Low-cost jitter measurement technique for phase-locked loops

A new low-cost technique for jitter measurement of phase-locked loops (PLLs) is described. The proposed technique can be applied to PLLs whose jitter is predominantly due to power supply noise. Accurate measurement of jitter to picosecond accuracy using conventional methods requires very high-cost tester instrumentation. By modulating the supply voltage to the PLL and noting that PLL jitter is extremely sensitive to power supply variations, it is possible to introduce significant jitter into the PLL output which can be measured using a low-cost tester During production test, a regression model is used to predict the inherent PLL jitter from the measurement of power supply induced jitter.