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ATX12V

Enhance ATX12V Version 2.2 Power Supply Design Guide

ATX12V Power Supply Design Guide
Version 2.2
March 2005
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ATX12V Power Supply Design Guide
Revision History
Version Release Date Notes
1.0 Feb, 2000
1.1 Aug, 2000
1.2 Jan, 2002
1.3 April, 2003
2.0 February, 2003
2.01 June, 2004
• Public release
• Increase 3.3 V current; add more explanation for power sharing; do
minor edits and format fixes
• Typical Power Distribution. Change +5V loading on all power supplies distribution tables defined in DG to 0.3A
• 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.”
• Remove –5V from all power distribution tables.
• Update Power and Current guidance
• Added efficiency guidance at typical and light load
• Increased min efficiency at full load from 68% to 70%
• Serial ATA* connector definition added
• Acoustic levels added for low noise power supply design
• Reformat and update revision table
• Update Disclaimers
• Remove guidelines for ATX
• Remove guidance for –5V rail
• Updated guidance for Energy Star and stand by efficiency
• Added Terminology section
• Updated power and current guidance
• Includes 250W, 300W, 350W, and 400W guidance
• Updated cross regulation graphs
• Updated load tables
• Updated required efficiency targets. Added recommended
efficiency targets.
• Increased required minimum efficiency at typical and light load.
• Main Power Connector changes to 2x12.
• Aux power connector removed.
• Required Serial ATA Connector.
• Isolated current limit on 2x2 connector for 12V2 rail.
• Updated 3.3 V remote sense pin # on the main power connector
• Updated 12V2 DC Output Noise/Ripple information
• Removed -5V reference
• Updated 5Vsb maximum current step
• Modified 115 VAC Frequency for the Voltage Hold-up Time
2.1 March 2005
• Add 450W guidance
3
2.2 March 2005
• Current requirements updated: 250,300,350,400W
• Load table Updated
• Cross loading NEED TO UPDATE: from 250W to 450W.
• Efficiency requirements increased
• 3.3.3 5V standby current increased
• Corrected 12V2 load levels in Tables 3-7
• Added label to Figure 5
• 4.5.1 Added High Current Series wire terminals for ATX Main Power
Connector
• 4.5.2 Added High Current Series wire terminals for +12 V Power Connector
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Contents
1. Introduction .......................................................................................................8
1.1. Scope..................................................................................................................................... 8
1.2. Key Changes for ATX12V Version 2.0 and later as Compared with ATX and Pervious Versions
of ATX12V Power Supply..................................................................................................... 8
1.2.1. Increased +12 VDC output capability....................................................................... 8
1.2.2. Minimum Efficiency...................................................................................................8
1.2.2. Main Power Connector:............................................................................................ 9
1.2.3. Separate current limit for 12V2 on the 2x2 connector:.............................................9
1.3. Terminology........................................................................................................................... 9
2. Applicable Documents...................................................................................... 10
3. Electrical............................................................................................................11
3.1. AC Input................................................................................................................................. 11
3.1.1. Input Over-current Protection................................................................................... 11
3.1.2. Inrush Current Limiting ............................................................................................. 11
3.1.3. Input Under-voltage.................................................................................................. 12
3.1.4. Regulatory ................................................................................................................ 12
3.1.5. Catastrophic Failure Protection................................................................................ 13
3.2. DC Output.............................................................................................................................. 13
3.2.1. DC Voltage Regulation............................................................................................. 13
3.2.2. Remote Sensing....................................................................................................... 13
3.2.3. Typical Power Distribution........................................................................................ 13
3.2.4. Power Limit / Hazardous Energy Levels .................................................................. 20
3.2.5. Efficiency................................................................................................................... 20
3.2.6. Output Ripple/Noise.................................................................................................. 22
3.2.7. Output Transient Response...................................................................................... 24
3.2.8. Capacitive Load........................................................................................................24
3.2.9. Closed-loop Stability................................................................................................. 25
3.2.10. +5 VDC / +3.3 VDC Power Sequencing................................................................. 25
3.2.11. Voltage Hold-up Time............................................................................................. 25
3.3. Timing / Housekeeping / Control...........................................................................................25
3.3.1. PWR_OK .................................................................................................................. 26
3.3.2. PS_ON#.................................................................................................................... 26
3.3.3. +5 VSB...................................................................................................................... 27
3.3.4. Power-on Time ......................................................................................................... 28
3.3.5. Risetime.................................................................................................................... 28
3.3.6. Overshoot at Turn-on / Turn-off................................................................................ 28
3.3.7. Reset after Shutdown............................................................................................... 28
3.3.8. +5 VSB at AC Power-down ...................................................................................... 28
3.4. Output Protection................................................................................................................... 29
3.4.1. Over-voltage Protection............................................................................................ 29
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3.4.2. Short-circuit Protection ............................................................................................. 29
3.4.3. No-load Operation .................................................................................................... 29
3.4.4. Over-current Protection ............................................................................................ 29
3.4.5. Over-temperature Protection.................................................................................... 30
3.4.6. Output Bypass ..........................................................................................................30
4. Mechanical......................................................................................................... 31
4.1. Labeling / Marking................................................................................................................. 31
