Intel ATX Guide

Document Number: 336521 - 003
ATX Multi Rail Desktop Power
Supply
Design Guide
June 2020
Revision 003

2 Design Guide
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Design Guide 3
Contents
1Introduction .....................................................................................................8
1.1 Alternative Low Power Mode for Power Supplies..........................................8
1.2 References ............................................................................................8
1.3 Terminology ..........................................................................................9
2Processor Configurations..................................................................................11
2.1 Processor Configurations – Recommended ...............................................11
2.2 High End Desktop Market Processor Considerations ...................................12
2.2.1 Modular Power Supply Connectors .............................................12
2.2.2 Overclocking Recommendations ................................................13
3Electrical .......................................................................................................14
3.1 AC Input - Required..............................................................................14
3.1.1 Input Over Current Protection – Required ...................................14
3.1.2 Inrush Current – Required ........................................................14
3.1.3 Input Under Voltage – Required ................................................14
3.2 DC Output - Required ...........................................................................15
3.2.1 DC Voltage Regulation – Required..............................................15
3.2.2 DC Output Current – Required...................................................15
3.2.3 Remote Sensing - Recommended ..............................................16
3.2.4 Other Low Power System Requirements - Recommended ..............16
3.2.5 Output Ripple Noise - Required .................................................17
3.2.6 Capacitive Load – Recommended...............................................18
3.2.7 Closed Loop Stability - Required ................................................18
3.2.8 +5V DC / +3.3V DC Power Sequencing - Required ....................... 18
3.2.9 Voltage Hold-Up Time - Required...............................................19
3.2.10 12V2 DC Minimum Loading - Required........................................19
3.3 Timing, Housekeeping, and Control – Required .........................................20
3.3.1 PWR_OK – Required ................................................................21
3.3.2 Power-Up Cross Loading Condition – Required .............................21
3.3.3 PS_ON# – Required.................................................................22
3.3.4 +5VSB – Required...................................................................23
3.3.5 Power-On Time – Required .......................................................24
3.3.6 Rise Time – Required ...............................................................24
3.3.7 Overshoot at Turn-On/Turn-Off – Required .................................25
3.4 Reset After Shutdown ...........................................................................25
3.4.1 +5VSB at Power-Down – Required.............................................25
3.4.2 +5VSB Fall Time - Recommendation ..........................................26
3.5 Output Protection .................................................................................26
3.5.1 Over Voltage Protection (OVP) – Required...................................26
3.5.2 Short Circuit Protection (SCP) – Required ...................................27
3.5.3 No-Load Situation – Required....................................................27
3.5.4 Over Current Protection (OCP) – Required...................................27
3.5.5 Over Temperature Protection (OTP) – Required ...........................27
3.5.6 Output Bypass – Required ........................................................27
3.5.7 Separate Current Limit for 12V2 - Recommended.........................27
3.5.8 Overall Power Supply Efficiency Levels .......................................28
3.5.9 Power Supply Efficiency for Energy Regulations - Energy Star* and
CEC PC Computers with High Expandability Score - Recommended.28

4 Design Guide
4Mechanical.....................................................................................................30
4.1 Labeling and Marking - Recommended ....................................................30
4.2 Connectors - Required ..........................................................................30
4.2.1 AC Connector .........................................................................30
4.2.2 DC Connectors........................................................................30
4.3 Airflow and Fans - Recommended ...........................................................35
4.3.1 Fan Location and Direction........................................................35
4.3.2 Fan Size and Speed .................................................................36
4.3.3 Venting..................................................................................36
5Acoustics .......................................................................................................37
5.1 Acoustics – Recommended ....................................................................37
6Environmental ................................................................................................38
6.1 Temperature – Recommended................................................................38
6.2 Thermal Shock (Shipping) – Recommended .............................................38
6.3 Humidity – Recommended .....................................................................38
6.4 Altitude – Recommended.......................................................................38
6.5 Mechanical Shock – Recommended .........................................................39
6.6 Random Vibration – Recommended.........................................................39
7Electromagnetic Compatibility ...........................................................................40
7.1 Emissions – Required ............................................................................40
7.2 Immunity - Required ............................................................................40
7.3 Input Line Current Harmonic Content - Optional ....................................... 40
7.4 Magnetic Leakage Field - Required ..........................................................41
7.5 Voltage Fluctuations and Flicker – Required..............................................41
8Safety ...........................................................................................................42
8.1 North America – Required......................................................................42
8.2 International – Required........................................................................43
8.3 Proscribed Materials - Required ..............................................................43
8.4 Catastrophic Failure Protection - Recommended........................................43
9Reliability ......................................................................................................44
9.1 Reliability - Recommended ....................................................................44
9.2 Reliability – PS_ON# Toggle for S0ix Mode - Required ...............................44
10 CFX12V Specific Guidelines 1.63 .......................................................................45
10.1 Physical Dimensions – Required..............................................................45
11 LFX12V Specific Guidelines 1.43........................................................................46
11.1 Physical Dimensions - Required ..............................................................46
12 ATX12V Specific Guidelines 2.53 .......................................................................49
13 SFX12V Specific Guidelines 3.43 .......................................................................51
13.1 Lower Profile Package - Physical Dimensions - Required .............................51
13.2 Fan Requirements - Required .................................................................51
13.3 Top Fan Mount Package - Physical Dimensions -Required ...........................53
13.4 Fan Requirements - Required .................................................................53
13.5 Reduced Depth Top Mount Fan - Physical .................................................54
13.6 Fan Requirements - Required .................................................................54

