Self-calibration of digital phase-locked loops

A novel method for the measurement of the jitter transfer function of digital phase-locked loops is presented. The signal generation and analysis circuits are entirely digital except for an extra charge-pump. They hence do not require calibration. Contrary to other phase-locked loop digital measurement schemes, a clock frequency larger than the phase-locked loop operating frequency is not necessary. Because the area overhead is small, our scheme is highly amenable to on-chip tuning of analog components for compliance to specifications. This method could also be used to implement built-in self-test for phase-locked loops. Experiments with discrete components show the jitter transfer function measuring method is sound.