From: Ron Miller (rmiller@Brocade.COM)
Date: Fri May 19 2000 - 13:09:20 PDT
The medium is band limited, and has differing delays
vs frequency component(group delay) which will distort
the eye pattern. This is referred to at pattern dependent
jitter or inter-symbol interferenece(ISI).
This adds to the random jitter
Salvador Aguinaga wrote:
> Having read your reply prompts me to ask a question, though I realize it's a
> little off the subject.
> If I have a long (18" or any length for this matter) pair of point-to-point
> traces (for differential signalling) and I am no using the physical ICs to drive
> and receive the signal, does it make sense to test for Random or Data-dependent
> jitter when all I have is a random bit pattern generator driving these lines?
> Does the medium have an effect on any one type of jitter (random, RMS, etc.)?
> [By "medium" I mean the type of trace topology, impedance control, delay
> mismatch, stripline or microstrip, etc.]
> -- S. Agui
> ņaga Jr.
> Ron Miller <rmiller@Brocade.COM> on 05/17/2000 04:08:56 PM
> Please respond to firstname.lastname@example.org
> Sent by: Ron Miller <rmiller@Brocade.COM>
> To: "'si-list @silab.eng.sun.com'" <email@example.com>
> cc: (Salvador Aguinaga/MW/US/3Com)
> Subject: RE: [SI-LIST] : Point to Point Timing Budget and BER Calculations
> I cannot agree with your precept that we cannot simulate random jitter.
> NOISE ANALYSIS
> One of the biggest contributors is thermal noise which varys the voltage
> amplitude, so at the crossover it causes jitter in the waveform. Shot noise
> and similar noise sources as well as assumed EMI received on traces can
> be estimated and added to thermal noise. I think HSPICE has a means to
> add this in. ADS does for sure.
> OTHER RANDOM JITTER SOURCES
> The clock generator has random jitter but is usually specified as phase
> and is usually ~10 ps or there about.
> Digital gates can phase modulate the signal edge, but this is usually quite
> small and is caused by amplitude variations in the ICs caused again by noise
> and also by crosstalk with other signals at the gate levels.
> These are all secondary effects and are small. Random noise is the big
> in random jitter, and can be simulated.
> Ron Miller
> > -----Original Message-----
> > From: Tony Sweeney
> > Sent: Wednesday, May 17, 2000 10:16 AM
> > To: firstname.lastname@example.org.Sun.COM
> > Subject: [SI-LIST] : Point to Point Timing Budget and BER
> > Calculations
> > I have been working on several point to point applications using various
> > buffers and over various transmission line length. HPSPICE is being used
> > to model:
> > Output Buffer
> > Bondwires (coupled)
> > Package Model (coupled)
> > Board Vias (lumped)
> > Transmission line (W model coupled)
> > Board Vias
> > Package
> > Bondwires
> > Input Buffer
> > On chip power distribution is modeled for a group of outputs for SSO
> > analysis
> > A seperate clock path is also modeled and simulated with the data
> > Simulations are run over process, volatage and temp corners.
> > Different pattern sets are used to evaluate SSO, and Crosstalk. The
> > cross talk pattern is modified with the middle trace getting an Pseudo
> > Random Pattern. ISI is measured at the far end.
> > In the end, eye patterns are generated and we can see the margin in
> > setup and hold times.
> > The question is: Given we cannot simulate Random Jitter, how much margin
> > do you need to garuntee a very low BER? Can you mathmatically predict
> > BER based on a deterministic Jitter Budget?
> > If you have very small margin let's say 10ps with your deterministic
> > budget, does that mean you will have a high BER?
> > --
> > Anthony C. Sweeney
> > Field Applications Engineer
> > LSI Logic Corporation
> > 7585 Ronson Road
> > San Diego, CA 92111
> > Ph: 858-467-6980
> > Fax: 858-496-0548
> > Pager: 888-961-7562
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-- Ronald B. Miller _\\|//_ Signal Integrity Engineer (408)487-8017 (' 0-0 ') fax(408)487-8017 ==========0000-(_)0000=========== Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA 95131 email@example.com, firstname.lastname@example.org
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