Design Guide 5
13.7 Standard SFX Profile Package – Physical Dimensions - Required .................. 55
13.8 Fan Requirements - Required .................................................................56
13.9 PS3 Form Factor- Physical Dimensions - Required .....................................57
13.10 Fan Requirements - Required .................................................................57
14 TFX12V Specific Guidelines 2.53........................................................................59
14.1 Physical Dimensions - Required ..............................................................59
14.2 Mounting Options - Recommended..........................................................61
14.3 Chassis Requirements - Recommended ...................................................62
15 Flex ATX Specific Guidelines 1.23 ......................................................................64
15.1 Physical Dimensions – Required..............................................................64
Figures
Figure 3-1: Differential Noise Test Setup ............................................................17
Figure 3-2: Power Supply Timing.......................................................................19
Figure 3-3: Power on Timing ............................................................................20
Figure 3-4: PS_ON# Signal Characteristics .........................................................23
Figure 3-5: +5VSB Power on Timing Versus VAC .................................................24
Figure 3-6: Rise Time Characteristics .................................................................25
Figure 3-7: 5VSB Fall Time...............................................................................26
Figure 4-1: Connectors (Pin-side View, Not to Scale)............................................31
Figure 4-2: Serial ATA* Power Connector ...........................................................35
Figure 10-1: CFX12V Mechanical Outline ............................................................45
Figure 11-1: LFX 12V Mechanical Outline............................................................46
Figure 11-2: Mechanical Details ........................................................................47
Figure 11-3: PSU Slot Feature Detail..................................................................47
Figure 11-4: Recommended Chassis Tab Feature.................................................48
Figure 12-1: Power Supply Dimensions for Chassis Not Requiring Top Venting .........49
Figure 12-2: Power Supply Dimensions for Chassis Requiring Top Venting ............... 50
Figure 13-1: 40 mm Profile Mechanical Outline....................................................52
Figure 13-2: Chassis Cutout .............................................................................52
Figure 13-3: Top Mount Fan Profile Mechanical Outline .........................................53
Figure 13-4: Chassis Cutout .............................................................................54
Figure 13-5: Recessed Fan Mounting .................................................................54
Figure 13-6: Reduced Depth Top Mount Fan Profile Mechanical Outline ...................55
Figure 13-7: Chassis Cutout .............................................................................55
Figure 13-8: 60 mm Mechanical Outline .............................................................56
Figure 13-9: Chassis Cutout .............................................................................57
Figure 13-10: PS3 Mechanical Outline ................................................................58
Figure 14-1: Mechanical Outline ........................................................................59
Figure 14-2: Dimensions and Recommended Feature Placements (Not to Scale) ...... 60
Figure 14-3: Power Supply Mounting Slot Detail ..................................................61
Figure 14-4: Fan Right and Fan Left Orientations of Power Supply in a Chassis ........62
Figure 14-5: Suggested TFX12V Chassis Cutout ..................................................62
Figure 14-6: Suggested Mounting Tab (Chassis Feature).......................................63
Figure 15-1: Mechanical Outline ........................................................................64
Figure 15-2: Dimensions and Recommended Feature Placements (Not to Scale) ...... 65

