Low swing dual threshold voltage domino logic

Sleep switch dual threshold voltage domino logic with reduced subthreshold and gate oxide leakage current

A variable threshold voltage keeper circuit technique is proposed for simultaneous power reduction and speed enhancement of domino logic circuits. The threshold voltage of the keeper transistor is dynamically modified during circuit operation to reduce the contention current without sacrificing noise immunity. A four-bit multiple-output domino carry generator for a carry lookahead adder is designed with the proposed circuit technique. It is shown that the variable threshold voltage keeper circuit technique enhances the circuit evaluation speed by up to 60% while reducing power dissipation by 37% as compared to a standard domino logic circuit. It is also shown that the proposed domino logic circuit technique offers 20% higher noise immunity as compared to a standard domino circuit with the same evaluation delay characteristics.

Dynamic logic is susceptible to noise, especially in the ultra-deep submicrometer dual threshold voltage technology. When the dual threshold voltage is applied to the domino logic, noise immunity must be carefully considered since the significant subthreshold current of the low threshold voltage transistor makes the dynamic node much more susceptible to noise. In the first part of this paper, we introduce a new keeper transistor sizing method to determine the optimal keeper transistor size in terms of speed, power, and noise immunity. With the use of data obtained by presimulation, it is unnecessary to simulate all the design corners corresponding to the feasible NMOS evaluation transistor size ranges to find the optimal keeper transistor size. HSPICE simulation results show that the proposed keeper transistor sizing method can be broadly applied to all the domino logic gates. In the second part of this paper, we propose a new dual threshold voltage domino logic synthesis with the keeper transistor sizing to minimize the power consumption while meeting delay and noise constraints. With the optimal keeper transistor size determined by the proposed keeper transistor sizing method, the dual threshold voltage assignment to domino logic can be simplified to the discrete threshold voltage selection. Experimental results for ISCAS85 benchmark circuits show significant savings on leakage power and active power.

As compared to static logic, domino logic circuits are always preferable for high performance circuit designs because of their less number of transistor requirement and high operational speed. Due to the presence of charge sharing problem and less noise tolerance this logic is not broadly accepted for all logic designs. The desired output of the circuit can change with a little noise pulse in the input of domino logic. Domino logic circuit has two stages first is dynamic logic part which is followed by a static inverter. This static inverter consumes very less power and has high noise immunity. In this paper a novel circuit called current mirror footed domino logic has been proposed for CMOS domino logic. This proposed domino logic is noise tolerant and has low power consumption than the basic footed and footless domino logic styles. Unity noise gain (UNG) found is also good for this logic style as compared to the previous proposed logic styles.

With the scaling of the CMOS technology, domino logic circuits experience larger leakage currents, which affect their robustness and performance. The leakage can be compensated by using a properly sized PMOS keeper transistor, at the cost of circuit delay increase. Hence, it is expected that the performance improvement of domino logic will stop in future technology nodes, due to increased required keeper size to maintain robustness. In this paper, we will study different methods of keeper sizing for comparing the performance of CMOS-OR domino logic circuits designed using Predictive Technology models of 32nm, 22nm and 16nm CMOS technology nodes. The keeper size will be adjusted to obtain the same robustness (noise immunity) across the technology generations. With this method of keeper sizing across technology nodes, the simulation results shows that indeed the delay of a low fan-in domino circuit increases from 32nm to 22nm node and the domino circuits fail to operate at 16nm node. For a high fan-in domino gate, however, the delay reduces from 32nm to 22nm; and the circuit fails at 16nm.

High performance circuits demands domino logic design. A new technique for reducing the power consumption and increasing the speed without effecting noise margin is reviewed in this paper. In this technique threshold voltage of the keeper transistor is varied using body bias generator circuit. Three different body bias generator circuits are simulated, they are dynamic body bias generator, capacitive body bias generator and cross couple capacitive body bias generator circuit. Simulations are performed on tanner EDA tool at 180 nm and 65nm technology, for carry look ahead adder. The simulation results show that CBBG and CCCBBG have reduced power consumption and delay in comparison to other circuit techniques.

