[SI-LIST] Re: Jitter on serial data buses
- From: Mike Li <mli@xxxxxxxxxxxxx>
- To: ronusoalii@xxxxxxxxxxxx, damonjbowser@xxxxxxxxx
- Date: Sat, 4 Jun 2005 12:58:48 -0500
Ron:
At the end of the day, whether you think, believe, like, or dislike that
jitter is a dominant problem for serial data or not ultimately depends on
the actual experimental data for those devices on which many smart engineers
are working. Unfortunately, the data clearly indicates that jitter is,
indeed, one of the dominant problems for multiple Gb/s I/Os, particularly
for those LOW-COST, HIGH VOLUME I/Os of PCIe, FB DIMM, and SATA. If you
spend some time reading those white papers that I referenced, I hope that
you will change your mind.
Mike
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Ron Miller
Sent: Friday, June 03, 2005 12:03 PM
To: damonjbowser@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Jitter on serial data buses
Hi Damon
I may be in the minority on this but let me throw in my 2 cents.
I believe that Jitter is not the dominant problem in serial data. You hear
so much about Jitter, and very little about noise and the adjuncts that look
like noise.
Noise and the intersymbol interference, and sinusoidal components of
crosstalk
and received EMI, ground currents etc all add to form the rails we see
in an eye
pattern.
The receiver only looks at the amplitude of the differential line and
decides whether
it is a 1 or a Zero.
So, what is the impact of jitter? Jitter is only important in setting
the time that the comparator
makes its decision on a one or a zero. Typically the jitter could be 30
percent of a period
without having a sinificant impact on the Error RAte.
So, what is primary? Noise, crosstalk EMI susceptibility etc that all
occur in amplitude.
Jitter is secondary, and is important but lets get our priorities in
order. Amplitude related
effects are primary.
Ron Miller
Damon Bowser wrote:
>Hi,
>
>Does anyone know of a good reference that provides an
>overview of jittter concepts related to serial data
>buses? I'd like it to cover issues such as the impact
>of reference clock jitter on output jitter, PLL
>jitter, Tx jitter, etc. If it went into PLL circuit
>design tradeoffs for serial data buses that would be a
>plus.
>
>Thank you in advance,
>Damon
>
>
>
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--
Ronald B. Miller, Microwave/SI Engineer RAIL = NOISE + REFLECTIONS
Gigahertz Data Div of MI Corp. \\ // \\ //
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Newark, CA 94560 ->JITTER<- EYE ->JITTER<-
tel 510-793-4744, //\\ //\\
fax 510-742-6686 // \\ // \\
www.ghzdata.com RAIL = NOISE + REFLECTIONS
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