistors are supposed to be grounded, then what
> if I make them in series?
>

In series with what? WIth the praces of the diffpair?
The resistors are there to provide bias. Make them in series with the pair - and
you divide your signal between your resistor and the trx-line. The series
termination does just that, but then, if you need AC-coupling, wher's your bias?
YOu will open can of worms, when everything is simple - connect 330 Ohm to GND,
run your traces, put the caps in series (where you like; some people have
different preferences - beginning, end) and terminate - either for diff. mode
(diff. impedance resistor between traces in the end) of for common mode (one
trace impedance resistor to GND from each trace in the end).

Mike.

>
> Any comments would be appreciated.
>
> Regards,
> TK
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> TaeKwang Jeon, LSI Logic Corp.
> 1525 McCarthy Blvd Phone: (408) 433-6818
> MS G-715 Fax : (408) 433-2840
> Milpitas, CA 95035 Email: [email protected]
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> [email protected]. 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
[email protected]. 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 : Tue May 08 2001 - 14:30:01 PDT