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Advanced High-Speed Signal Propagation

The seminar Advanced High-Speed Signal Propagationis designed for experienced digital designers who need to press their designs to the upper limits of speed or distance. It complements the introductory course, High-Speed Digital Design.

The main topics include a thorough examination of lossy and dispersive effects on transmission lines, taken in the context of a high-speed serial link, discussion of pcb routing rules related to differential signaling, s-parameters, clock jitter, and compensation for transmission-line disturbances.

This is a practical course, filled with practical examples and explanations. Delegates without the benefit of formal training in analog circuit theory can use and apply the formulas and examples from this course to determine which of their circuits will encounter difficulties and how to fix them.

Delegates who have completed (at least) a first-year class in introductory linear circuit theory will comprehend the material at a deeper level.

The course builds on material presented in the introductory course. If you are not sure whether you are ready for the advanced class, try this pop-quiz (ten questions).

Quiz

The following material is covered in the course "High-Speed Digital Design". If you have already taken that class, or you make 70% or better on this quiz, you are ready for the advanced course. If you score less than 70%, you may, of course, still attend, and you'll learn a lot, but you will comprehend the material at a deeper level if you first take Dr. Johnson's original course,High-Speed Digital Design.

Answers appear at the end of the quiz.

1. In a synchronous digital system, the highest frequency of interest for purposes of signal integrity is approximately:
   1. The velocity of signal propagation divided by the signal path length
   2. One-half divided by the rise or fall time of the signal, whichever is less
   3. The third harmonic of the clock
   4. The processor's internal clock frequency
   5. The fifth harmonic of the clock
2. Which of the following trace configurations is the fastest:
   1. Microstrip with heavy soldermask
   2. Stripline
   3. Offset stripline
   4. Embedded microstrip
   5. Microstrip with no soldermask
3. When two fifty-ohm traces rise out of the plane of the pc board and flow through the air (as when passing through connector pins or component bodies) the resulting crosstalk is caused mostly by:
   1. Far-field radiation
   2. Inductive coupling
   3. Electron leakage currents
   4. Aluminum migration
   5. Capacitive coupling
4. What can happen when you violate the setup and hold times on a flip flop?
   1. The Q output goes to a voltage halfway between zero and one and stays there
   2. The output assumes an imaginary value equal to 1+j
   3. The flip-flop loses sync., causing a series of errors
   4. Output transitions occur much later than the specified CLK->Q interval
   5. The flip-flop circuit burns up
5. In which way is a single-ended oscilloscope probe NOT likely to distort your signal:
   1. The input capacitance of the probe loads your signal
   2. Non-linearity in the vertical amplifier makes rising edges appear earlier than falling ones
   3. The limited bandwidth of the probe distorts and slows the shapes of rising and falling edges
   4. The dc input resistance of the probe draws extra drive current from your circuit
   5. The inductance of the ground wire associated with the probe sets up a resonance
6. On a long transmission line, the value of an external series-terminating resistor should equal:
   1. The load resistance of the receiver minus the source resistance of the driver
   2. 17 ohms
   3. The smallest value that stops ringing just before the clock setup time
   4. The transmission line Z0 minus the source resistance of the driver
   5. 33 ohms
7. A diode-clamping termination at the end of a trace can sometimes improve signal quality, but never does as well on a long transmission line as:
   1. A resistor in the middle of the line
   2. An "H" distribution
   3. Modulating the line width
   4. The R-C termination (resistor and capacitor in series)
   5. A purely resistive termination at the source, end, or both
8. What is the primary effect of an interruption (hole or slot) in the reference plane underneath a high-speed trace?
   1. Decreases power-supply noise
   2. Weakens the physical board structure, causing warping
   3. Increases crosstalk among all traces that cross the same hole or slot
   4. Prevents signal from crossing the hole or slot
   5. Exacerbates the "swiss cheese" effect
9. Which of the following adjustments would increase the lead inductance of a surface-mounted bypass capacitor?
   1. Changing the layout to use a smaller component body
   2. Moving the power and ground planes closer to the surface of the board where the capacitor sits
   3. Adding more vias
   4. Using fatter vias
   5. Adding traces in series with the mounting pads
10. At the end of an unterminated transmission line, a ringing waveform tells you that:
    1. The source impedance of the driver is too low
    2. The Z0 of the transmission line is too low
    3. The receiver has too much inductance
    4. The source impedance of the driver is too high
    5. It's Miller time

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