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DC-DC Power Supply DC-DC Power Supply DesignDesign
for the Computing for the Computing IndustryIndustry
Presented byPresented by
Ronil PatelRonil Patel
12/03/0312/03/03
EE 136 - Power ElectronicsEE 136 - Power Electronics
SJSUSJSU
© 2003© 2003
AgendaAgenda
Design for?Design for? Topologies usedTopologies used A typical design cycleA typical design cycle
RequirementsRequirements Design processDesign process
Challenges common to the IndustryChallenges common to the Industry
Computing SegmentComputing Segment
Desktop Enterprise Portable Hand-held
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Reference: Apple Computer
Commonly Used Commonly Used TopologiesTopologies
Buck ConvertersBuck Converters Boost ConvertersBoost Converters Linear RegulatorsLinear Regulators
<150mW - Portable designs<150mW - Portable designs 3W - Desktop designs3W - Desktop designs
Typical Notebook Typical Notebook PlatformPlatform
AC
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Battery Charger
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5V / System Rail
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LCD / Inverter
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Reference: Apple Computer
A product design cycleA product design cycle
Requirements
Design
Demo BoardTesting
I
Production
III
Schematic Entry
PCB Layout
Fabrication
Testing Stages
II
Requirements - Requirements - PowerPower
Static RequirementsStatic Requirements Vout / IoutVout / Iout
Dynamic requirementsDynamic requirements Transient loads (di/dt)Transient loads (di/dt) Voltage tolerances (Transient droop)Voltage tolerances (Transient droop)
Requirements - ProductRequirements - Product
$$$ - Design cost$$$ - Design cost Available Real EstateAvailable Real Estate Efficiency targetEfficiency target Design Reliability targetDesign Reliability target
Lifetime (MTBF) - ServersLifetime (MTBF) - Servers Safety (Single-fault / Safety (Single-fault /
Current-limit) Current-limit) Hand-held productsHand-held products PortablesPortables
Project Time lineProject Time line
Topology selection
DesignDesign Design calculations/simulationsDesign calculations/simulations
Switching FrequencySwitching Frequency Inductance, Input/Output capacitanceInductance, Input/Output capacitance No. of Phases/FETsNo. of Phases/FETs Power losses - FET, Capacitor, InductorPower losses - FET, Capacitor, Inductor
Reference: International Rectifier
Design (cont’d)Design (cont’d) Reliability Reliability
De-rating / SOA curvesDe-rating / SOA curves
Monte Carlo (Worst-case) analysisMonte Carlo (Worst-case) analysis Errors/Tolerances over time and temp. Errors/Tolerances over time and temp. RSS (Root Sum Square)RSS (Root Sum Square)
Reference: International Rectifier
Component SelectionComponent Selection
CostCost Package size Package size (typically smaller, more $$)(typically smaller, more $$)
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Reference: Rubycon Corporation
Aluminum ElectrolyticsPolymer Tantalum
Component Selection Component Selection (cont’d)(cont’d)
PerformancePerformance Variation over timeVariation over time
Derating Derating Voltage (Caps, FETs)Voltage (Caps, FETs) RMS current (Caps)RMS current (Caps)
Component Selection Component Selection (cont’d)(cont’d)
Vendor selection Vendor selection All the previous factors All the previous factors (Cost & (Cost &
performance)performance) Reliability and quality of componentsReliability and quality of components Business ReputationBusiness Reputation
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Where are we?Where are we?
Preliminary design and component Preliminary design and component selection complete.selection complete.
Schematic is ready --> Layout & Schematic is ready --> Layout & FabricationFabrication
Reference: Linear Technology
Layout GuidelinesLayout Guidelines
Impedances for high current pathsImpedances for high current paths V = L * di/dtV = L * di/dt V = R * IV = R * I
Cu area for power dissipationCu area for power dissipation Number of viasNumber of vias Short Gate drive tracesShort Gate drive traces Compact layout to minimize ground Compact layout to minimize ground
loopsloops
Development/TestingDevelopment/Testing
3 - 6 development stages3 - 6 development stagesSchematic Entry
PCB Layout
Fabrication
Testing Stages
ProductionProduction
Yield issuesYield issues
Field failuresField failures
Failure Analysis Design fixes
A zillion design A zillion design challenges…challenges…
Number of voltage railsNumber of voltage rails Size - PortablesSize - Portables Cost - Desktop Cost - Desktop Efficiency / Thermal designsEfficiency / Thermal designs
The biggest challenge..The biggest challenge..
Processor voltage requirementProcessor voltage requirement Faster di/dtFaster di/dt Impedance between regulator and Impedance between regulator and
Processor core a growing concernProcessor core a growing concern DC regulation accuracy more DC regulation accuracy more
predominantpredominant