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SFX12V Power Supply Design Guide
SFX12V
Power Supply Design Guide


Version 2.3


Revision History

Version Release Date
Notes

1.0
Dec, 1997
Public release

1.1
Apr, 1998

Updated all mechanical outlines to clean up
dimensioning of mounting holes.

Added chassis cutouts for all mechanical outlines to
clarify keep-out areas.

Added Appendix C.

2.0
May, 2001

Added SFX12V description

Additional power ratings added

Updated industry standards

Increased standby current

2.1
Aug, 2001

Section 4.4 Updated Figure 4 SFX/SFX12V Connectors

Section 5.8 removed vendor name

2.2
Dec, 2001

Section 3.23 Typical Power Distribution. Change minimum
loading on 5V rail to 0.3A

Section 3.3.2 PS_ON#. Add text The power supply should not
latch into a shutdown state when PS_ON# is driven active by
pulses between 10ms to 100ms during the decay of the power
rails.



2.3
April, 2003

Reformat and update revision table

Update Disclaimers

Remove guidelines for SFX without 12V connector

Updated power and current guidance

Added efficiency targets for light and typical loading

Increased minimum Efficiency at full load from 68% to 70%

Updated guidance for standby efficiency

Added Serial ATA connector

Updated cross regulation graphs
SFX12V Power Supply Design Guide
Version 2.3

2





IMPORTANT INFORMATION AND DISCLAIMERS
INTEL CORPORATION (AND ANY CONTRIBUTOR) IS PROVIDING THIS INFORMATION AS A
CONVENIENCE AND ACCORDINGLY MAKES NO WARRANTIES WITH REGARD TO THIS DOCUMENT
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INFORMATION PROVIDED IN THIS DOCUMENT, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY
INTELLECTUAL PROPERTY RIGHTS RELATING TO THE INFORMATION OR THE IMPLEMENTATION OF
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INTEL IS NOT OBLIGATED TO PROVIDE ANY SUPPORT, INSTALLATION OR OTHER ASSISTANCE
WITH REGARD TO THE INFORMATION OR PRODUCTS MADE IN ACCORDANCE WITH THIS
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THE INFORMATION REFERRED TO IN THIS DOCUMENT IS INTENDED FOR STANDARD COMMERCIAL
USE ONLY. CUSTOMERS ARE SOLELY RESPONSIBLE FOR ASSESSING THE SUITABILITY OF THE
INFORMATION FOR USE IN PARTICULAR APPLICATIONS. THE INFORMATION IS NOT INTENDED FOR
USE IN CRITICAL CONTROL OR SAFETY SYSTEMS, MEDICAL OR LIFE SAVING APPLICATIONS, OR
IN NUCLEAR FACILITY APPLICATIONS.
NO LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL
PROPERTY RIGHTS IS GRANTED HEREIN.
Intel and Pentium are registered trademarks of Intel Corporation or its subsidiaries in the United States and
other countries.
Copyright
©
2002, 2003 Intel Corporation. All rights reserved.
*
Other names and brands may be claimed as the property of others. SFX12V Power Supply Design Guide
Version 2.3

3

Contents
1. Introduction..........................................................................................................................6

1.1. Scope...........................................................................................................................6

1.2. Changes for Version 2.3 ................................................................................................6

1.2.1. Efficiency ..........................................................................................................6

1.2.2. Increased Power ................................................................................................6

1.2.3. PS3 form factor added ......................................................................................7

1.2.4. External Fan Control - Optional............................................................................7

2. Applicable Documents .........................................................................................................8

3. Electrical ..............................................................................................................................9

3.1. AC Input........................................................................................................................9

3.1.1. Input Over-current Protection ...............................................................................9

3.1.2. Inrush Current Limiting........................................................................................9

3.1.3. Input Under Voltage............................................................................................10

3.1.4. Regulatory .........................................................................................................10

3.1.5. Catastrophic Failure Protection............................................................................10

3.2. DC Output .....................................................................................................................10

3.2.1. DC Voltage Regulation........................................................................................10

3.2.2. Remote Sensing ................................................................................................11

3.2.3. Typical Power Distribution...................................................................................12

3.2.4. Power Limit / Hazardous Energy Levels................................................................15

3.2.5. Efficiency ..........................................................................................................17

3.2.6. Output Ripple/Noise ...........................................................................................19

3.2.7. Output Transient Response.................................................................................21

3.2.8. Capacitive Load..................................................................................................21

3.2.9. Closed-loop Stability...........................................................................................22

3.2.10. +5 VDC / +3.3 VDC Power Sequencing..............................................................22

3.2.11. Voltage Hold-up Time........................................................................................22

3.3. Timing / Housekeeping / Control......................................................................................22

3.3.1. PWR_OK ..........................................................................................................23

3.3.2. PS_ON#............................................................................................................23

3.3.3. +5 VSB.............................................................................................................24

3.3.4. Power-on Time...................................................................................................25

3.3.5. Rise Time..........................................................................................................25

3.3.6. Overshoot at Turn-on / Turn-off.............................................................................25

3.3.7. Reset after Shutdown .........................................................................................25

3.3.8. +5 VSB at AC Power-down .................................................................................25

3.4. Output Protection...........................................................................................................26

3.4.1. Over Voltage Protection ......................................................................................26
SFX12V Power Supply Design Guide
Version 2.3

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3.4.2. Short-circuit Protection .......................................................................................26

3.4.3. No-load Operation ..............................................................................................26

3.4.4. Over Current Protection.......................................................................................26

3.4.5. Over-Temperature Protection ...............................................................................27

3.4.6. Output Bypass...................................................................................................27

4. Mechanical...........................................................................................................................27

4.1. Labeling / Marking..........................................................................................................27

4.2. Airflow / Fan .............................