4.2. Physical Dimensions ............................................................................................................. 31
4.3. Airflow / Fan........................................................................................................................... 34
4.4. AC Connector........................................................................................................................ 35
4.5. DC Connectors......................................................................................................................35
4.5.1. ATX Main Power Connector..................................................................................... 37
4.5.2. +12 V Power Connector ........................................................................................... 38
4.5.3. Peripheral Connector(s) ........................................................................................... 38
4.5.4. Serial ATA Power Connector.................................................................................... 39
4.5.5. Floppy Drive Connector............................................................................................ 39
5. Environmental ................................................................................................... 40
5.1. Temperature.......................................................................................................................... 40
5.2. Thermal Shock (Shipping)..................................................................................................... 40
5.3. Humidity................................................................................................................................. 40
5.4. Altitude................................................................................................................................... 40
5.5. Mechanical Shock ................................................................................................................. 41
5.6. Random Vibration.................................................................................................................. 41
5.7. Acoustics ............................................................................................................................... 41
6. Electromagnetic Compatibility......................................................................... 42
6.1. Emissions ..............................................................................................................................42
6.2. Immunity.................................................................................................................................. 42
6.3. Input Line Current Harmonic Content and Line Flicker......................................................... 42
6.4. Magnetic Leakage Fields ...................................................................................................... 43
7. Reliability........................................................................................................... 43
7.1. Component De-rating............................................................................................................ 43
8. Safety ................................................................................................................. 43
8.1. North America........................................................................................................................ 43
8.2. International........................................................................................................................... 45
8.3. Proscribed Materials.............................................................................................................. 45
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Figures
Figure 1. Cross Loading Graph for 250W Configuration...................................................................... 15
Figure 2. Cross Loading Graph for 300W Configuration...................................................................... 16
Figure 3. Cross Loading Graph for 350W Configuration...................................................................... 17
Figure 4. Cross Loading Graph for 400W Configuration...................................................................... 18
Figure 5. Cross Loading Graph for 450W Configuration...................................................................... 19
Figure 6. Differential Noise Test Setup................................................................................................. 23
Figure 7. Power Supply Timing............................................................................................................. 25
Figure 8. PS_ON# Signal Characteristics............................................................................................. 27
Figure 9. Power Supply Dimensions for Chassis That Does Not Require Top Venting....................... 32
Figure 10. Power Supply Dimensions for Chassis That Require Top Venting..................................... 33
Figure 11. ATX12V Power Supply Connectors..................................................................................... 36
Figure 12. Serial ATA Connector..........................................................................................................39
Tables
Table 1. AC Input Line Requirements.................................................................................................. 11
Table 2. DC Output Voltage Regulation .............................................................................................. 13
Table 3. Typical Power Distribution for a 250 W ATX12V Configuration ............................................ 15
Table 4. Typical Power Distribution for a 300 W ATX12V Configuration ............................................ 16
Table 5. Typical Power Distribution for a 350 W ATX12V Configuration ............................................ 17
Table 6. Typical Power Distribution for a 400 W ATX12V Configuration ............................................ 18
Table 7. Typical Power Distribution for a 450 W ATX12V Configuration ............................................. 19
Table 8. Minimum Efficiency Vs Load.................................................................................................. 20
Table 9. Loading Table for Efficiency Measurements .......................................................................... 21
Table 10. Energy Star Input Power Consumption ................................................................................ 22
Table 12. DC Output Noise/Ripple........................................................................................................ 23
Table 13. DC Output Transient Step Sizes........................................................................................... 24
Table 14. Output Capacitive Loads....................................................................................................... 24
Table 15. PWR_OK Signal Characteristics .......................................................................................... 26
Table 16. PS_ON# Signal Characteristics........................................................................................... 27
Table 17. Over-voltage Protection........................................................................................................ 29
Table 18. Harmonic Limits, Class D Equipment................................................................................... 42
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1. Introduction
1.1. Scope
This document provides design suggestions and reference specifications for a family of
power supplies that comply with the ATX Specification, Version 2.03 and chassis. It includes supplementary information not expressly detailed in the ATX Specification, such as 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 the user’s independent design and validation activity. It should not be inferred that all ATX12V power supplies must conform exactly to the content of this document. The design specifics described herein are not intended to support all possible system configurations. System power supply needs vary widely depending on factors such as the application (that is, for desktop, workstation, or server), intended ambient environment (temperature, line voltage), or motherboard power requirements.
