A 28nm 36kb High Speed 6T SRAM with Source Follower PMOS Read and Bit-Line Under-Drive

Abstract

In this paper, we present source follower PMOS Read and bit-line under-drive techniques to improve the operation speed as compared to present commercial SRAM compilers. A source follower PMOS is utilized to connect local bit-lines (LBL) to global bit-lines (GBL) instead of using a NAND gate. To further improve the discharging time from LBL to GBL, we propose a bit-line under-drive circuit to reduce the voltage level of LBL. The simulated access time of the proposed macro is 445 ps at slow N slow P (SS) corner, -40 degrees C, 0.81 V. As compared to the SRAM macro which is generated by commercial SRAM compilers with the fastest combination, the access time of the proposed SRAM macro is 12% faster than that of commercial SRAM compilers. A 36kb high speed 6T SRAM macros with source follower PMOS Read and bit-line under-drive techniques is fabricated in 28nm HKMG CMOS process. The measurement results of the chip in SS corner show the proposed SRAM macro passes all MBIST patterns at 500 MHz at 0.81 V, room temperature.