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

• Published in: ESSCIRC 2023- IEEE 49th European Solid State Circuits Conference (ESSCIRC) pp. 273 - 276
• Main Authors: Shin, Jiwon, Song, Joonghyun, Kim, Jihee, Choi, Woo-Seok
• Format: Conference Proceeding
• Language: English
• Published: IEEE 11.09.2023
• Subjects: CMOS process; Delays; Detectors; error-tracking technique; Injection-locked clock multiplier (ILCM); Jitter; Low voltage; nearthreshold operation; Phase noise; Prototypes; spur reduction
• ISSN: 2643-1319
• DOI: 10.1109/ESSCIRC59616.2023.10268709

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.