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A Low Power High-Speed 8-Bit Pipelining CLA Design Using Dual-Threshold Voltage Domino Logic

Chua-Chin Wang, Chi-Chun Huang, Ching-Li Lee, and Tsai-Wen Cheng

Very Large Scale Integration (VLSI) Systems, IEEE Transactions on Volume 16, May 2008, Page(s):594 - 598

Adviser : Kai-Cheng Wei

Postgraduate : Chiuan-Tai Xiao

Number : 96662011

Date : 2008.11.24

National Changhua University of Education

Graduate Institute of Integrated Circuit Design

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Outline

Abstract

Low-power high-speed 8-bit CLA

Simulations and implementation

Conclusion

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Abstract A high speed and low power 8-bit carry-lookahead adder using t

wo-phase modified dual-Vt domino logic blocks which are arranged in a PLA-like design style with pipelining is presented.

The modified domino logic circuits employ dual-Vt transistors and reversed bulk-source biases for reducing subthreshold leakage current when advanced deep submicrometer process is used.

The proposed dynamic power consumption is also drastically reduced by more than 10% by the measurement results on silicon.

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Low-power high-speed 8-bit CLA

a. Typical dual-Vt domino logic circuits

precharge phase

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evaluation phase

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Typical two-stage dual-Vt domino logic circuit to construct a pipeline structure

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b. Modified dual-Vt domino logic circuits

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c. High-Vt transistor with reverse-biased bulk-source voltage

In the simulation, Vdd=1.8V, VB=3V, T=25 C.

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d. PLA-styled 8-bit CLA design(1)

Ci+1 = Gi + Pi ● Ci

Gi=Ai ● Bi

Pi = Ai xor Bi

NOT-OR plane

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d. PLA-styled 8-bit CLA design(2)

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e. Cycle-based operation and area analysis

An 8-bit adder using our proposed design, the overalltransistor count is 882.

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Simulations and implementation(1)

To reveal the power-saving advantage of the proposed low power design, two 8-bit CLAs are, respectively, implemented by the modified single-Vt domino logic and the modified dual-Vt domino logic using the same CMOS process.

The two CLAs implemented by TSMC 0.18-µm 1P6M CMOS process.

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Simulations and implementation(2)

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Simulations and implementation(3)

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Simulations and implementation(4)

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Conclusion

We propose a low-power high-speed PLA-styled dual-Vt domino logic design for adder implementation.

A modified dual-Vt domino logic circuit is used for pipelining structure and the unnecessary power consumption is avoided.

Not only is the correctness of the function in the gigahertz range preserved, the power dissipation is also reduced.

The PLA-styled dual-Vt domino logic structure using only one clock makes the result of an 8-bit adder appear in two cycles.

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Thanks for your attention.