Pseudo Multi-Port SRAM Circuit for Image Processing in Display Drivers

Abstract

N×N filter operations are frequently used in various image processing algorithms in display driver circuits. The implementation of the N×N filter requires a storage element to temporarily retain N or N-1 lines of display data. The traditional approach for this temporary storage element for N×N image filter is either by using N blocks of memory to store N lines of display data with single-port six-transistor (6T) SRAM bit-cells or by using N-1 blocks of memory to store N-1 lines of display data with dual-port eight-transistor (8T) SRAM bit-cells. In this paper, a pseudo multi-port SRAM circuit is proposed for N×N filter in image processing in a display driver integrated circuit (IC). By using pre-read mechanism and word-line/column selection signal forwarding technique, the proposed approach only stores N-1 lines of display data and can use the small single-port 6T SRAM bit-cells. For a 3×3 filter application, the proposed approach reduces the overall layout area by 50.3% and 30.2% compared to the traditional dual-port 8T and single-port 6T memory implementations, respectively, in an industrial 0.18- μm CMOS technology. Furthermore, the power used to perform a 3×3 filter operation is reduced by 47% and 30.8% with the proposed approach as compared to the traditional dual-port 8T and signal-port 6T memory circuits, respectively, with slight degradation of the access speed.