Course Goals
The attendee shall walk away knowing...
- A clear understanding of jitter terminology.
- How to identify the type(s) of jitter important for your application.
- The different ways to view jitter and what each reveals about the underlying source(s) of jitter.
- How jitter propagates through a high-speed serial link, and how standards specify jitter to limit it.
- How to select the right test equipment and use it to measure jitter in your end application.
Course Outline
Part 1: Understanding Jitter
Jitter as a branch in signal integrity. Timing and amplitude noise. Jitter versus skew, wander, AC timing noise, DC timing noise. Various definitions of timing events.
Market forces impacting jitter today and how this effects you. Trend analysis: serial links, high-speed design, process technology, small form-factor pluggable optics.
Current noise versus voltage noise. Shot, thermal, flicker noise. Reflections, crosstalk, EMI, and AM to PM conversion.
Time-interval error, period jitter, half-period jitter, cycle-to-cycle jitter, N-cycle jitter, N-cycle to cycle jitter, half-period cycle-to-cycle jitter, dynamic phase offset, phase noise, phase jitter, interval jitter, accumulated jitter, absolute jitter, intrinsic jitter, extrinsic jitter, short-term jitter, long-term jitter, tracking jitter, edge-to-reference jitter, edge-to-edge jitter. A framework is constructed to organize jitter in a perfectly clear manner.
Which jitter does your application care about and why? Clocks driving synchronous logic, DDR synchronous logic, pixelated systems, downstream PLLs, PLLs for on-chip deskewing, serial-bus TX PLLs, serial-bus RX PLLs, data converters. Parallel versus serial buses. PLLs used for achieving zero-delay. Oscillators. PLLs. Spread spectrum modulation.
Understanding and working with histograms, eye diagrams, phase-noise graphs, and each of their associated units for reporting jitter.
Random versus deterministic jitter. Gaussian distributions. PDFs, CDFs, histograms, RMS and standard deviation. Data-dependent jitter, periodic jitter, duty-cycle dependent jitter, bounded uncorrelated jitter. Sources of jitter. Total jitter concept. Common pitfalls. Ways to organize jitter terminology to keep everything clear.
Anatomy of serial-bus links. Jitter generation, jitter transfer, jitter tolerance, bit-error rate, PRBS, clock/data recovery, jitter filters. Common test set ups, and measurement points. Calculating BER from Gaussian statistics. Converting RJ RMS to peak-peak using BER. Analysis of BER when Strobe is off-centered. Bathtub plots.
Part 2: Working with Jitter
Reading between the datasheet lines (keeping device manufacturers honest... real-world examples).
Converting phase noise (dBc/Hz) into phase jitter (ps RMS)... when you have a large dataset ...when you have a limited dataset. Free tools available for use. How to deal with spurs. Common methods, and why you shouldn't use them.
Visualizing the relationship between phase jitter, period jitter, and cycle-to-cycle jitter.
Useful assumptions you can make to gain insight into your measurements.
How to add jitter from multiple sources. Assumptions you didn't know you were making. Estimation versus exact calculation (which one to use?).
How to create a useful jitter budget. Example physical-layer budget. PCIe case study. Assumptions being made.
Inner workings, comparisons, tradeoffs, and recommendations: Digital sampling oscilloscopes, equivalent-time and real-time oscilloscopes, time-interval analyzers, bit-error ratio testers, spectrum analyzers, phase-noise analyzers, pulse generators. How many bits to measure for BER. One-port versus two-port phase-noise measurements. Working with phase-noise plots.
Why decompose jitter? Dual-Dirac. Spectral Decomposition. Histogram Tailfitting.
Best practices in designing system/ PCBs/chips. How to set up your real-time scope for low-jitter measurements.
Using PLLs to filter jitter. Avoiding problems with cascading PLLs. Insight from jitter transfer plots. How to propagate jitter through a PLL.
Who Should Attend?
Anyone exposed to jitter on a regular basis will benefit from this course. |
