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

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 $0.0097\mathrm{m}\mathrm{m}^{2}.$ It generates output clocks of lGHz and 300MHz, operating at supply voltages of 0.5 V and 0.4V, respectively. The integrated jitter is $2.50\mathrm{p}\mathrm{s}_{\mathrm{R}\mathrm{M}\mathrm{S}}$ and $10.7\mathrm{p}\mathrm{s}_{\mathrm{R}\mathrm{M}\mathrm{S}}$ for each voltage, and the reference spur is recorded at -64.0dBc and -64.5dBc, while achieving an FoM of -239dB and -232dB.