A Wide Range, 4.2 ps(rms) Precision CMOS TDC With Cyclic Interpolators Based on Switched-Frequency Ring Oscillators.

A time-to-digital (TDC) converter based on cyclic interpolators has been designed. The TDC is designed to be used in a pulsed time-of-flight laser radar, where a long measurement range is required. The TDC's two interpolators provide a picosecond level resolution, which is combined with a main reference clock counter to give a measurement range of 327 \mus. The interpolators measure time intervals with a switched-frequency ring oscillator. The frequency switching is used as a mechanism to amplify the quantization error in the cyclic interpolator. A digital calibration scheme is used for radix extraction. The interpolators' worst case INL is \pm4.5 ps. Due to the interpolator's INL, the TDC's RMS precision is about 4.2 ps, while the worst and best case single-shot precisions are 5.5 ps and 1.7 ps, respectively. The overall accuracy of the TDC is better than 5 ps in a temperature range of -30 C to 70 C. The TDC is designed in 0.35 \mum CMOS technology and consumes 80 mW at 0.8 MHz measurement rate. [ABSTRACT FROM AUTHOR]