This paper 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 feature using 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.
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