Recently reported logic style comparisons based on full-adder circuits claimed complementary pass-transistor logic (CPL) to be much more power-efficient than complementary CMOS. However, new comparisons performed on more efficient CMOS circuit realizations and a wider range of different logic cells, as well as the use of realistic circuit arrangements demonstrate CMOS to be superior to CPL in most cases with respect to speed, area, power dissipation, and power-delay products. An implemented 32-b adder using complementary CMOS has a power-delay product of less than half that of the CPL version. Robustness with respect to voltage scaling and transistor sizing, as well as generality and ease-of-use, are additional advantages of CMOS logic gates, especially when cell-based design and logic synthesis are targeted. This paper shows that complementary CMOS is the logic style of choice for the implementation of arbitrary combinational circuits if low voltage, low power, and small power-delay products are of concern.

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Low-power logic styles: CMOS versus pass-transistor logic

A 10-bit 40-Msample/s two-channel parallel pipelined ADC with monolithic digital background calibration has been designed and fabricated in a 1 /spl mu/m CMOS technology. Adaptive signal processing and extra resolution in each channel are used to carry out digital background calibration. Test results show that the ADC achieves a signal-to-noise-and-distortion ratio of 55 dB for a 0.8-MHz sinusoidal input, a peak integral nonlinearity of 0.34 LSB, and a peak differential nonlinearity of 0.14 LSB, both at a 10-bit level. The active area is 42 mm/sup 2/, and the power dissipation is 565 mW from a 5 V supply.

A digital background calibration technique for time-interleaved analog-to-digital converters

We present two high-speed and low-power full-adder cells designed with an alternative internal logic structure and pass-transistor logic styles that lead to have a reduced power-delay product (PDP). We carried out a comparison against other full-adders reported as having a low PDP, in terms of speed, power consumption and area. All the full-adders were designed with a 0.18-μm CMOS technology, and were tested using a comprehensive testbench that allowed to measure the current taken from the full-adder inputs, besides the current provided from the power-supply. Post-layout simulations show that the proposed full-adders outperform its counterparts exhibiting an average PDP advantage of 80%, with only 40% of relative area.

CMOS Full-Adders for Energy-Efficient Arithmetic Applications

The pass-transistor based cell library and synthesis tool are constructed, for the first time, to clarify the potential of top-down pass-transistor logic. The entire scheme is called LEAP (Lean Integration with Pass-Transistors). The feature of a pass-transistor based cell is its multiplexer function and the open-drain structure. This cell has the flexibility of transistor level circuit design and compatibility with conventional cell based design. An extremely simple cell library with only seven cells combined with a synthesis tool called "circuit inventor" is compared with the conventional CMOS library that has over 60 cells combined with the state-of-the-art logic synthesis. The results show that the area, delay, and power dissipation are improved by LEAP and that the value-cost ratio is improved by a factor of three. This demonstrates that LEAP has the potential to achieve a quantum leap in value of LSI's while reducing the cost. Key issues which have to be cleared before pass transistor logic is used as the generic logic scheme replacing CMOS are also discussed.

Top-down pass-transistor logic design

In this paper we present circuit techniques for CMOS low-power high-performance multiplier design. Novel full adder circuits were simulated and fabricated using 0.8-/spl mu/m CMOS (in BiCMOS) technology. The complementary pass-transistor logic-transmission gate (CPL-TG) full adder implementation provided an energy savings of 50% compared to the conventional CMOS full adder. CPL implementation of the Booth encoder provided 30% power savings at 15% speed improvement compared to the static CMOS implementation. Although the circuits were optimized for (16/spl times/16)-b multiplier using the Booth algorithm, a (6/spl times/6)-b implementation was used as a test vehicle in order to reduce simulation time. For the (6/spl times/6)-b case, implementation based on CPL-TG resulted in 18% power savings and 30% speed improvement over conventional CMOS.

Circuit techniques for CMOS low-power high-performance multipliers

Describes circuit techniques for fabricating a high-speed adder using pass-transistor logic. Double pass-transistor logic (DPL) is shown to improve circuit performance at reduced supply voltage. Its symmetrical arrangement and double-transmission characteristics improve the gate speed without increasing the input capacitance. A carry propagation circuit technique called conditional carry selection (CCS) is shown to resolve the problem of series-connected pass transistors in the carry propagation path. By combining these techniques, the addition time of a 32-b ALU can be reduced by 30% from that of an ordinary CMOS ALU. A 32-b ALU test chip is fabricated in 0.25- mu m CMOS technology using these circuit techniques and is capable of an addition time of 1.5 ns at a supply voltage of 2.5 V. >

A 1.5-ns 32-b CMOS ALU in double pass-transistor logic

A 54/spl times/54-b multiplier using pass-transistor multiplexers has been fabricated by 0.25 /spl mu/m CMOS technology. To enhance the speed performance, a new 4-2 compressor and a carry lookahead adder (CLA), both featuring pass-transistor multiplexers, have been developed. The new circuits have a speed advantage over conventional CMOS circuits because the number of critical-path gate stages is minimized due to the high logic functionality of pass-transistor multiplexers. The active size of the 54/spl times/54-b multiplier is 3.77/spl times/3.41 mm. The multiplication time is 4.4 ns at a 3.5-V power supply. >

A 4.4 ns CMOS 54/spl times/54-b multiplier using pass-transistor multiplexer

A 54/spl times/54-b multiplier using pass-transistor multiplexer has been fabricated by 0.25-/spl mu/m CMOS technology. To enhance the speed performance, a new 4-2 compressor and a carry look-ahead adder (CLA) both featuring the use of pass-transistor multiplexers have been developed. The new circuits have a speed advantage over conventional CMOS circuits because the number of critical-path gate stages is minimized due to the high logic functionality of pass-transistor multiplexers. The active size of the 54/spl times/54-b multiplier is 3.77 mm/spl times/3.41 mm. The multiplication time is 4.4 ns at 2.5 V power supply. >

http://ieeexplore.ieee.org/iel2/3036/8629/00379651.pdf

T. Shinbo

Papers

A 1.5-ns 32-b CMOS ALU in double pass-transistor logic

A 4.4 ns CMOS 54/spl times/54-b multiplier using pass-transistor multiplexer

A 4.4-ns CMOS 54/spl times/54-b multiplier using pass-transistor multiplexer