Conditional-capture flip-flop for statistical power reduction

This paper describes a family of novel low-power flip-flops, collectively called conditional-capture flip-flops (CCFFs). They achieve statistical power reduction by eliminating redundant transitions of internal nodes. These flip-flops also have negative setup time and thus provide small data-to-output latency and attribute of soft-clock edge for overcoming clock skew-related cycle time loss. The simulation comparison indicates that the proposed differential flip-flop achieves power savings of up to 61% with no impact on latency while the single-ended structure provides the maximum power savings of around 67%, as compared to conventional flip-flops. With a typical switching activity of 0.33, the power consumption is reduced by as much as 23-30% with comparable minimum data-to-output latency. It is also indicated that the proposed single-ended structure provides power comparable to the fully static master-slave design with significantly reduced data-to-output latency. An eight-bit counter was fabricated using a 0.35-μm CMOS technology, and the experimental results indicate that the counter using the differential CCFF saves the overall power consumption by about 30% as compared to that using the conventional flip-flop     

High-performance and low-power conditional discharge flip-flop

In this paper, high-performance flip-flops are analyzed and classified into two categories: the conditional precharge and the conditional capture technologies. This classification is based on how to prevent or reduce the redundant internal switching activities. A new flip-flop is introduced: the conditional discharge flip-flop (CDFF). It is based on a new technology, known as the conditional discharge technology. This CDFF not only reduces the internal switching activities, but also generates less glitches at the output, while maintaining the negative setup time and small D-to-Q delay characteristics. With a data-switching activity of 37.5%, the proposed flip-flop can save up to 39% of the energy with the same speed as that for the fastest pulsed flip-flops.     

Low clock-swing conditional-precharge flip-flop for more than 30%power reduction

A low clock-swing flip-flop based on a conditional precharge scheme is proposed to save both clock system power and supply power. Unlike previous reduced clock-swing flip-flops, the new flip-flop will not precharge and discharge when the input data do not change. Compared with previous low clock-swing flip-flops, the new flip-flop leads to savings of at least 30% of the total power     

A New Family of Sequential Elements With Built-in Soft Error Tolerance for Dual-VDD Systems

In this paper, we propose some soft-error-tolerant latches and flip-flops that can be used in dual-VDD systems. By utilizing local redundancy and inner feedback techniques, the latches and flip-flops can recover from soft errors caused by cosmic rays and particle strikes. The proposed flip-flop can be used as a level shifter without the problems of static leakage and redundant switching activity. Implemented in a standard 0.18- $mu{hbox{m}}$ technology, the proposed latches and flip-flops show superior performance compared to conventional ones in terms of delay and power while keeping the soft-error-tolerant characteristic. Experimental results show that compared to the traditional built-in soft-error-tolerant D latch, the D-QN delay of the new D latch is 29.1% less than that of the traditional built-in soft-error-tolerant D latch while consuming 16.5% less power as well. The D-Q delay and power of the new flip-flop are about 47.7% and 54% less than those of the traditional high speed level-converting flip-flop, respectively. In addition, the proposed flip-flop is more robust to soft errors. The critical charge which represents the minimum charge at the D input required to cause an error of the flip-flop can be increased by more than 46.4%. The time window during which the flip-flop will be erroneous caused by single-event upsets at the D input is reduced by more than 22.2%.      

Low-Power Clock Branch Sharing Double-Edge Triggered Flip-Flop

In this paper, a new technique for implementing low-energy double-edge triggered flip-flops is introduced. The new technique employs a clock branch-sharing scheme to reduce the number of clocked transistors in the design. The newly proposed design also employs conditional discharge and split-path techniques to further reduce switching activity and short-circuit currents, respectively. As compared to the other state of the art double-edge triggered flip-flop designs, the newly proposed CBS_ip design has an improvement of up to 20% and 12.4% in view of power consumption and PDP, respectively     

Loosely coupled multi-bit flip-flop allocation for power reduction

Merging 1-bit flip-flops into multi-bit flip-flops in the post-placement stage is one of the most effective techniques for minimizing clock power. In this work, we introduce a new style of multi-bit flip-flop, called loosely coupled multi-bit flip-flop (LC-MBFF). The merit of LC-MBFF is that the logically constituent 1-bit flip-flops in LC-MBFF can be physically apart (i.e., no relocation), providing no need to set aside white space. Utilizing LC-MBFFs, we propose a multi-bit flip-flop allocation algorithm which fully explores the diverse allocation of LC-MBFF structures to maximally reduce clock power consumption. Experimental results with ISCAS89 and IWLS2005 benchmark circuits show that our proposed allocation algorithm using the newly designed multi-bit flip-flops is able to reduce on average the clock power by 8.51% while the best known multi-bit flip-flop allocation algorithm [7] reduces by 5.37%. Additionally, we extend our algorithm to support the multi-bit flip-flop allocation for circuits with clock polarity assignment.     

