Bi-directional Input/Output Circuits with Integrated Level Shifters for Near-threshold Computing

摘要

Interfacing techniques for near-threshold computing are described in this paper. A bi-directional input/output circuit with integrated level shifters is proposed for multiple near-threshold power domains. The circuit provides conversion ranges of 0.38 V to 1.2 V and 0.45 V to 3.3 V depending on the targeted output voltage. Eight different configurations of I/O circuits are evaluated with level shifters implemented with a standard current mirror, cross coupled, and the proposed single ended topology. The use of a single ended level shifter provides the optimum power-delay point. The I/O circuit, at a core voltage of 0.45 V, consumes 4.87 mW with a fanout of four (FO4) delay of 0.46 for a V_(DOUT) and V_(PAD) voltage of, respectively, 0.45 V and 3.3 V. For a V_(DD, L) of 0.625 V and V_(DD, H) of 1.5 V, the delay and total power consumption of the single ended level shifter are, respectively, 0.74× and 0.4× that of a current mirror level shifter.