†
for motherboards
1.2. Key Changes for ATX12V Version 2.0 and later as Compared with ATX and Pervious Versions of ATX12V Power Supply
This section briefly summarizes the major changes made to this document that now defines ATX12V power supply. With the move to 12V voltage regulators for the processor, ATX guidelines for 5V as main power are no longer provided.
1.2.1. Increased +12 VDC output capability
System components that use 12V are continuing to increase in power. In cases where expected current requirements is greater than 18A a second 12 V rail should be made available. ATX12V power supplies should be designed to accommodate these increased +12 VDC currents.
1.2.2. Minimum Efficiency
Minimum measured efficiency is required to be 70% at full and 72% at typical (~50%) load and 65% at light (~20%) load. The recommended guidance is 77% at full load, 80% at typical (50%) load and 75% at light (20%) load to provide direction for future requirements.
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1.2.2. Main Power Connector:
The 2 x 10 main power connector has been replaced by a 2 x 12 connector. This was made to support 75 watt PCI Express*requirements. Pinout assignments are based on the SSI recommendation.
With the added 12V, 5V, and 3.3V pins the need for an Aux Power connector is no longer needed and the guidance for this connector has been removed.
1.2.3. Separate current limit for 12V2 on the 2x2 connector:
The 12V rail on the 2 x 2 power connector should be a separate current limited output to meet the requirements of UL and EN 60950.
1.3. Terminology
The following terms are used in this document:
Term Description Required
Recommended
Optional
BA
CFM Monotonically
Noise
The status given to items within this design guide, which are required to meet design guide and a large majority of system applications.
The status given to items within this design guide, which are not required to meet design guide, however, are required by many system applications.
The status given to items within this design guide, which are not required to meet design guide, however, some system applications may optionally use these features.
Declared sound power, LwAd. The declared sound power level shall be measured according to ISO* 7779 for the power supply and reported according to ISO 9296.
Cubic Feet per Minute (airflow).
A waveform changes from one level to another in a steady fashion, without intermediate retracement or oscillation.
The periodic or random signals over frequency band of 0 Hz to 20 MHz.
2. Applicable Documents
The following documents support this design guide as additional reference material.
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Document Title Description
FCC Rules Part 15, Class B Title 47, Code of Federal Regulations, Part 15 ICES-003: 1997, Class B Interference-Causing Equipment Standard – Digital Apparatus EN 55022: 1998 + Amendment
A1:2000 Class B CISPR 22: 1997, Class B
AS/NZS 3548:1995, Class B
EN 55024:1998 IEC 60950, 3rd ed., 1999 Safety of Information Technology Equipment
EN 60950: 2000 Safety of Information Technology Equipment UL 60950, 3rd ed., 2000 Safety of Information Technology Equipment CSA 22.2 No. 60950-00 Safety of Information Technology Equipment
Information Technology Equipment – Radio disturbance characteristics – Limits and methods of measurement
Information Technology Equipment – Radio disturbance characteristics – Limits and methods of measurement
Information Technology Equipment – Radio disturbance characteristics – Limits and methods of measurement
Information Technology Equipment – Immunity Characteristics – Limits and methods of measurement
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3. Electrical
The electrical requirements that follow are to be met over the environmental ranges specified in Section 5 unless otherwise noted.
3.1. AC Input
Table 1 lists AC input voltage and frequency requirements for continuous operation. The power supply shall be capable of supplying full-rated output power over two input voltage ranges rated 100-127 VAC and 200-240 VAC RMS nominal. The correct input range for use in a given environment may be either switch-selectable or auto-ranging. The power supply shall automatically recover from AC power loss. The power supply must be able to start up under peak loading at 90 VAC.
Table 1. AC Input Line Requirements
Parameter Minimum Nominal+ Maximum Unit
Vin (115 VAC) 90 115 135 VAC Vin (230 VAC) 180 230 265 VAC Vin Frequency 47 -- 63 Hz
+Note: Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.
3.1.1. Input Over-current Protection
The power supply shall incorporate primary fusing for input over-current protection to prevent damage to the power supply and meet product safety requirements. Fuses should be slow-blow–type or equivalent to prevent nuisance trips‡.
