A CMOS pulse-shrinking delay element for time interval measurement

A deep sub-nanosecond resolved CMOS pulse-shrinking delay element used in the time-to-digital converter (TDC) is proposed. The pulse shrinking capability of the element is controlled by the dimension ratio of the adjacent gates. This control mechanism is completely different from the bias adjustment adopted in the conventional pulse-shrinking element. Without the need of continuous calibration, the presented element possesses not only extremely fine resolution, small single-shot errors, low power consumption, but also good insensitivity to the supply voltage variation. Being fabricated with 0.35 μm CMOS technologies, the TDC made of the new elements has been measured to have a resolution of 68 ps. The effective resolution only varies 1.5 ps for a rather large supply voltage range from 3.5 to 4.5 V. The size of the circuit is 0.35 mm×0.09 mm only, excluding the I/O pads. Under a single 3.3-V power supply, the static power dissipation, including the I/O pads, is 1 μW. The average power consumption is measured to be merely 1.2 mW under a measurement rate of 100 ksps