6 Design Guide
Tables
Table 1-1: Conventions and Terminology..............................................................9
Table 1-2: Support Terminology........................................................................10
Table 2-1: 12V2 Current for Processor Configurations ..........................................11
Table 3-1: AC Input Line Requirements ..............................................................14
Table 3-2: DC Output Voltage Regulation ...........................................................15
Table 3-3: DC Output Transient Step Sizes .........................................................15
Table 3-4: Recommended System DC and AC Power Consumption .........................16
Table 3-5: DC Output Noise/Ripple ....................................................................17
Table 3-6: Output Capacitive Loads ...................................................................18
Table 3-7: 12V2 DC Minimum Current................................................................19
Table 3-8: Power Supply Timing........................................................................20
Table 3-9: PWR_OK Signal Characteristics ..........................................................21
Table 3-10: PS_ON# Signal Characteristics.........................................................22
Table 3-11: Over Voltage Protection ..................................................................26
Table 3-12: Efficiency Versus Load Minimum Requirements...................................28
Table 3-13: Low Load Efficiency Requirements Increase Over Time ........................28
Table 3-14: Efficiency versus Load for Energy Star*.............................................29
Table 3-15: Efficiency Versus Load for CEC PC Computers with High Expandability
Computers* .............................................................................................29
Table 4-1: Main Power Connector Pin-Out...........................................................32
Table 4-2: Peripheral Connector Pin-Out.............................................................32
Table 4-3: Floppy Connector Pin-Out .................................................................33
Table 4-4: PCIe* Graphics Card 6 Pin Connector Pin-Out ......................................33
Table 4-5: PCI-E Graphics Card 8 Pin (6+2) Connector Pin-Out..............................33
Table 4-6: +12 V Power 4 Pin Connector Pin-Out.................................................34
Table 4-7: +12 V Power 8 Pin Connector Pin-Out.................................................34
Table 4-8: Serial ATA* Power Connector Pin-Out .................................................35
Table 5-1: Recommended Power Supply Acoustic Targets .....................................37
Table 7-1: EMC Requirement by Country ............................................................40

Design Guide 7
Revision History
Document
Number
Revision
Number
Description Revision Date
336521
001 •Initial Release September, 2017
002
•Updated Table 2-1: 12V2 Current for Processor
Configurations.
•Updated Figure 3: Power Supply Timing.
•Added Figure 5: +5VSB Power on timing versus VAC.
•Added note Table 4-8: +3.3V is removed from SATA
V3.2 spec.
•Updated Chapter 10:
−CFX12V Specific Guidelines to version 1.62
−LFX12V Specific Guidelines to version 1.42
−ATX12V Specific Guidelines to version 2.52
−SFX12V Specific Guidelines to version 3.42
−TFX12V Specific Guidelines to version 2.52
−Flex ATX Specific Guidelines to version 1.22
•Removed Chapter 16 test plan. Refer to Document
#595284 for test plan.
•Added Section 9.2. Reliability – PS_ON# toggle for S0ix
mode.
June, 2018
003
•Added Section 1.1 Alternative Low Power Mode for
Power Supplies.
•Updated Table 2-1: 12V2 Current for 10th Gen Intel®
CoreTM Processor Configurations.
•Added PSU Addendum for all future processor support
in Section 2.1.
•Update Table 3-4: 5VSB efficiency
•Updated Table 3-6: -12VDC capacitive load from
3300uF to 330uF.
•Updated Section 3.5.8 and added Table 3-13.
•Updated Section 3.5.9 to support Energy Star v8.
•Updated Section 4.3.2 for PS_ON# is asserted.
•Updated Section 9.2 Reliability – PS_ON# toggle for
S0ix mode.
•Updated Chapter 10-15:
−CFX12V Specific Guidelines to version 1.63
−LFX12V Specific Guidelines to version 1.43
−ATX12V Specific Guidelines to version 2.53
−SFX12V Specific Guidelines to version 3.43
−TFX12V Specific Guidelines to version 2.53
−Flex ATX Specific Guidelines to version 1.23
June, 2020
§ §

Introduction
8 Design Guide
1Introduction
This document provides design suggestions for various power supply form factors. The
power supplies are primarily intended for use with desktop system designs. It should
not be inferred that all power supplies must conform exactly to the content of this
document, though there are key parameters that define mechanical fit across a
common set of platforms. Since power supply needs vary depending on system
configuration, the design specifics described are not intended to support all possible
systems. The required sections are intended to be followed for all systems where the
recommended sections could be modified based on system design.
1.1 Alternative Low Power Mode for Power Supplies
Computers are continuing to change and introducing new power states. One of these
new power states is generically called an Alternative Low Power Mode (ALPM). Some
examples of Alternative Low Power Modes are Microsoft* Modern Standby or Google*
Chrome* Lucid Sleep. These new power states have created new requirements for
power supplies. Below is a summary of these requirements as they are mentioned
throughout the document.
•Section 3.2.4 – Other Lower Power System Requirements
Table 3-4 shows that ALPM requirements are at the 0.55A and 1.5A load levels.
•Section 3.3 – Timing, housekeeping and Control
Table 3-8 has a column for require values of T1 and T3 to support ALPM.
•Section 9.2 – Reliability – PS_ON# Toggle for S0ix Mode
The number of times a PSU toggles on and off is expected to increase.
1.2 References
The following documents are referenced in various sections of this design guide. The
document may not up-to-date; refer to the latest version. For guidelines not
specifically mentioned here, refer to the appropriate document.
Document Title Document
Number /Source
European Association of Consumer Electronics Manufacturers (EACEM*)
Hazardous Substance List / Certification AB13-94-146
IEEE* Recommended Practice on Surge Voltages in Low-Voltage AC Circuits ANSI* C62.41-1991
IEEE Guide on Surge Testing for Equipment Connected to Low-Voltage AC
Power Circuits ANSI C62.45-1992
Nordic national requirement in addition to EN 60950 EMKO-TSE (74-
SEC) 207/94

