A Near-Threshold Ring-Oscillator-Based ILCM with Edge-Selective Error Detector Achieving-64 dBc Reference-Spur and-239 dB FoM

Abstract

A near-threshold ring-oscillator (RO)-based injection-locked clock multiplier (ILCM) with a novel error detection scheme is presented. The proposed ILCM employs a robust calibrator with reduced delay range and low-frequency operation, effectively suppressing the phase noise of the RO despite low-voltage operation. This leads to exceptional jitter performance while occupying a minimal area. Moreover, by eliminating the pulse distortion impact from the frequency detector, precise frequency tracking is achieved and deterministic jitter is effectively suppressed. The prototype ILCM is fabricated in a 28nm CMOS process with an active area of 0.0097mm(2). It generates output clocks of 1GHz and 300 MHz, operating at supply voltages of 0.5V and 0.4V, respectively. The integrated jitter is 2.50 psRMS and 10.7 psRMS for each voltage, and the reference spur is recorded at -64.0 dBc and -64.5 dBc, while achieving an FoM of -239 dB and -232 dB.