Asymmetric Slope Dual Mode Differential Logic Circuit for Compatibility of Low-Power and High-Speed Operations

Masao MORIMOTO
Makoto NAGATA
Kazuo TAKI

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.4    pp.675-682
Publication Date: 2007/04/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.4.675
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Low-Power, High-Speed LSIs and Related Technologies)
Category: Digital
Keyword: 
ASDMDL,  differential logic,  high-speed logic,  low-power logic,  

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Summary: 
Asymmetric Slope Dual Mode Differential Logic (ASDMDL) embodies high-speed dynamic and low-power static operations in a single design. Two-phase dual-rail logic signaling is used in a high-speed operation, where a logical evaluation is preceded by pre-charge, and it asserts one of the rails with an asymmetrically shortened rise transition to express a binary result. On the other hand, single-phase differential logic signaling eliminates pre-charge and leads to a low-power static operation. The operation mode is defined by the logic signaling styles, and no control signal is needed in the logic cell. The design of mixed CMOS and ASDMDL logic circuits can be automated with general logic synthesis and place-and-route techniques, since the physical ASDMDL cell is prepared in such a way to comply with a CMOS standard-cell design flow. A mixed ASDMDL/CMOS micro-processor in a 0.18-µm CMOS technology demonstrated 232 MHz operation, corresponding to 14% speed improvement over a full CMOS implementation. This was achieved by substituting ASDMDL cells for only 4% of the CMOS logic cells in data paths. The low-speed operation of ASDMDL at 100 MHz was nearly equivalent to that of CMOS. However, power consumption was reduced by 3% due to the use of ASDMDL complex logic cells. Area overhead was less than 4%.