MODELING AND BUDGETING OF TIMING JITTER AND NOISE - Advanced Signal Integrity for High-Speed Digital Design - page 557

Total Jitter

Random
Jitter (RJ)

Characteristics
• Unbounded, Gaussian distributed

• Key parameters: m = 0, s RMS

• Sources: Device noise (shot, flicker, thermal)

Characteristics
•

Deterministic
Jitter (DJ)

Bounded, peak-to-peak

• Key parameters: Maximum pk-pk jitter

• Sources: Losses, reflections, t r / t f mismatch,

Sinusoidal
Jitter (SJ)

spread spectrum clocking, crosstalk

Data Dependent
Jitter (DDJ)

Intersymbol
Interference (ISI)

Duty Cycle
Distortion (DCD)

Bounded
Uncorrelated Jitter
(Crosstalk)

Figure 13-10 Summary of jitter types and their characteristics.

random jitter values at several standard deviations from the mean is extremely
low. Random jitter is caused by device effects such as thermal noise and shot
noise (see Section 13.4.1). Random jitter shows up as the “tails” of the jitter
distribution, and we use it to budget peak-to-peak jitter as a function of BER, as
we describe in the material that follows. As we shall see, the amount of RJ (in
terms of the number of sigma) that we must take into account increases as we
decrease the target BER.
Deterministic jitter traces to specific causes and is bounded, meaning that the
probability of exceeding the peak-to-peak maximum value is equal to zero. We
can categorize DJ in terms of sinusoidal or periodic jitter (PJ) and sources of
data-dependent jitter (DDJ). Data-dependent jitter, as its name suggests, depends
on the data pattern that is being transmitted. Prominent types of DDJ include
duty-cycle distortion (DCD), intersymbol interference (ISI), and crosstalk. We
describe each source in the paragraphs that follow.

Periodic Jitter PJ repeats at a fixed frequency and is caused by modulating
effects, such as spread-spectrum clocking. For a system with multiple periodic
sources, we model the total periodic jitter as

PJ(t) = A i cos (ω i t + θ i ) (13-10)

i