Abstract
This paper presents subthreshold digital circuit design and optimization method using Schmitt trigger logic gates for enhanced electromagnetic immunity. The proposed Schmitt trigger logic gates are based on a buffer design using dynamic thresholdvoltage MOS for low-power operation. By expanding the Schmitt trigger to NAND/NOR gate, we can dramatically improve the noise immunity with much lower switching power consumption and significant area reduction compared with CMOS Schmitt triggers, at the expense of a slight increase in delay. Not only for the gate level, but also the circuit level immunity improvement is verified with ISCAS 85 benchmark. In addition, we propose a parameter to determine the optimal noise immunity considering the tradeoff between immunity and performance. By using the proposed parameter, optimal hysteresis can be chosen for the reasonable performance deterioration.
