A nonlinearity-corrected CMOS time digitizer IC with 20 ps single-shot precision

This paper describes the effect of the interpolator nonlinearity to the single-shot precision of a time digitizer and presents a method in which a look-up table (LUT) containing the measured integral nonlinearity (INL) of the interpolators is used as a correcting vector to improve the single-shot precision. The method was tested with a CMOS time digitizer IC with 496 /spl mu/s range, 29.59 ps LSB resolution and 28 ps RMS single-shot precision. The worst-case single-shot precision of 35 ps caused by the integral nonlinearity of the interpolators was reduced to /spl les/20 ps in the whole temperature range of -40/spl deg/C to +60/spl deg/C by using a single calibration LUT, which contains the measured INLs of the interpolators at room temperature.