An MOS Current Mode Logic (MCML) Circuit for Low-Power Sub-GHz Processors

Hachiro YAMADA

IEICE TRANSACTIONS on Electronics   Vol.E75-C    No.10    pp.1181-1187
Publication Date: 1992/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microprocessors)
Category: Low-Voltage Operation
current mode logic,  low power,  high speed,  MOS,  

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This paper describes a new 0.5-µm MOS current mode Logic (MCML) circuit that operates at 1.2 V, while maintaining high-speed performance, comparable with that of bipolar current mode circuits. An MCML circuit consists of differentially operating MOS transistors and a constant current source. Its performance at low voltage is compared with that of a CMOS circuit and bipolar current mode circuits. At 1.2 V, the MCML circuit has 90% the delay time of a CMOS circuit at 3.3 V. Delay times of CML and ECL circuits are 80% and 67% of that of the MCML circuit, respectively. Power of a 0.5-µm 500-MHz MCML circuit at 1.2 V, however, is 29%, 67% and 46%, of that of CMOS at 3.3 V, CML at 1.8 V and ECL at 2.6 V, respectively. Power-delay products of 500-MHz CMOS, CML and ECL circuits (normalized by the MCML circuit power-delay product) are 3.8, 1.2 and 1.5, respectively. MCML circuits can be used to construct any logic circuits. High-speed compact circuits are feasible, because MCML circuits output complementary signals. The delay time of an MCML full adder is only 200 ps. This is three times faster than that of a 3.3-V CMOS full adder. An MCML circuit has good characteristics and is widely applicable to logic circuits, so it is a useful circuit for producing sub-GHz processors.