We introduce a new dual threshold voltage technique for domino logic. Since domino logic is much more sensitive to noise, noise margins have to be taken into account when applying dual threshold voltages to domino logic. To guarantee the signal integrity in domino logic, we carefully consider the effect of transistor sizing and threshold voltage selection. For optimal design, tradeoffs need to be mad? among noise margin, power, and performance. Based on the characteristics of each logic gate, we propose noise and power constrained domino logic synthesis for high performance. ISCAS85 benchmark re sults show that performance can be improved up to 18.62%, with 2% active power increase, while maintaining noise margin.

Two new XOR gates are proposed. First proposed circuits adopt hybrid transistor topology in the pull-down network with all transistors being low threshold voltages. A second proposed circuit adopts hybrid topology with dual threshold voltage transistors. Simulation parameters are measured at 25°C and 110°C. First proposed circuit reduces leakage power consumption up to 50% at 25°C and 58% at 110°C as compared to standard N-type domino XOR gate. It also reduces active mode power consumption by 14% as compared to standard N-type domino XOR gate. Similarly, second proposed circuit reduces leakage power consumption up to 73% at 25°C and 90% at 110°C as compared to standard N-type domino XOR gate. It also reduces active mode power consumption by 39% as compared to standard N-type domino XOR gate.

Background/Objectives: Domino logic designs are widely used owing to its high speed and less area. However, the on chip variation of the design becomes more severe on scaling down the technology nodes. Methods/Statistical analysis: This paper details the design of variation tolerant domino logic with novel keeper architecture which comprises of a stacked grounded keeper with a body-bias generator. Furthermore, this paper elaborates the process variation tolerance techniques and compares the proposed keeper style with the existing styles. The design and analysis are carried out on wide fan-in domino logic circuits using Cadence® Spectre and Monte Carlo simulations in ADE-XL environment Findings: The results demonstrate that the novel variation tolerant keeper has an advantage of less delay compared to the conventional keeper. Additionally, it offers lesser delay variability of 7.24% and 9.18% and power variability of 14.01% and 0.15% using 180nm and 45nm technology libraries. Improvements/Applications: The proposed architecture enables the domino logic circuits to be used in applications that require robust and fast processing.

In this study a new approach for skew compensation in energy recovery clock distribution networks is introduced by manipulating the operating speed of the flip-flops. The STMicroelectronics 90 nm technology allows the use of devices with different threshold voltages, namely: high threshold voltage (HVT), standard threshold voltage (SVT) and low threshold voltage (LVT). Three types of flip-flops of equal input load: fast , standard and slow are used. Timing parameters of the flip-flops are adjusted by manipulating the switching threshold of the clock port of the flip-flops. A fast/slow flip-flop has a shorter/longer T DQ delay, compared with a standard flip-flop for the same setup time (T DCLK ). Distributing flip-flops according to their delay requirements would reduce the effect of the clock's skew on the outputs of sequentially adjacent flip-flops. Owing to the slow rise time of the sinusoidal clock signal used in energy recovery clock distribution networks compared to the conventional square-wave clock, the skew that can be compensated for in energy recovery clock distribution networks using this approach would be much higher than in square-wave clock distribution networks. This approach increases the skew bounds required by algorithms to balance the skew in the clock tree leading to reduced design complexity. Theoretical analysis and simulation results using STMicroelectronics 90 nm technology at a clock frequency of 500 MHz show that this approach is feasible and effective where a skew of up to 6.2% 1of the clock period can be compensated for in the example used. In addition, constructing clock trees using the skew slack provided in the proposed technique in a new modified differed merge embedding (DME) algorithm on five benchmarks have shown that the proposed technique enables an average reduction of 11.5% in total wire length and 53.2% reduction in the number of wire elongations. Balancing the skew in the clock tree using buffers was not considered here since inserting a buffer in the clock's path eliminates the energy recovery property. As an example of illustrating the proposed methodology, the authors have used the Elmore delay model with a selected energy recovery flip-flop to verify the practicality of the proposed scheme. Better results can be obtained by using different flip-flops. The method can generally be applied to energy recovery or square-wave clocking if different flip-flops of various speeds are used.

