Design consideration of a static memory cell

Describes design criteria for high-density low-power static RAM cells with a four-transistor two-resistor configuration. The states of the cell latch are expressed by a DC stability factor introduced from transfer curves of the inverters in the cell. The criteria use only static conditions for read/write/retain operations. The designed cell, considering mask-misalignment, measured 22.8×27.6 μm with 2.5 μm layout rules. From the evaluation of dynamic characteristics, it was shown that the 16K RAM using the cell had a sufficient operating margin.