10.7 A 185fsrms integrated jitter and 245dB FOM PVT robust ring VCO based injection locked clock multiplier with a continuous frequency tracking loop using a replica delay cell and a dual edge phase detector
An injection locked clock multiplier (ILCM) is considered to be a promising solution that can generate low jitter, high frequency clocks, using a limited budget in terms of silicon area and power consumption. However, an ILCM has a critical problem in that its jitter performance is sensitive to process, voltage, and temperature (PVT) variations. Thus, in general, an ILCM must be equipped with a dedicated PVT calibrator to mitigate the sensitivity of its performance to PVT variations. One of the most general calibration methods is to use a phase locked loop (PLL) This method can correct static frequency deviations of a voltage controlled oscillator (VCO) due to process variations, but it cannot prevent real time frequency drifts due to temperature or voltage variations [1] Recently, many efforts have been made to develop new PVT calibrators, capable of continuous frequency tracking [1 6] In [1 3] frequency drifts were monitored by a replica VCO or a delay locked loop (DLL) that used the same delay cells as the main VCO. However, in these architectures, each calibrator must spend the same amount of the power as the VCO. In addition, mismatches between delay cells limit the calibrating precision or demand an additional calibrating step. References [4 6] presented frequency tracking loops (FTLs) based on various methods to detect the phase shifts of VCO outputs when reference pulses are injected. Reference [4] used a time to digital converter (TDC) to detect the phase shifts, but it had large power consumption and silicon area due to the many digital circuits. Although the FTL of [5] used a timing adjusted phase detector (PD) it could suffer from large in band noise or spurs since the switches of the charge pump (CP) must be on for a considerable duration in every period. In [6] a pulse gating technique that periodically skipped the injection was presented, but it could generate fractional spurs.
2016 IEEE International Solid State Circuits Conference (ISSCC)