A 2T1C Embedded DRAM Macro With No Boosted Supplies Featuring a 7T SRAM Based Repair and a Cell Storage Monitor

Abstract

A truly logic-compatible gain cell eDRAM macro with no boosted supplies is presented. A 2T1C gain cell implemented only with regular thin oxide devices consists of an asymmetric 2T cell and a coupling PMOS capacitor. The PMOS capacitor ensures proper operation even without a boosted supply by utilizing a beneficial coupling for read and a preferential boosting for write. A repair scheme based on a single-ended 7T SRAM has features such as a local differential write and shared control with the main 2T1C array. A storage voltage monitor is proposed to track the retention characteristics of a gain cell eDRAM under PVT variations and to adjust its refresh rate adaptively. A 128 kb eDRAM test chip implemented in a 65 nm Low-Power (LP) process operates at a random access frequency of 714 MHz with a static power dissipation of 161.8 μW per Mb for a 500 μs refresh rate at 1.1 V and 85°C.