Contamination delay

Contamination delay

In digital circuits, the contamination delay is the minimum amount of time needed for the output of an electronic component's output to match input presented to it(i.e. contamination delay = hold time + device internal I/O propagation time). If there is insufficient delay from the output of one flip-flop to the input of the next, the input may change before the hold time has passed. Because the second flip-flop is still unstable, its data would then be "contaminated." Every path from an input to an output can be characterized with a particular contamination delay.

Well-balanced circuits will have similar speeds for all paths through a combinational stage, so the minimum propagation time is close to the maximum. This corresponding maximum time is the propagation delay. The condition of data being contaminated is called a race.

References: 1. http://www.nileshgoel.com/wp-content/uploads/2010/02/timing-note.pdf