Google Glass Pathology Dr. Liron Pantanowitz, MD
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Google Glass
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100X Faster Simulation - Six Sigma Optimization
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SoC Design Objectives Maximising yield • Validating greater numbers of process, voltage and temperature corners • Efficiently centering design across all PVT corners using Monte Carlo Achieving design specification • Meeting or beating performance while minimising cost of implementation • Managing greater complexity in operating and power saving modes Respin avoidance • Analog circuits are responsible for ~ 50% of IC design re-spins • Re-spins can mean missing market windows and unbudgeted costs Design porting • Moving existing circuit designs to similar technologies • Re-centering design to meet constraints of new technology 4
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Analog Design Flow • Design methodology has changed little over the years • Manual, iterative design with many SPICE runs Design specification & constraints
Define topology & resize devices
Spice
Physical layout & adjust Spice Extraction Layout verification 5
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Massively Parallel Optimization
Feasibility
Description • DC Operation • Increase Margin • Quick check • Best Design Space
Global Optimization
Description • Single Corner • Meet performance • Monte Carlo • Ready for Center
Centering
Description • All Corners • Rapid Size • Ready for P&R
AgO Optimization Strategy 6
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Database
Description • Conflict • Change Priority • System Analysis
AnXplorer Goals • • • • • •
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Quickly size W/L a circuit in a given technology Explore suitability of different design options Robust design over PVT & Monte Carlo Support all types of devices Explore results using database Optimize production yield
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AgO Design Methodology AnXplorer automates device sizing Design specification & constraints
Define topology
Feasibility Global
Physical layout & adjust
Extraction Layout verification
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Centering
Process Porting Common challenge • Port existing design in technology X (say 180 nm) to technology Y (in 180 nm) • Ensure that original design goals are met
AnXplorer approach • Start with original sized circuit • Define variable ranges for target circuit • “One click” command • Optimises and centers with new PVT corners
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Vendor A
Vendor Node Porting Vendor B
Prioritized Design Objectives • Most tools support weight-based prioritisation for multiple objectives – Designer often unsure of relative weights – bad design practice
• AnXplorer supports hierarchical design objectives – User defines relative priority
• AnXplorer achieves important objectives before optimizing low priority signals
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Implicit Objectives • Imposes implicit objectives on conditions of devices at DC operating point • Customizable Implicit objectives • Detects common sub-circuits and imposes constraints on their operating conditions • Ensures a robust DC • Available for MOS devices only
Examples of subcircuits:
• transistors in • • • • • • •
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saturation transistors in linear region current mirrors level shifters differential pairs voltage reference current mirror banks etc
Core Optimization Technology Early Optimisation tools • Frequently relied on traditional convex/gradient methods • These are known to have difficulty with multiple local minima AnXplorer • Based on advanced Evolutionary algorithm • Capable of finding global minimum in presence of many local minima • Successfully optimised tough tests Rastrigin’s function • logarithmic partitioning of design space 12
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Supports both simulation-based optimization & equation-based optimization
Multiple Local Minimum
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Trade-off Analysis Database • Finds multiple design points satisfying design objectives • Creates exploration database for postoptimization analysis – Database stores all explored design points – Query language or GUI
• Useful for trade-off analysis with conflicting objectives • Useful for “what-if” analysis 14
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Industry Standard Formats Compatible with existing design flows Un-sized circuit Schematics
Definition of Design variables
Design objectives
AnXplorer
Sized and centered net list
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Exploration database for Trade off analysis
Design Environment • Spice Simulators – – – –
Cadence Synopsys Mentor Multi-threading support
• Operating system – 64 Bit Red Hat RHEL 5
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Differentiation • Push bottom integrated technology • Robust Circuits to maximise yield –Monte Carlo • Implicit objectives for stable DC operation • Hierarchical design objectives • Trade-off analysis database • Industry standard simulators • Advanced Evolutionary Algorithm
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Contact Hillol Sarkar Hillol.Sarkar@ago-inc.com
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