DC-DC Power Supply Design for the Computing Industry Presented by Ronil Patel 12/03/03 EE Power Electronics SJSU © 2003

Agenda Design for? Design for? Topologies used Topologies used A typical design cycle A typical design cycle Requirements Requirements Design process Design process Challenges common to the Industry Challenges common to the Industry

The Market segment Computing Telecomm Other Automotive

Computing Segment DesktopEnterprisePortableHand-held Reference: Apple Computer

Commonly Used Topologies Buck Converters Buck Converters Boost Converters Boost Converters Linear Regulators Linear Regulators <150mW - Portable designs <150mW - Portable designs 3W - Desktop designs 3W - Desktop designs

Typical Notebook Platform AC Battery Charger 5V / System Rail CPU Core Graphics 2.5V / 1.5V LCD / Inverter Reference: Apple Computer

A product design cycle Requirements Design Demo Board Testing I Production III Schematic Entry PCB Layout Fabrication Testing Stages II

Requirements - Power Static Requirements Static Requirements Vout / Iout Vout / Iout Dynamic requirements Dynamic requirements Transient loads (di/dt) Transient loads (di/dt) Voltage tolerances (Transient droop) Voltage tolerances (Transient droop)

Requirements - Product $$$ - Design cost $$$ - Design cost Available Real Estate Available Real Estate Efficiency target Efficiency target Design Reliability target Design Reliability target Lifetime (MTBF) - Servers Lifetime (MTBF) - Servers Safety (Single-fault / Current- limit) Safety (Single-fault / Current- limit) Hand-held products Hand-held products Portables Portables Project Time line Project Time line Topology selection

Design Design calculations/simulations Design calculations/simulations Switching Frequency Switching Frequency Inductance, Input/Output capacitance Inductance, Input/Output capacitance No. of Phases/FETs No. of Phases/FETs Power losses - FET, Capacitor, Inductor Power losses - FET, Capacitor, Inductor Reference: International Rectifier

Design (cont’d) Reliability Reliability De-rating / SOA curves De-rating / SOA curves Monte Carlo (Worst-case) analysis Monte 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 Selection Cost Cost Package size (typically smaller, more $$) Package size (typically smaller, more $$) Reference: Rubycon Corporation Aluminum Electrolytics Polymer Tantalum

Component Selection (cont’d) Performance Performance Variation over time Variation over time Derating Derating Voltage (Caps, FETs) Voltage (Caps, FETs) RMS current (Caps) RMS current (Caps)

Component Selection (cont’d) Vendor selection Vendor selection All the previous factors (Cost & performance) All the previous factors (Cost & performance) Reliability and quality of components Reliability and quality of components Business Reputation Business Reputation

Where are we? Preliminary design and component selection complete. Preliminary design and component selection complete. Schematic is ready --> Layout & Fabrication Schematic is ready --> Layout & Fabrication Reference: Linear Technology

Layout Guidelines Impedances for high current paths Impedances for high current paths V = L * di/dt V = L * di/dt V = R * I V = R * I Cu area for power dissipation Cu area for power dissipation Number of vias Number of vias Short Gate drive traces Short Gate drive traces Compact layout to minimize ground loops Compact layout to minimize ground loops

Development/Testing development stages development stages Schematic Entry PCB Layout Fabrication Testing Stages

Production Yield issues Yield issues Field failures Field failures Failure Analysis Design fixes

Is that it?

A zillion design challenges… Number of voltage rails Number of voltage rails Size - Portables Size - Portables Cost - Desktop Cost - Desktop Efficiency / Thermal designs Efficiency / Thermal designs

The biggest challenge.. Processor voltage requirement Processor voltage requirement Faster di/dt Faster di/dt Impedance between regulator and Processor core a growing concern Impedance between regulator and Processor core a growing concern DC regulation accuracy more predominant DC regulation accuracy more predominant

Summary Computing industry Computing industry Example of a typical platform Example of a typical platform The detailed design process The detailed design process Some key challenges faced by the industry Some key challenges faced by the industry Questions / Comments ?