Ring oscillators for high performance clock synthesis and sensor interfaces

Thanks to their small area and multiphase output, ring oscillators (ROs) play important roles in many systems. In this thesis, we study, analyze and propose novel solutions for RO-based applications. We cover three applications for ROs, namely, wireline clock generation, temperature-compensated references, and sensor interfaces. We start by focusing on RO-based clock generation where the phase noise is degraded due to jitter accumulation. We present a synthesizer architecture that uses a low-noise passive multiphase generator which does not suffer from jitter accumulation and digital background calibration to correct for errors in the multiphase generator. The synthesizer uses a standard 54MHz crystal to synthesize a 245fsrms 5GHz output while consuming only 8.2mW. For the frequency reference part, we propose a novel temperature-compensated oscillator (TCO) using a RO locked to RC reference using a frequency locked loop (FLL). High-resolution generated sequences are used to clock switched resistors of opposite temperature coefficients which serve as a reference resistor for the FLL. This results in excellent temperature coefficient of 8.4ppm/◦C from −40◦C to 85◦C while relying on only 2-point trim operation. The TCO also achieves a supply sensitivity of 80ppm/V and power efficiency of 1μW/MHz. For using the RO as a sensor interface, we propose a RO-based temperature sensor where the output period of the RO is locked to an RC sensor using a FLL. We propose a voltage mode FLL structure which guarantees very small area and low noise thanks to a novel 3-phase frequency-to-voltage converter which eliminates charge pump noise. The quantization noise is rejected by passing the 10 phases of the RO to an edge combiner. This allows building a compact temperature sensor occupying 8800μm2 area and achieving ±0.5◦C peak to peak inaccuracy after 1-point trim and 92fJ·K2 resolution FoM.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste