Abstract

In this paper, a sense-amplifier-based flip-flop (SAFF) suitable for low-power high-speed operation is proposed. With the employment of a new sense-amplifier stage as well as a new single-ended latch stage, the power and delay of the flip-flop is greatly reduced. A conditional cut-off strategy is applied to the latch to achieve glitch-free and contention-free operation. Furthermore, the proposed SAFF can provide low voltage operation by adopting MTCMOS optimization. Post-layout simulation results based on a SMIC 55 nm MTCMOS show that the proposed SAFF achieves a 41.3% reduction in the CK-to-Q delay and a 36.99% reduction in power (25% input data toggle rate) compared with the conventional SAFF. Additionally, the delay and the power are smaller than those of the master-slave flip-flop (MSFF). The power-delay-product of the proposed SAFF shows 2.7× and 3.55× improvements compared with the conventional SAFF and MSFF, respectively. The area of the proposed flip-flop is 8.12 μm2 (5.8 μm × 1.4 μm), similar to that of the conventional SAFF. With the employment of MTCMOS optimization, the proposed SAFF could provide robust operation even at supply voltages as low as 0.4 V.

Highlights

  • High speed and low power is the theme of digital circuits

  • In order to verify the validity of the proposed sense-amplifier-based flip-flop (SAFF), the master–slave flip-flop (MSFF), the conventional SAFF, Nikolic’s SAFF, Lin’s SAFF and

  • Hspice with the same settings is adopted to perform all post-layout simulations for comparisons. The performance comparisons such as of the area, power consumption, CK-to-Q delay, setup time and hold time of the various flip-flops are described in detail below

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Summary

Introduction

High speed and low power is the theme of digital circuits. As basic storage elements, the delay and power of the flip-flops directly determines the performance and power of digital systems. The sense-amplifier-based flip-flop (SAFF), first appearing in [7], is another fast flip-flop with a near-zero or negative setup time. With a near-zero or negative setup time and a reduced hold time, the SAFF is a good candidate to substitute MSFF in the standard cell library for high-speed design. Even though these features are attractive, the SAFF has several problems. The pre-charge operation of the SAFF will increase power consumption, and a fast latch structure is needed to reduce the CK-to-Q delay.

Overview of Existing SAFF Architectures
Structure of the Proposed SAFF
Simulation Results and Comparisons
Conclusions

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