US Patent 7173468 Multiple-input, single-exit delay line architecture

A delay line includes a delay chain consisting of series-connected NAND gate delay stages with a delayed output signal extracted from the final delay stage. Tap decode gates are preferably used to “inject” the input signal to be delayed into the delay chain using one input of the NAND gate delay stage, referred to as an “injection point.” The desired delay is achieved by selecting an injection point relative to the final delay stage, or exit point, of the delay chain. Selection of an injection point is provided by the binary decode of a tap address that activates the injection NAND gate delay stage, allowing the injected signal to propagate from the activated injection point to the exit point of the delay chain.