SRAM cell with independent static noise margin, trip voltage, and read current optimization

摘要

An SRAM memory cell structure utilizing a read driver transistor for isolating the read current from the latch nodes of the cell during read operations and a column select write transistor for selection of a single cell during write operations, and a method of operating the same is discussed. The SRAM memory cell structure (single-ended or differential cell) allows independent optimization of the static noise margin, trip voltage, and read current, thereby avoiding some of the static noise margin and trip voltage problems of conventional SRAM cells (e.g., a conventional 6T differential cell). In one implementation, the SRAM memory cell comprises a 7T single-ended cell including first and second cross-coupled inverters, having a first and second latch nodes, respectively. The cell further comprises a first write pass transistor connected between the first latch node of the first inverter and a first pass node, and a first wordline pass transistor connected between the first pass node and a first bitline. The cell also includes a first read driver connected between the first pass node and a source potential, and a control terminal of the first read driver connected to the second latch node of the second inverter. Beneficially, the read current conducts through the first read driver to avoid upsetting the data state at the latch node. Further, a differential 10T SRAM memory cell for coupling to a complimentary pair of bitlines is discussed, having all the elements mentioned above used in the exemplary 7T cell.