Low-power level converting flip-flop with a conditional clock technique in dual supply systems

Clustered voltage scaling (CVS) is an effective way to reduce power consumption in digital integrated circuits. Level-converting flip-flops are the critical elements in the CVS scheme. In this paper a single edge implicit pulse-triggered level-converting flip-flop with a conditional clock technique (CC-LCFF) is proposed and proved to be suitable for use in low-power non-critical paths with Dual-VDD. CC-LCFF conditionally blocks the clock signal when the input data does not make any transition, so the redundant transitions of internal nodes are eliminated and the total power consumption is reduced. Based on the SMIC 65 nm technology, the post-layout simulation results show that the proposed CC-LCFF shows an improvement of 69.41–72.40% in power consumption and 23.36–47.73% in power-delay product (PDP) as compared with its counterparts.     

能量回收技术在D触发器上的应用

将能量回收技术应用于灵敏放大器型D触发器(SAERD),该电路采用单相正弦时钟,用来回收时钟端的能量,对于触发器的内部节点和存储单元仍采用恒定电源。在时钟频率为100～300MHz时,时钟端的功耗较输入方波时平均节省约80%。在SMIC0.13μm工艺下将SAERD应用于一款函数发生器,并与传统主从型D触发器(MSD)实现的电路进行功耗比较。仿真结果显示,时钟频率为200MHz时,功耗节省高达17.1%。     

Low power flip-flop with clock gating on master and slave latches

A new flip-flop is presented in which power dissipation is reduced by deactivating the clock signal on both the master and slave latches when there are no data transitions. The new circuit overcomes the clock duty-cycle constraints of previously proposed gated flip-flops. The power consumption of the presented circuit is significantly lower than that of a conventional flip-flop when the D input has a reduced switching activity     

A low-swing clock double-edge triggered flip-flop

A low-swing clock double-edge triggered flip-flop (LSDFF) is developed to reduce power consumption significantly compared to conventional flip-flops. The LSDFF avoids unnecessary internal node transitions to reduce power consumption. In addition, power consumption in the clock tree is reduced because LSDFF uses a double-edge triggered operation as well as a low-swing clock. To prevent performance degradation of the LSDFF due to low-swing clock, low-V_t transistors are used for the clocked transistors without significant leakage current problems. The power saving in flip-flop operation is estimated to be 28.6% to 49.6% with additional 78% power saving in the clock network     

Level conversion for dual-supply systems

Dual-supply voltage design using a clustered voltage scaling (CVS) scheme is an effective approach to reduce chip power. The optimal CVS design relies on a level converter implemented in a flip-flop to minimize energy, delay, and area penalties due to level conversion. Additionally, circuit robustness against supply bounce is a key property that differentiates good level converter design. Novel flip-flops presented in this paper incorporate a half-latch level converter and a precharged level converter. These flip-flops are optimized in the energy-delay design space to achieve over 30% reduction of energy-delay product and about 10% savings of total power in a CVS design as compared to the conventional flip-flop. These benefits are accompanied by 24% flip-flop robustness improvement leading to 13% delay spread reduction in a CVS critical path. The proposed flip-flops also show 18% layout area reduction. Advantages of level conversion in a flip-flop over asynchronous level conversion in combinational logic are also discussed in terms of delay penalty and its sensitivity to supply bounce.     