The dynamic circuits are supposed to offer superior speed and low power dissipation over static CMOS circuits. The domino logic circuits are used for high system performance but suffer from the precharge pulse degradation. This article provides different design topologies on the domino circuits to overcome the charge sharing and charge leakage with reference to the power dissipation and delay. The precharge keeper circuit has been proposed such that the keeper transistors also work as the precharge transistors to realize multiple output function. The performance improvement of the circuit’s analysis have been done for adders and logic gates using HSPICE tool. The proposed keeper techniques reveal lower power dissipation and lesser delay over the standard keeper circuit with less transistor count for different process variation.

As continue scaling down the transistor feature size subthreshold leakage current becomes major component of total power dissipation. This paper presents comparative analysis of different dynamic logic circuits for reducing subthreshold leakage current with improved performance in dynamic logic circuits. In this paper DOIND logic approach is proposed with and without body biasing of DOIND transistors for domino logic which reduces the leakage current with minimum delay penalty. Simulation is performed at 70 nm technology node for a different logic buffer using tanner EDA tool. Simulation results shows that reduction in leakage current by DOIND and reverse body biased (RBB) DOIND approaches are 89.72% and 89.35% respectively. Static power and energy for DOIND and RBB DOIND approaches are also improved by 45.46%, 37.07%, 45.28% and 8.66% respectively.

Domino logic finds a wide variety of applications in both static and dynamic random-access memories and in high-speed microprocessors. However, the main limitation of the domino logic-circuit family is the trade-off between the noise immunity and speed. In order to resolve such a trade-off, this paper proposes a domino logic that is based on floating-gate MOS (FGMOS) transistors. Compact-form expressions are derived for the noise margins for the low and high inputs as well as the propagation delays. The proposed scheme is verified by simulation adopting the 45 nm CMOS predictive technology model (PTM) with a power-supply voltage of 1 V. The obtained results unveil that the proposed domino logic outperforms the conventional domino logic in terms of the power-delay product and the energy-delay product when realizing wide fan-in OR gates. The realized, with the proposed scheme, 16-input OR gate has an average power consumption of 3.7 µW and a propagation delay of 51 ps.

A new low-power design method based on multiple low swing internal voltage values is proposed in this paper. It can be applied in logic circuits, which are designed with different logic family techniques such as Complementary Pass Transistor Logic (CPL), Domino Logic and Cascade Voltage Switch Logic (CVSL). The goal of this method is the reduction of the circuit power dissipation, with only a negligible increase in the area, without a reduction in the circuit operating speed. This is achieved with the replacement of a number of selected full swing voltage circuit components by low swing voltage components. The application of the proposed technique in a CPL 4-bit multiplier proved that 70% power dissipation reduction was achieved, with 30% area overhead, and no reduction in the circuit speed.

A new low-power design method based on multiple low swing internal voltage values is proposed in this paper. The proposed technique can be applied in logic circuits, which are designed with different logic family techniques such as Complementary Pass Transistor Logic (CPL), Domino Logic and Cascade Voltage Switch Logic (CVSL). The goal of this method is the reduction of the circuit power dissipation, with only a negligible increase in the area, and without a reduction in the circuit operating speed. This is achieved with the replacement of a number of selected full swing voltage circuit components by low swing voltage components. The application of the proposed technique in a CPL 4 bit multiplier proved that 30% power dissipation reduction was achieved, with 5% area overhead, and no reduction in the circuit speed.