A High-Accuracy and Fast-Correction Quadrature Signal Corrector Using an Adaptive Delay Gain Controller for Memory Interfaces

Abstract

In this paper, a quadrature signal corrector (QSC) with high accuracy and fast correction for memory interfaces is presented. An adaptive delay gain controller in the QSC adjusts each delay gain of four digitally controlled delay lines (DCDLs) separately depending on skew between the quadrature clocks, resulting in short correction time together with low residual skew. To validate the effectiveness of our QSC in memory interfaces, a quarter-rate single-ended 1-tap decision feedback equalizer (DFE) with the QSC was fabricated in a 65nm CMOS process. Using the adaptive delay gain controller, the QSC reduced the skew between the 3 GHz quadrature clocks from a maximum of 21.2 ps to 0.8 ps while correction time was reduced by a factor of 3.9 compared to that without using the adaptive delay gain controller. At 12 Gb/s, the DFE using our QSC achieved a BER of 10 −12 with an eye width of 140 mUI when the input clock skew is 13.2 ps.