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.
|Number of pages||12|
|Journal||IEEE Transactions on Very Large Scale Integration (VLSI) Systems|
|Publication status||Published - Jan 2021|
|MoE publication type||A1 Journal article-refereed|
- Analog-to-digital converter (ADC)
- cyclic coupled ring oscillator (CCRO)
- data converter
- ring oscillator
- time resolution
- time-of-flight (ToF)
- time-to-digital converter (TDC)
- ToF sensor
- VCO-based ADC.