An optical clock receiver based on an injection locked ring oscillator featuring auto-calibration

Abstract

An auto-calibration technique for injection locked ring oscillators (ILO) used as clock receivers is presented. ILOs have various clock distribution applications but need continuous active calibration, due to their sensitivity to PVT variations. The proposed circuit is capable of tracking environmental variations, due to aging or temperatuer variations, while keeping the lock to the injected signal. In particular this circuit has an acquisition range of 2.25 to 3.0 GHz, which allows locking the system to 2.5 GHz for temperature variations between 0C and 80C even for SS and FF corner variations, with injected currents of 5 µA of amplitude and duty cycle of 10%. The circuit was designed and tested in a fully-depleted SOI CMOS 28nm technology. It consumes 500 µA with active calibration and only 60 µA with deactived calibration.