Re: [SI-LIST] : PECL Clocks.

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From: Nianci Wang (nwang@amcc.com)
Date: Fri Feb 16 2001 - 12:33:25 PST


In general, the star style should always work if you have a proper termination
at the end of oscillator transmission line and keep the traces from termination
to SerDes clk pin very short (for 77.76MHz, the traces should be less than 1.5
inch). But daisy chain style may not work depend on how larger the SerDes chip
package parasitic and how long your transmission line from clock driver to
SerDes chip.

Hope this will be help

Nianci

"Ingraham, Andrew" wrote:

> Try simulating it. In principle, you can drive some number of devices from
> one ECL/PECL source, parallel terminated after the last receiver. However,
> sometimes you can end up with plateaus or glitches right in the middle of
> the waveform, which is not good for clocks.
>
> Try various combinations and routing methods; for example, star vs.
> daisy-chain, long and short traces, etc. Occasionally the one that you
> thought wouldn't work, actually looks the best.
>
> Andy
>
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