HIGH SPEED CHIP SCREENING METHOD USING DELAY LOCKED LOOP

摘要

A voltage controlled delay line (VCDL) for measuring the maximum speed of a chip includes a first input configured to receive a reference clock signal, a first output configured to output an output clock signal, and a second input configured to receive a phase error signal representing a phase delay between the reference and output clock signals. A register stores a delay code applied by the VCDL to the reference clock signal to delay the reference clock signal to generate the output clock signal. The delay code is adjusted according to the phase error signal until the phase delay is equal to a predetermined value. A second output is coupled to an interface that reads the delay code from the register and outputs the delay code to automated testing equipment when the phase delay is equal to the predetermined value. The outputted delay code corresponds to the maximum chip speed.