Differential CMOS edge-triggered flip-flop based on clock racing

A differential CMOS edge-triggered flip-flop is proposed that employs a pair of cross-coupled inverters, providing fully static operation. The edge-triggering operation is achieved by a narrow pulse, produced by the clock signal and its inverted delayed version. The proposed flip-flop exhibits significant power savings of up to 25% when compared with other static differential flip-flop circuits, maintaining its speed advantage for different power supply voltages and data activity rates. It also requires only 12 transistors resulting in a reduced transistor count. Moreover, unlike the existing differential circuits, it has the ability to operate under a reduced swing clock signal without static power dissipation     

新型半静态低功耗D触发器设计

本文从简化触发器内部锁存器结构以降低功耗的要求出发，提出了一种新型的半静态D触发器设计。PSPICE模拟表明，新设计逻辑功能正确。与以往一些设计相比，新设计在功耗和速度上获得显著改进。     

新型低噪声电流型CMOS边沿触发器设计

提出以电流信号表示逻辑值的新型低噪声触发器设计,用于高性能混合集成电路的设计中以减少存贮单元开关噪声对模拟电路性能的影响。所提出的设计包括主从型边沿触发器和单闩锁单边沿触发器。单个锁存器的电流型边沿触发器设计是通过在有效时钟沿后产生的窄脉冲使锁存器瞬时导通完成一次取样求值。与主从型触发器相比,单闩锁结构的触发器具有结构简单、直流功耗低的特点。采用0.25μm CM O S工艺参数的HSP ICE模拟结果表明,所提出的电流型触发器工作时,在电源端产生的电流波动远远小于传统的CM O S电路。     

Low power double edge-triggered flip-flop using one latch

A low power double edge-triggered (DET) flip-flop using a single latch is presented. In the proposed circuit data are sampled into the latch during a short transparency period for each edge of the clock signal. The proposed flip-flop requires small silicon area and has lower power dissipation with respect to previously reported DET flip-flops     

Standby power reduction using dynamic voltage scaling and canary flip-flop structures

Lowering V/sub DD/ during standby mode reduces power by decreasing both voltage and current. Analysis of flip-flop structures shows how low the voltage can scale before destroying the state information. Measurements of a 0.13-/spl mu/m, dual-V/sub T/ test chip show that reducing V/sub DD/ to near the point where state is lost gives the best power savings. We show that "canary" flip-flops provide a mechanism for observing the proximity to failure for the flip-flops. The canary flip-flops enable closed-loop standby voltage scaling for achieving savings near the optimum. This approach potentially provides over 2/spl times/ higher savings than an optimal open-loop approach without loss of state.     

Design of high-speed bipolar flip-flops for reduced clock loading

A new topology for flip-flops is presented. A current amplifier is incorporated into a standard, current mode logic, D-type flip-flop. The gain cell effectively buffers the clock without requiring additional current. Level shifting emitter followers from the clock are reduced in size and current. The frequency response of the gain cell selectively applies a keep-alive current to the circuit at high frequency without distorting low frequency outputs. The flip-flop is configured as a static frequency divider and compared to a standard flip-flop in a bipolar SiGe process. The new circuit is faster and requires less clock power at high frequency, making it suitable for large-scale integration.     

A 9-GHz frequency divider using Si bipolar super self-aligned process technology

A very high-speed 1/8 frequency divider is fabricated, using Si bipolar super self-aligned process technology (SST), and tested. The circuit consists of three T-connected D-type master-slave flip-flops and buffers. A low voltage swing (225 mV) differential circuit technique is adopted for the first stage T-type flip-flop. The divider is capable of operating at up to 9 GHz with a power dissipation of 554 mW.     

高性能低功耗脉冲触发器设计

提出一种基于数据前瞻技术的高性能低功耗显式静态脉冲触发器(数据流触发器SJLFF).SJLFF通过减少电路内部多余跳变的次数来减少功耗损失.SJLFF不仅能减少电路内部的跳变次数而且还能通过自身改进的静态结构保持快速D到Q的延时.通过与另外一种进行了低功耗设计的触发器(CDFF)比较,在数据跳变频率为49%的情况下,SJLFF能减少25%的PDP值.     

A test circuit for measurement of clocked storage element characteristics

We present a method, on-chip test circuitry, and an error analysis, for accurate measurement of timing characteristics and power consumption of clocked storage elements. The test circuit was fabricated in 0.11 /spl mu/m CMOS technology and the measurements performed automatically using a serial scan interface. The precision and accuracy of the presented method are demonstrated by the ability to measure entire clock-to-output characteristics of flip-flops. Estimated data-to-output delay systematic measurement error is 6 ps (7%), and random error is 10 ps (11%). The method and the test circuit are applicable for delay measurements of other circuit blocks as well.