Intel 0.9 1. Scope

Intel ATX Power Supply Design Guide

Version 0.9

1. Scope

This document outlines a reference ATX power supply that complies with the ATX Specification, Version 2.02 for motherboards and chassis. It is intended to provide additional power supply design information not detailed in the ATX 2.02 specification, including information about the physical form factor of the power supply, cooling requirements, connector configuration, and pertinent electrical and signal timing specifications.

This document is provided as a convenience only and is not intended to replace or supplement the user’s independent design and validation activity. It should not be inferred that all ATX power supplies must conform exactly to the content of this document. Neither are the design specifics described herein intended to support all possible system configurations, as system power supply needs will vary widely depending on application (desktop / workstation / server), intended ambient environment (temperature, line voltage), motherboard power requirements, etc.

With a few modifications, a standard PS/2† power supply can support an ATX form-factor system. At a high level, these modifications include consolidating various motherboard connectors into a single 20-pin connector, adding +3.3VDC and +5VSB output supply rails, adding a PS_ON# control input, and possibly repositioning the fan and/or venting locations.

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Contents

Page IMPORTANT INFORMATION AND DISCLAIMERS Contents Environmental Requirements Electromagnetic Compatibility Safety Requirements Figures Tables 1. Scope 2. Applicable Documents 3. Electrical Specification 3.1 AC Input Requirements 3.1.1 Input Overcurrent Protection 3.1.2 Inrush Current Limiting 3.1.3 Input Undervoltage 3.1.4 Immunity 3.1.4.2.3 Ring Wave, ANSI C62.45-1992 3.1.4.2.4 Electrostatic Discharge, IEC801-2/IEC1000-4-2 3.1.4.3 Radiated Immunity 3.1.4.3.1 IEC801-3/IEC 3.1.4.3.2 ENV 3.1.4.3.3 Radio Frequency Common Mode, ENV 3.2DC Output Requirements 3.2.1 DC Voltage Regulation 3.2.2Remote Sensing 3.3 Typical Power Distribution 3.3.1 Power Limit 3.3.2 Efficiency 3.3.3 Output Ripple/Noise 3.3.4 Output Transient Response 3.3.5 Capacitive Load 3.3.6 Closed Loop Stability 3.3.7 +5VDC/+3.3VDC Power Sequencing 3.3.8 Voltage Hold-upTime 3.4 Timing / Housekeeping / Control 3.4.1 PWR_OK 3.4.2 PS_ON# 3.4.3 +5VSB 3.4.4 Power-onTime 3.4.5 Risetime 3.4.6 Overshoot at Turn-on/Turn-off 3.4.7 Reset after Shutdown 3.4.8 +5VSB at AC Power Down 3.5 Output Protection 3.5.1 Overvoltage Protection 3.5.2 Short Circuit Protection 3.5.3 No Load Operation 3.5.4 Overcurrent Protection 4. Mechanical Requirements 4.1 Labeling / Marking 4.2Physical Dimensions Page Page 4.3 Airflow / Fan 4.4 AC Connector 4.5 DC Connectors 4.5.1 ATX Main Power Connector 4.5.2 Auxiliary Power Connector (for 250 W and 300 W Configurations) 4.5.3 Peripheral Connector(s) 4.5.4 Floppy Drive Connector 5. Environmental Requirements 5.1 Temperature 5.2 Thermal Shock (Shipping) 5.3 Humidity Altitude 5.6 Random Vibration 5.7 Acoustics 6. Electromagnetic Compatibility 6.1 EMI 6.2 Input Line Current Harmonic Content (Optional) 6.3 Magnetic Leakage Fields 7. Reliability 7.1 Component Derating 7.2Mean Time Between Failures (MTBF) 8. Safety Requirements 8.1 North America 8.2 International 8.3 Proscribed Materials