In-pixel voltage-controlled ring-oscillator for phase interpolation in ToF image sensors

• Published in: 2016 IEEE International Symposium on Circuits and Systems (ISCAS) pp. 1906 - 1909
• Main Authors: Vornicu, I., Carmona-Galan, R., Rodriguez-Vazquez, A.
• Format: Conference Proceeding Journal Article
• Language: English
• Published: IEEE 01.05.2016
• Subjects: Arrays; CMOS; Design engineering; Frequency conversion; Frequency measurement; Gain; Interpolation; Occupation; Offsets; Oscillators; phase interpolator; Phase locked loops; Power demand; pseudo-differential voltage-controlled ring-oscillator; time-to-digital converter; Tuning; Voltage control; Voltage measurement
• ISSN: 2379-447X
• DOI: 10.1109/ISCAS.2016.7538945

The design and measurements of a CMOS pseudodifferential voltage-controlled ring-oscillator (VCRO) are presented. It is aimed to act as time interpolator for arrayable picosecond time-to-digital convertors (TDC). This design is incorporated into a 64×64 array of TDCs for time-of-flight (ToF) measurement. It has been fabricated in a 0.18μ™ standard CMOS technology. Small occupation area of 28×29μm2 and low average power consumption of 1.17mW at 850MHz are promising figures for this application field. Embedded phase alignment and instantaneous start-up time are required to minimize the offset of time interval measurements. The measured gain of the VCRO is of 477MHz/V with a frequency tuning range of 53%. Moreover it features a linearity of 99.4% over a wide range of control frequencies, namely from 400MHz to 850MHz. The phase noise is of 102dBc/Hz at 2MHz offset frequency from 850MHz.