On-chip measurement of the jitter transfer function of charge-pump phase-locked loops

An all-digital technique for the measurement of the jitter transfer function of charge-pump phase-locked loops is introduced. Input jitter may be generated using one of two methods. Both rely on delta-sigma modulation to shape the unavoidable quantization noise to high frequencies. This noise is filtered by the lowpass characteristic of the device and has a minimal impact on the test results. For response measurement, the output jitter is compared against a threshold. As the stimulus generation and output analysis circuits are digital and do not require calibration, this jitter transfer function measurement scheme is highly amenable to built-in self-test. The technique can also be used to adaptively tune a PLL after fabrication. The validity of the scheme was verified experimentally with off-the-shelf components.