A high linear voltage-to-time converter (VTC) with 1.2 V input range for time-domain analog-to-digital converters

Abstract This paper presents a high linear voltage-to-time converter (VTC) with wide input range of over 1.2 Vp-p, diff for the high-speed high-linear time-domain (TD) analog-to-digital converters (ADC). Different from the conventional VTC, the proposed VTC samples the input as the initial charge voltage, and apply current source independent of the input for charge process. Thanks to the high-linear sample and hold (S/H) circuit and low-mismatch current source, the input range and linearity of the proposed VTC are greatly improved. Also, a low propagation-delay comparator is designed for high-speed VTC. The VTC is fabricated in 65 nm CMOS process, occupying an area of 0.012 mm2, consuming power of 0.48 mW. The measured results show that conversion gain of the VTC is as high as 1.95 ns/V. DNL/INL is suppressed within −0.32–0.38 LSB and −0.5–0.6 LSB, respectively. In 250 MHz full Nyquist frequency, SFDR is measured over 66 dB.

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