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Ground bounce, crosstalk, impedance matching, skew

Short answer

Ground bounce: transient voltage from simultaneous switching currents across package inductance (V = L·di/dt) causing false logic. Crosstalk: unwanted capacitive/inductive coupling between adjacent traces, reduced by spacing and ground plane. Impedance matching: equalizing source, line, and load impedances to avoid reflections. Timing skew: difference in signal arrival times due to unequal trace lengths; match lengths.

Write about ground bounce, cross talk, impedance matching and timing skew.

Ground bounce

When many outputs of a chip switch together, a large transient current flows through the inductance of the ground (and power) lead and pin. The voltage developed, V = L·di/dt, raises the local ground above the system ground for a short time, which can cause false logic levels on quiet outputs. Reduced by decoupling capacitors, short and wide ground paths, ground planes and by limiting simultaneous switching.

Crosstalk

Unwanted coupling of signals between neighbouring traces by mutual capacitance (I = C·dV/dt) and mutual inductance (V = M·dI/dt). Reduced by larger spacing (3W rule), shorter parallel length, ground plane or guard trace.

Impedance matching

Making source, line and load impedances equal (Z_s = Z₀ = Z_L) to avoid reflections; done by terminating with resistors and controlled-impedance routing.

Timing skew

The difference in arrival times of a signal (e.g. clock) at different receivers, or between related signals, caused by unequal trace lengths, loads and propagation delays. Reduced by matching trace lengths, balanced loading and clock distribution buffers.

✓ Answer checked by Claude Sonnet 5.5

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