484 research outputs found
A power optimization method considering glitch reduction by gate sizing
We propose a power optimization method considering glitch re-duction by gate sizing. Our method reduces not only the amount of capacitive and short-circuit power consumption but also the power dissipated by glitches which has not been exploited previously. In the optimization method, we improve the accuracy of statistical glitch estimation method and device a gate sizing algorithm that utilizes perturbations for escaping a bad local solution. The effect of our method is verified experimentally using 12 benchmark cir-cuits with a 0.5 m standard cell library. Gate sizing reduces the number of glitch transitions by 38.2 % on average and by 63.4 % maximum. This results in the reduction of total transitions by 12.8 % on average. When the circuits are optimized for power without delay constraints, the power dissipation is reduced by 7.4 % on average and by 15.7 % maximum further from the minimum-sized circuits.
Glitch Control with Dynamic Receiver Threshold Adjustment
A novel method to treat crosstalk induced glitches on local interconnects is presented. Design irregularities and manufacturing defects in system-on-chip interconnects may result in spurious electrical events that impact the reliability of the interconnect infrastructure. Conventional repeater insertion methods prove to be space and power demanding. The proposed method acts by dynamically adjusting the threshold voltage of the receiving gate without breaking the line in multiple segments. A comparative study is presented that supports the applicability of the approach
Gate-level timing analysis and waveform evaluation
Static timing analysis (STA) is an integral part of modern VLSI chip design. Table lookup based methods are widely used in current industry due to its fast runtime and mature algorithms. Conventional STA algorithms based on table-lookup methods are developed under many assumptions in timing analysis; however, most of those assumptions, such as that input signals and output signals can be accurately modeled as ramp waveforms, are no longer satisfactory to meet the increasing demand of accuracy for new technologies. In this dissertation, we discuss several crucial issues that conventional STA has not taken into consideration, and propose new methods to handle these issues and show that new methods produce accurate results. In logic circuits, gates may have multiple inputs and signals can arrive at these inputs at different times and with different waveforms. Different arrival times and waveforms of signals can cause very different responses. However, multiple-input transition effects are totally overlooked by current STA tools. Using a conventional single-input transition model when multiple-input transition happens can cause significant estimation errors in timing analysis. Previous works on this issue focus on developing a complicated gate model to simulate the behavior of logic gates. These methods have high computational cost and have to make significant changes to the prevailing STA tools, and are thus not feasible in practice. This dissertation proposes a simplified gate model, uses transistor connection structures to capture the behavior of multiple-input transitions and requires no change to the current STA tools.
Another issue with table lookup based methods is that the load of each gate in technology libraries is modeled as a single lumped capacitor. But in the real circuit, the
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gate connects to its subsequent gates via metal wires. As the feature size of integrated circuit scales down, the interconnection cannot be seen as a simple capacitor since the resistive shielding effect will largely affect the equivalent capacitance seen from the gate. As the interconnection has numerous structures, tabulating the timing data for various interconnection structures is not feasible. In this dissertation, by using the concept of equivalent admittance, we reduce an arbitrary interconnection structure into an equivalent π-model RC circuit. Many previous works have mapped the π-model to an effective capacitor, which makes the table lookup based methods useful again. However, a capacitor cannot be equivalent to a π-model circuit, and will thus result in significant inaccuracy in waveform evaluation. In order to obtain an accurate waveform at gate output, a piecewise waveform evaluation method is proposed in this dissertation. Each part of the piecewise waveform is evaluated according to the gate characteristic and load structures. Another contribution of this dissertation research is a proposed equivalent waveform search method. The signal waveforms can be very complicated in the real circuits because of noises, race hazards, etc. The conventional STA only uses one attribute (i.e., transition time) to describe the waveform shape which can cause significant estimation errors. Our approach is to develop heuristic search functions to find equivalent ramps to approximate input waveforms. Here the transition time of a final ramp can be completely different from that of the original waveform, but we can get higher accuracy on output arrival time and transition time. All of the methods mentioned in this dissertation require no changes to the prevailing STA tools, and have been verified across different process technologies
Selective Glitch Reduction Technique for Minimizing Peak Dynamic IR Drop
Abstract This paper proposes a glitch co mpensation technique which involves reducing glitch power in selected combinational cells to reduce peak current which contributes to dynamic voltage or IR drop. The proposed methodology can be seamlessly integrated to existing physical design flo ws. A glitch is an undesired transition that occurs before intended value in dig ital circuits. A glitch occurs in CMOS circu its when d ifferential delay at the inputs of a gate is greater than inertial delay, which results into increased gate switching and hence notable amount of power consumption. When such large nu mber of logic gates switch close to the same t ime they will contribute to power integrity challenge called pe ak dynamic IR drop. The glitch power is becoming more pro minent in lower technology nodes. Introduction of buffers at the input of the Logic gate may reduce glitches, but it results into large area overhead and dynamic power. In the proposed methodology we are using transmission gate as a compensation circuit to reduce extra leakage and dynamic power. A flo w is proposed for charactering the pass transistor logic to cater different delay values. The proposed methodology has been validated on a plac e and routed Multiply Accumulate (MA C) layout imp lemented using Synopsys SAED 9 0n m Generic library. Experimental results show 12% to 50% reduction in top 10 peak transient IR drop numbers with just 12% g litch power reduction in selected combinational cell instances. When compared to traditional on-chip decoupling capacitor (Decap) cells insertion method the proposed technique could reduce the peak IR drop numbers by the same amount with just 5% increase in total core capacitance
