During the course of a signal integrity simulation, there are an
infinite number of different waveform patterns which can emerge. One of
the responsibilities of a SI engineer is to provide meaning to these
waveforms and to evaluate their implications. To accomplish these
objectives, it is often necessary to recognize several critical waveform
characteristics (or signal integrity degradations), as defined below:
DEALY ERRORS (lack of signal transition between the high and low
thresholds within a specified period of time).
CROSSTALK (Interference caused by stray electromagnetic or electrostatic
coupling of energy from one circuit to another).
GROUND/SUPPLY BOUNCE (Source of circuit noise that occurs inside an IC
INTERSYMBOL INTERFERENCE or ISI (Distortion of received circuit,
manifested in overlap of individual pulses to the level that receiver
can not reliably distinguish between changes of state).
MULTICROSSING ERRORS (A signal passes in and out of threshold region
several times during transition).
NON-MONOTONICITY (A rising or falling waveform edge is non-monotonic, if
the edge begins to make a transition but reverses direction two or more
times before completing transition).
NOISE (Random unpredictable and undesirable signals or changes in
signals that mask desired information content).
OSCILLATION (Non-monotonic signal behavior between the high and the low
OVERSHOOT (The initial transient response which exceeds the steady state
RINGBACK (Amount by which a signal rebounds below VOH or above VOL after
an overshoot has occured).
RINGING (Transient decaying oscillation about high or low limit induced
by unmatched impedance reflections).
SETTLING BEHAVIOR (Settling time is a measure of how long it takes a
pulse to stabilize at its maximum amplitude).
SKEW (Time delay or offset between any two signals)
THRESHOLD ERRORS (A signal does not achieve the required high or low
UNDERSHOOT (Excessive voltage pulse below ground. Also called negative
It is usually desirable to specify threshold values for some of the
above signals integrity violations . For example, when using QUAD,
threshold values can be defined for logic levels, undershoot, overshoot,
noise, ground/supply bounce and crosstalk. The program then utilizes a
set of error codes (after completion of a simulation run), to report any
such signal integrity violations which may have occurred.
Signal integrity degradations, as described above, their causes (for
example reflections due to impedance miss-match, fast edge rates and
transmission line effects), their adverse effects (such as component
damage caused by overshoot, or system malfunctions due to crosstalk),
and means of eliminating them (for instance employment of an effective
temination scheme, altering topology or changing the design technology)
rank among fundamental concepts of signal integrity.
Your thoughts and suggestions are highly appreciated.
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