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ATX12V Power Supply Design Guide
Version 2.0
3
Contents
1. Introduction ....................................................................................................... 6
1.1. Scope .....................................................................................................................................6
1.2. Key Changes for ATX12V Version 2.0 as Compared with ATX Power Supply......................6
1.2.1. Increased +12 VDC output capability ........................................................................6
1.2.2. Minimum Efficiency....................................................................................................6
1.2.3. Main Power Connector: .............................................................................................7
1.2.4. Separate current limit for 12V2 on the 2x2 connector: ...............................................7
1.3 Terminology.............................................................................................................................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 .................................................................................11
3.2. DC Output...............................................................................................................................11
3.2.1. DC Voltage Regulation ..............................................................................................11
3.2.2. Remote Sensing ........................................................................................................12
3.2.3. Typical Power Distribution .........................................................................................12
3.2.4. Power Limit / Hazardous Energy Levels....................................................................17
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. Risetime.....................................................................................................................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
3.4.2. Short-circuit Protection ..............................................................................................26