Study Of The Relationship Between Delta Delay And Adjacent Parallel Wire Length In 45 Nanometer Process Technology
Hierarchical design spans the complete framework of a design flow from Register Transfer Level (RTL), synthesis, place and route, timing closure and various other analyses before sign-off. Finer geometries and increasing interconnect density however have resulted signal integrity becoming the key issue for Deep Sub-Micron design. Post silicon bug due to noise and signal integrity can be prevented and fixed at early stage of the IC design cycle. The purpose of this research is to establish a preventive measurement for adjacent wire that can travel in parallel for 45nm technology. The intention is to ensure that a complex design can be delivered to the market with accurate, fast and trusted analysis and provide sign-off solution. Main approach is to conduct the relationship study between delta delay and adjacent parallel wire in 45 nanometer (nm) process technology and provide a preventive measurement to limit the adjacent wire can travel in parallel. The design is explored thoroughly to study the relationship between delay noise and adjacent parallel wire. The correlation is translated into an equation to estimate the delay noise produced with a certain length of adjacent parallel wire
Analysis and Design of Resilient VLSI Circuits
The reliable operation of Integrated Circuits (ICs) has become increasingly difficult to
achieve in the deep sub-micron (DSM) era. With continuously decreasing device feature
sizes, combined with lower supply voltages and higher operating frequencies, the noise
immunity of VLSI circuits is decreasing alarmingly. Thus, VLSI circuits are becoming
more vulnerable to noise effects such as crosstalk, power supply variations and radiation-induced
soft errors. Among these noise sources, soft errors (or error caused by radiation
particle strikes) have become an increasingly troublesome issue for memory arrays as well
as combinational logic circuits. Also, in the DSM era, process variations are increasing
at an alarming rate, making it more difficult to design reliable VLSI circuits. Hence, it
is important to efficiently design robust VLSI circuits that are resilient to radiation particle
strikes and process variations. The work presented in this dissertation presents several
analysis and design techniques with the goal of realizing VLSI circuits which are tolerant
to radiation particle strikes and process variations.
This dissertation consists of two parts. The first part proposes four analysis and two
design approaches to address radiation particle strikes. The analysis techniques for the
radiation particle strikes include: an approach to analytically determine the pulse width
and the pulse shape of a radiation induced voltage glitch in combinational circuits, a technique
to model the dynamic stability of SRAMs, and a 3D device-level analysis of the
radiation tolerance of voltage scaled circuits. Experimental results demonstrate that the proposed techniques for analyzing radiation particle strikes in combinational circuits and
SRAMs are fast and accurate compared to SPICE. Therefore, these analysis approaches
can be easily integrated in a VLSI design flow to analyze the radiation tolerance of such
circuits, and harden them early in the design flow. From 3D device-level analysis of the radiation
tolerance of voltage scaled circuits, several non-intuitive observations are made and
correspondingly, a set of guidelines are proposed, which are important to consider to realize
radiation hardened circuits. Two circuit level hardening approaches are also presented
to harden combinational circuits against a radiation particle strike. These hardening approaches
significantly improve the tolerance of combinational circuits against low and very
high energy radiation particle strikes respectively, with modest area and delay overheads.
The second part of this dissertation addresses process variations. A technique is developed
to perform sensitizable statistical timing analysis of a circuit, and thereby improve the
accuracy of timing analysis under process variations. Experimental results demonstrate that
this technique is able to significantly reduce the pessimism due to two sources of inaccuracy
which plague current statistical static timing analysis (SSTA) tools. Two design approaches
are also proposed to improve the process variation tolerance of combinational circuits and
voltage level shifters (which are used in circuits with multiple interacting power supply
domains), respectively. The variation tolerant design approach for combinational circuits
significantly improves the resilience of these circuits to random process variations, with a
reduction in the worst case delay and low area penalty. The proposed voltage level shifter
is faster, requires lower dynamic power and area, has lower leakage currents, and is more
tolerant to process variations, compared to the best known previous approach.
In summary, this dissertation presents several analysis and design techniques which
significantly augment the existing work in the area of resilient VLSI circuit design
INVESTIGATING THE EFFECTS OF SINGLE-EVENT UPSETS IN STATIC AND DYNAMIC REGISTERS
Radiation-induced single-event upsets (SEUs) pose a serious threat to the reliability of registers. The existing SEU analyses for static CMOS registers focus on the circuit-level impact and may underestimate the pertinent SEU information provided through node analysis. This thesis proposes SEU node analysis to evaluate the sensitivity of static registers and apply the obtained node information to improve the robustness of the register through selective node hardening (SNH) technique. Unlike previous hardening techniques such as the Triple Modular Redundancy (TMR) and the Dual Interlocked Cell (DICE) latch, the SNH method does not introduce larger area overhead. Moreover, this thesis also explores the impact of SEUs in dynamic flip-flops, which are appealing for the design of high-performance microprocessors. Previous work either uses the approaches for static flip-flops to evaluate SEU effects in dynamic flip-flops or overlook the SEU injected during the precharge phase. In this thesis, possible SEU sensitive nodes in dynamic flip-flops are re-examined and their window of vulnerability (WOV) is extended. Simulation results for SEU analysis in non-hardened dynamic flip-flops reveal that the last 55.3 % of the precharge time and a 100% evaluation time are affected by SEUs
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