Constraint-driven Design - The Next Step Towards Analog Design Automation Invited Talk Göran Jerke Jens Lienig Robert Bosch GmbH, AE/EIM Dresden University of Technology, IFTE Reutlingen, Germany Dresden, Germany Email: Goeran.Jerke@ieee.org Email: jens@ieee.org 1 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Motivation Evolution of Analog IC Design Verification of... Schematic Technology LVS DRC Polygon Schematic- Constraint- Analog Design ? Pushing driven Layout driven Design Synthesis 1990 2000 2010 1980 today 2 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Contents The verification gap Current approaches for constraint consideration The constraint-driven design flow Impact on design algorithms and design flow Open problems Summary and conclusion 3 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Contents The verification gap Current approaches for constraint consideration The constraint-driven design flow Impact on design algorithms and design flow Open problems Summary and conclusion 4 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Verification Gap Constraint Classification Primary Constraints Technology Constraints (manufacturing) min. wire width, spacing, overlap Functional Constraints (circuit function) max. IR-drop between two net terminals, device matching, ... Secondary Constraints Design-Methodical Constraints (design complexity) Design hierarchy, routing directions, standard cells Economic Constraints (cost, TTM) Chip count, development costs and chip area determine IC technology 5 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Verification Gap Manufacturability Layout Rules Technology Constraints DRC 1 2 (Meta layer) Verification gap Dummy errors EDA-tools guarantee manufacturability! 6 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Verification Gap Functionality Schematic Functional Constraints LVS 1 2 (Expert knowledge) (Meta layer) Devices, Unrepresentable expert knowledge parameters, nets Representable, but non-verifiable knowledge (schematic prosa, symmetries, …) EDA-tools do not (yet) guarantee circuit functionality ! 7 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Verification Gap Evolution of Analog IC Design Verification of... Constraints / Expert Knowledge Schematic Constraint Verification Technology LVS DRC Polygon Schematic- Constraint- Analog Design Pushing driven Layout driven Design Synthesis 1990 2000 2010 1980 today 8 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Contents The verification gap Current approaches for constraint consideration The constraint-driven design flow Impact on design algorithms and design flow Open problems Summary and conclusion 9 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Current Approaches for Constraint Consideration Constraint-Consideration during Schematic Design Constraints as Schematic „Prosa“ 2 nd Gen. Constraint Management + + Man. consideration of “complex” constraints Constraints are part of the database – No “complex” constraints (yet) – No autom. constraint verification possible 10 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Current Approaches for Constraint Consideration Constraint-Consideration during Physical Design „Atomic“ Module Approach Characteristics: Individual design objects ( → transistors, resistors, capacitors, etc.) and constraints are considered (semi-) automatically Constraint assignment and management is required Design algorithms must “understand” all Design Algorithms constraints + Full flexibility for layout optimization – Missing constraints result in wrong layouts – Long run-times of layout generation tools Layout variant 1 Layout variant 2 11 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Current Approaches for Constraint Consideration Constraint-Consideration during Physical Design „Molecular“ Module Approach Characteristics: Several design objects are combined to a hierarchical PCell module Constraints will be fulfilled automatically by the PCell module High-level re-use of design knowledge + Manual consideration of any constraint + Very fast constraint-driven layout generation – Additional constraints require new PCell module – Limited freedom for design optimization – Complexity of rel. PCell verification problem: O ( m n ) ( m - number of parameters, n - number of variants per parameter) PCell Module 1 PCell Module 2 12 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
Contents The verification gap Current approaches for constraint consideration The constraint-driven design flow Impact on design algorithms and design flow Open problems Summary and conclusion 13 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Constraint Representation Formalize constraints! Define all constraints explicitly! Account for design style! 14 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Simple and Complex Constraints R(Pad->T1) < 1 Ω ? R(Pad->T2) < 1 Ω ? T1 R(Pad->T3) < 1 Ω ? T3 Pad T2 Simple constraint examples: V IR (Pad->T2) < 0.1 V Voltage class (Pad) = {50V, 80V} 15 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Simple and Complex Constraints R(Pad->T1) < 1 Ω ? R(Pad->T2) < 1 Ω ? T1 R(Pad->T3) < 1 Ω ? T3 Pad T2 Complex constraint example ( independent constraints ) : if ( net type == P&G ) then [[Pad->T1], [Pad->T2], [Pad->T3]] must have star-shaped net topology && R(Pad->T1) < 1 Ω && R(Pad->T2) < 1 Ω && R(Pad->T3) < 1 Ω ! 16 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Simulation Constraint Management Start Circuit Design Constraint Floorplanning Constraint Derivation Device Generation Templates Design Constraint Data Placement Transform. Transformation Models Routing Constraint Sensitivity Constraint Analysis (CSA) Compaction Data Constraint Verification Verification Verification Rules Manufacturing Test 17 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Constraint Management (Data Consistency) Today: Separate design and DO1 constraint databases C1 DO1 DO2 V1.0 C1 DO2 DO1 Future DO3 C1 DO2 Design Constraint V2.0 Data Data – Difficult design and constraint data management (data consistency, data versioning) Design and C y - Constraint Constraint Database DO x - Design Object 18 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Constraint Management (Propagation) Top-Down Propagation Bottom-Up Propagation Top-Down and Bottom-Up Propagation T T T C1 C3 I1 I2 I1 I2 I1 I2 C2 I11 I12 I21 I22 I11 I12 I21 I22 I11 I12 I21 I22 I221 I222 I223 I221 I222 I223 I221 I222 I223 Examples: Examples: Examples: - Floorplanning constraints - Placement constraints - ESD path definition - IR-drop constraints - Routing blockages - Net shielding 19 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Constraint Derivation Methods Expert knowledge ? Direct derivation rules and templates DO1 Example: if ( differential pair ) then C1 Assign matching constraint to transistor pair DO2 ? Deduction processes Example: Net N1 is connected to 40V IO pad && I1 is connected to net N1 ⇒ I1 is connected to 40V IO pad → Assign 40V design constraints to I1 C y - Constraint Indirect method (transformation) DO x - Design Object 20 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
The Constraint-driven Design Flow Constraint Transformation Definition: Consistent and unambiguous transformation of high-level constraints into low-level constraints Example: IR-Drop 1. Transformation of electrical constraints Max. IR-Drop [V] into circuit-specific constraints 2. Transformation of circuit-specific constraints Max. Resistance [Ohm] into layout-specific constraints 3. Assignment of layout-specific constraints Wire length, -width to (geometrical) design parameters layer … 21 „Constraint-driven Design - The Next Step Towards Analog Design Automation“, ISPD’09, 2009/03/31
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