Equal-slope baud-rate CDR algorithm with optimized eye opening

Abstract

A novel equal-slope baud rate clock and data recovery (CDR) algorithm is proposed. By positioning the locked point on pulse response where pre-cursor slope and main-cursor slope are equal, an optimized eye-opening is achieved with enhanced eye height, eye width and timing margin. The algorithm is realized in high-speed wireline receiver by finding the sampling position with maximum probability over an adaptive reference voltage when adjacent two data are opposite, with a double transition density over conventional Mueller-Muller (MM) algorithm. With no need for extra power-consuming or timing-critical circuits, this algorithm is readily integrated into prevalent decision feedback equalization (DFE). Simulation shows more than 18.0%, 14.4% and 56.1% improvement in recovered eye height, eye width and time margin, respectively, over its MM counterpart with >10 ​dB channel loss@14 ​GHz. Clear eye improvement could also be seen with respect to classical bang-bang CDR. Moreover, equal-slope CDR demonstrates significant locked point stability against system noise thanks to alienation from nearly-flat region.