ATX Version 3.0 Multi Rail Desktop Platform Power Supply
Design Guide
ID
336521
Date
02/01/2023
Public
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Revision History
Introduction
Processor Configurations
PCI Express* Add-in Card Considerations
Electrical
Mechanical
Acoustics
Environmental
Electromagnetic Compatibility
Safety
Reliability
CFX12V Specific Guidelines 2.0
LFX12V Specific Guidelines 2.0
ATX12V Specific Guidelines 3.0
SFX12V Specific Guidelines 4.0
TFX12V Specific Guidelines 3.0
Flex ATX Specific Guidelines 2.0
DC Output – REQUIRED
DC Voltage Regulation – REQUIRED
DC Output Current – REQUIRED
Remote Sensing - RECOMMENDED
Other Low Power System Requirements
Output Ripple Noise - REQUIRED
Capacitive Load – RECOMMENDED
Closed Loop Stability - REQUIRED
+5V DC / +3.3V DC Power Sequencing - REQUIRED
Voltage Hold-Up Time - REQUIRED
12V2 DC Minimum Loading - REQUIRED
Over Voltage Protection (OVP) – REQUIRED
Short Circuit Protection (SCP) – REQUIRED
No-Load Situation – REQUIRED
Over Current Protection (OCP) – REQUIRED
Over Temperature Protection (OTP) – REQUIRED
Output Bypass – REQUIRED
Separate Current Limit for 12V2 - OPTIONAL
Overall Power Supply Efficiency Levels
Power Supply Efficiency for Energy Regulations - ENERGY STAR* and CEC (California Energy Commission) PC Computers with High Expandability Score - RECOMMENDED
SFX12V Specific Guidelines 4.0
Lower Profile Package - Physical Dimensions - REQUIRED
Fan Requirements - REQUIRED
Top Fan Mount Package - Physical Dimensions -REQUIRED
Fan Requirements - REQUIRED
Reduced Depth Top Mount Fan - Physical
Fan Requirements - REQUIRED
Standard SFX Profile Package – Physical Dimensions - REQUIRED
Fan Requirements - REQUIRED
PS3 Form Factor-Physical Dimensions - REQUIRED
Fan Requirements - REQUIRED
Timing, Housekeeping and Control – REQUIRED
Figure 4-3. Power on Timing
Table 4-9. Power Supply Timing
Description | Value | |||
Legacy Timings1 | Required | Recommended for ALPM | ||
T0 | AC power on time | - | <2s | - |
T1 | Power-on time | < 500 ms | < 200 ms | <150 ms |
T2 | Rise time | - | 0.2 – 20 ms | - |
T3 | PWR_OK delay | 100 ms2 – 500 ms | 100 ms2 – 250 ms | 100 ms2 – 150 ms |
T4 | PWR_OK rise time | - | < 10 ms | - |
T5 | AC loss to PWR_OK hold-up time3 | - | > 16 ms | - |
T6 | PWR_OK inactive to DC loss delay | - | > 1 ms | - |
- Value in the Legacy column list timings for power supplies designed before the year 2020. In 2020, the T1 and T3 timings have moved from the Legacy timing to the new Required column for all new power supply designs.
- T3 minimum time faster than 100 ms is not recommended for previous generation motherboards and systems. All design tolerances must be considered before allowing T3 faster than 100 ms.
- A T3 time less than 100 ms may be designed based on system requirements and a need to provide faster PSU and system turn on capability. However, PSU and system designers are highly recommended to verify and ensure no PSU and system compatibility problems exist, especially for previous generation motherboards and systems.
- T5 to be defined for both max/min load condition.
- PSUs are recommended to label or indicate the timing value for system designer and integrator reference for T1 and T3. This allows system designers to optimize “turn on” time within the system.