Capturing Crosstalk-Induced Waveform for Accurate Static Timing Analysis
17
Capturing Crosstalk-Induc ed Waveform for Accurate Static Timing Analysis Masanori Hashimoto , Yuji Yamada, Hidetoshi Onodera Kyoto University
description
Capturing Crosstalk-Induced Waveform for Accurate Static Timing Analysis. Masanori Hashimoto , Yuji Yamada, Hidetoshi Onodera Kyoto University. Never provide accurate waveforms. How cope with crosstalk-induced waveform?. Problems of Conventional Methods. - PowerPoint PPT Presentation
Transcript of Capturing Crosstalk-Induced Waveform for Accurate Static Timing Analysis
Capturing Crosstalk-Induced Waveform for Accurate Static Timing Analysis
Masanori Hashimoto, Yuji Yamada,Hidetoshi Onodera
Kyoto University
How cope with crosstalk-induced waveform?
Never provideaccurate waveforms
Problems of Conventional Methods
Conventionally crossing-point approach Calculate crossing timing of reference voltage
e.g. 50% delay, 20-70% transition time, etc.
Estimate large delay difference in error
almost the samewaveforms
Gate Waveform Calculation
Table look-up model Huge characterization cost Difficult to increase #parameter of
waveform
Characterization has to assume a typical waveform.
Related Works
Sasaki, ASIC/SoC Conf., 1999 Estimate delay change vs transition timing at
receiver output by circuit simulation Simulation is necessary for every instance
Sirichotiyakul, DAC, 2001 Estimate delay change at receiver output by lo
ok-up tables Library extension and characterization increas
e
Proposed Equivalent Waveform Approach
Propose equivalent waveform propagation that makes output waveforms equal Adjust both arrival time and slew
Characterization usestypical waveforms.
Derivation of Equivalent Waveform
Fitting waveforms using least square method Approximate entire outline
dttt
tgtf 2
1
)}()({2
Work well? NO!!
Problem of LSM Uniform fitting weight even for unnecessary
region misleads equivalent waveform.
Adaptive fitting for critical region is necessary.
Transition finishesbefore noise injection.
Proposed Method Improved LSM with weight coefficient
To consider output behavior
dttt dVin
dVout tgtf )()(2
2
1
slope
Noiseless waveforms Vout vs Vin curve
High gainsensitive to input
Critical Region
Higher weight
Strength of Proposed Method
No library extension No additional characterization No additional calculation except
fitting
Implemented easily with conventional STA tools
Experimental Conditions
True delay change is evaluated at Gate3 output. Conventional Method: delay change is evaluated at Gate2
input 100nm process, semi-global wire, 1mm coupled
Experimental Result （ Crosstalk ）
Agg., vic. drivers 4x, 4x, load(C1,C2)=100fF
Accurate delay variation curve is obtained.
Equivalent and Actual Waveforms
Proposed method is not misled by meaningless noise.
Cross 0.5Vdd
Conventional methodshifts waveformin error.
Agg.=vic. =4x, C1=C2=10fF
Agg.=vic. =8x, C1=C2=100fF Agg.=vic. =8x, C1=C2=10fF
Proposed method estimatesmore accurate curves thanconventional methods.
Worst case in our experiments.
Experimental Result (Crosstalk, two aggressors)
Proposed method works even when multiple aggressors.
Computational Cost
Numerical integration is necessary. #segments: accuracy vs CPU time CPU time increase is evaluated.
Path delay calculation of inverter chain File I/O and RC reduction are excluded.
3-20 #segments is accurate enough.
#segments
5 10 20 40
CPU time 1.17 1.27 1.48 1.71conventional method: 1.00
Conclusion
Propose equivalent waveform propagation scheme Cope with non-monotonic waveforms Familiar with conventional STA tools
Experimentally verify our method improves much accuracy just with 30% CPU time increase.
