Abstract
An integrated circuit that measures time intervals with high precision and accuracy has a wide range of applications including data conversion, ranging, and 3-D imaging. The resolution with which time intervals are quantized by a ring oscillator or delay line is limited by the minimum delay of an inverter in the technology. We propose the use of cyclic-coupled ring oscillators (CCROs) as a time-domain quantizer to achieve a combination of subgate-delay time resolution together with a short conversion time, thereby enabling data conversion with high resolution as well as high bandwidth. The resolution-power tradeoff in coupled oscillators is studied. Simulation indicates up to a factor-of-13 subgate-delay time resolution with 13 coupled oscillators. A real-time quantizing time-to-digital converter with coupled oscillators is designed for a time-domain analog-to-digital converter. Powered by a factor-of-8 subgate-delay time resolution of 1.6 ps obtained with nine coupled oscillators, and a sample time of 4 ns for 11-bit conversion, the converter delivers a 9.9-bit ENOB over a signal bandwidth of 125 MHz and an SFDR of 88 dB. Results demonstrate that CCROs is an attractive candidate as a high-precision high-linearity time-domain quantizer for data converters.
Original language | English |
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Pages (from-to) | 203-214 |
Journal | IEEE Transactions on Very Large Scale Integration (VLSI) Systems |
Volume | 29 |
Issue number | 1 |
DOIs | |
Publication status | Published - Jan 2021 |
Externally published | Yes |
Publication type | A1 Journal article-refereed |