ATX/ATX12V Power Supply Design Guide
Version 1.1
Page 3
Contents
1. Introduction...................................................................................................... 6
1.1. Scope .................................................................................................................................... 6
1.2. New for ATX12V as Compared with ATX Power Supply....................................................... 6
1.2.1. ATX12V .................................................................................................................... 6
1.2.2. Increased +5 VSB Current........................................................................................ 7
2. Applicable Documents..................................................................................... 8
3. Electrical........................................................................................................... 9
3.1. AC Input................................................................................................................................. 9
3.1.1. Input Overcurrent Protection..................................................................................... 9
3.1.2. Inrush Current Limiting ............................................................................................. 9
3.1.3. Input Undervoltage....................................................................................................9
3.1.4. Immunity................................................................................................................... 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 ........................................................................................ 11
3.2.4. Power Limit............................................................................................................... 14
3.2.5. Efficiency................................................................................................................... 14
3.2.6. Output Ripple/Noise.................................................................................................. 15
3.2.7. Output Transient Response...................................................................................... 16
3.2.8. Capacitive Load........................................................................................................ 16
3.2.9. Closed-loop Stability.................................................................................................16
3.2.10. +5 VDC / +3.3 VDC Power Sequencing ................................................................. 17
3.2.11. Voltage Hold-up Time............................................................................................. 17
3.3. Timing / Housekeeping / Control........................................................................................... 17
3.3.1. PWR_OK.................................................................................................................. 17
3.3.2. PS_ON#.................................................................................................................... 18
3.3.3. +5 VSB...................................................................................................................... 19
3.3.4. Power-on Time .........................................................................................................19
3.3.5. Risetime.................................................................................................................... 19
3.3.6. Overshoot at Turn-on / Turn-off................................................................................ 20
3.3.7. Reset after Shutdown ............................................................................................... 20
3.3.8. +5 VSB at AC Power-down....................................................................................... 20
3.4. Output Protection................................................................................................................... 20
3.4.1. Overvoltage Protection ............................................................................................. 20
3.4.2. Short-circuit Protection ............................................................................................. 21
3.4.3. No-load Operation .................................................................................................... 21
3.4.4. Overcurrent Protection.............................................................................................. 21
3.4.5. Overtemperature Protection ..................................................................................... 21
3.4.6. Output Bypass .......................................................................................................... 21