3.1.2. Inrush Current Limiting
Maximum inrush current from power-on (with power on at any point on the AC sine) and including, but not limited to, three line cycles, shall be limited to a level below the surge rating of the input line cord, AC switch if present, bridge rectifier, fuse, and EMI filter components. Repetitive ON/OFF cycling of the AC input voltage should not damage the power supply or cause the input fuse to blow.
rms
rms
‡
. For Denmark and Switzerland international safety requirements, if the internal over-current protective devices exceed 8A for Denmark and 10A for Switzerland, then the power supply must pass international safety testing to EN 60950 using a maximum 16A over-current protected branch circuit, and this 16A (time delay fuse) branch circuit protector must not open during power supply abnormal operation (output short circuit and component fault) testing.
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3.1.3. Input Under-voltage
The power supply shall contain protection circuitry such that the application of an input voltage below the minimum specified in Section 3.1, Table 1, shall not cause damage to the power supply.
3.1.4. Regulatory
The power supply is required to be tested and comply with the most current version of the following regulatory specification requirements and/or standards
PRODUCT SAFETY
UL* 60950, 3
EN*60 950, 3rd Edition
IEC*60 950, 3rd Edition (CB Report to include all national deviations)
EU* Low Voltage Directive (73/23/EEC) (CE Compliance)
rd
Edition –CAN/CSA-C22.2-60950-00,
GB4943-90 CCIB* (China)
ELECTROMAGNETIC CAMPATIBILITY
FCC*, Class B, Part 15 (Radiated & Conducted Emissions)
CISPR* 22 / EN55022, 3rd Edition (Radiated & Conducted Emissions)
EN55024 (ITE Specific Immunity)
EN 61000-4-2 – Electrostatic Discharge
EN 61000-4-3– Radiated RFI Immunity
EN 61000-4-4– Electrical Fast Transients
EN 61000-4-5 – Electrical Surge
EN 61000-4-6 – RF Conducted
EN 61000-4-8 – Power Frequency Magnetic Fields
EN 61000-4-11 – Voltage Dips, Short Interrupts and Fluctuations
EN61000-3-2 (Harmonics)
EN61000-3-3 (Voltage Flicker)
EU EMC Directive ((8/9/336/EEC) (CE Compliance)
Other Certifications and/or Declarations
GB925 (China/CCC*), CNS13438 (Taiwan/BSMI*),
AS/NZ3548 (Australia/C-tick* based on CISPR22)
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3.1.5. Catastrophic Failure Protection
Should a component failure occur, the power supply should not exhibit any of the following:
• Flame
• Excessive smoke
• Charred PCB
• Fused PCB conductor
• Startling noise
• Emission of molten material
3.2. DC Output
3.2.1. DC Voltage Regulation
The DC output voltages shall remain within the regulation ranges shown in Table 2 when measured at the load end of the output connectors under all line, load, and environmental conditions. The voltage regulation limits shall be maintained under continuous operation for any steady state temperature and operating conditions specified in Section 5.
Table 2. DC Output Voltage Regulation
Output Range Min. Nom. Max. Unit
+12V1DC +12V2DC
+5VDC ±5% +4.75 +5.00 +5.25 Volts
+3.3VDC
-12VDC ±10% -10.80 -12.00 -13.20 Volts +5VSB ±5% +4.75 +5.00 +5.25 Volts
(1)
At +12 VDC peak loading, regulation at the +12 VDC output can go to ± 10%.
(2)
Voltage tolerance is required at main connector and S-ATA connector (if used).
(3)
Minimum voltage during peak is greater than 11.0 VDC
(1)
±5% +11.40 +12.00 +12.60 Volts
(3)
±5% +11.40 +12.00 +12.60 Volts
(2)
±5% +3.14 +3.30 +3.47 Volts
3.2.2. Remote Sensing
The +3.3 VDC output should have provisions for remote sensing to compensate for excessive cable drops. The default sense should be connected to pin 13 of the main power connector. The power supply should draw no more than 10 mA through the remote sense line to keep DC offset voltages to a minimum.
3.2.3. Typical Power Distribution
DC output power requirements and distributions will vary based on specific system options and implementation. Significant dependencies include the quantity and types of
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processors, memory, add-in card slots, and peripheral bays, as well as support for advanced
graphics or other features. It is ultimately the responsibility of the designer to derive a power budget for a given target product and market.
Table 3 through Table 5 and Figure 1 through Figure 3 provide sample power distributions and a graphical recommendation for cross loading. It should not be inferred that all power supplies must conform to these tables, nor that a power supply designed to meet the information in the tables will work in all system configurations.
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