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Issue #210 January 2008
Problem 3—What is ground bounce, and what causes it?
Answer 3: Ground bounce is a momentary difference in voltage (usually positive) between “ground” on the surface of an integrated circuit and “ground” on the PCB to which it is attached. It is caused by pulses of current in the ground pin(s) interacting with the nonzero impedance of the bonding wire, pin and PCB trace.
The single most common source of such current pulses is an output pin on the chip switching from high to low, as the pull-down transistor on the pin dumps the charge on the output line to ground. It is exacerbated by having multiple such pins (e.g., a data bus) switching at the same time.
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