Introduction
Design Guide 9
Document Title Document
Number /Source
American National Standard for Methods of Measurement of Radio-Noise
Emissions from Low-Voltage Electrical and Electronic Equipment in the Range
of 9 kHz to 40 GHz for EMI testing
ANSI C63.4
UL 60950-1 First Edition –CAN/CSA-C22.2 No. 60950-1-03
First Edition,
IEC 60950-1: 2001 + Amendments and National Deviations,
EN 60950-1: 2001 + Amendment A11:
EU Low Voltage Directive (73/23/EEC) (CE Compliance)
GB-4943 (China)
CNS 14336: (Taiwan BSMI)
FCC*, Class B, Part 15 (Radiated and Conducted Emissions)
CISPR* 22 / EN55022, 5th Edition (Radiated and 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))
IEC 62368
1.3 Terminology
Table 1-1 defines the acronyms, conventions, and terminology that are used
throughout the design guide.
Table 1-1: Conventions and Terminology
Acronym/Convention
/Terminology Description
ASM
Alternative Sleep Mode, ASM replaces the traditional Sleep Mode
(ACPI S3) with a new sleep mode. An example of ASM is with
Microsoft* Modern Standby* or Lucid Sleep with Google* Chrome*
AWG American Wire Gauge
BA
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.
CFM Cubic Feet per Minute (airflow).

Introduction
10 Design Guide
Acronym/Convention
/Terminology Description
Monotonically A waveform changes from one level to another in a steady fashion,
without oscillation.
MTBF Mean time between failure.
Noise The periodic or random signals over frequency band of 0 Hz to 20
MHz.
Non-ASM Computers that do not use Alternative Sleep Mode use traditional
Sleep Mode (ACPI S3).
Overcurrent
A condition in which a supply attempts to provide more output
current than the amount for which it is rated. This commonly
occurs if there is a "short circuit" condition in the load attached to
the supply.
PFC Power Factor Correction.
P-P Peak to Peak Voltage Measurement.
PWR_OK
PWR_OK is a “power good” signal used by the system power
supply to indicate that the +5VDC, +3.3 VDC and +12VDC outputs
are above the under voltage thresholds of the power supply.
Ripple Noise The periodic or random signals over a frequency band of 0 Hz to
20 MHz.
Rise Time Rise time is defined as the time it takes any output voltage to rise
from 10% to 90% of its nominal voltage.
Surge The condition where the AC line voltage rises above nominal
voltage.
VSB or Standby Voltage An output voltage that is present whenever AC power is applied to
the AC inputs of the supply.
Table 1-2: Support Terminology
Category Description
Optional
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. May be a required or
recommended item in a future design guide.
Recommended
The status given to items within this design guide, which are not
required to meet design guide, however, are required by many
system applications. May be a required item in a future design guide.
Required
The status given to items within this design guide, which are
required to meet design guide and a large majority of system
applications.
§ §

Processor Configurations
Design Guide 11
2Processor Configurations
2.1 Processor Configurations – Recommended
The below table shows various processor configurations for 12V2 current
recommendation that should meet the values indicated.
Table 2-1: 12V2 Current for Processor Configurations
PSU 12V2 Capability Recommendations
Processor TDP Continuous
Current Peak Current
165 W 37.5 A 40.0 A
125 W 26 A 34 A
65 W 23 A 30 A
35 W 13 A 16.5 A
All future processor power / PSU Current requirements will be defined in a document
titled ATX12VO and ATX12V PSU Design Guide Addendum (# 621484) that will apply to
both Single Rail and Multi Rail ATX Power Supplies.
The above table is associated with different power level requirements of the 10th
Generation Intel Core Processor Family Datasheet for 35W, 65W and 125W skus. The
165W sku is associated with Intel® Core™ X-Series Processors.
•Peak Power called ICCMax 10 ms Max (PL4) for -S Processors
•Continuous Power called PL2 Level for -S Processors
Reference Equation for 12V2 Capability Calculation:
12V2 Peak Current = (SOC Peak Power / VR efficiency) / 11.4V
12V2 Continous Current = (SOC PL2 power / VR efficiency) / 11.4V
NOTES:
1. PSU rail voltage is 11.4V, 12V2 should be able to supply peak current for 10
ms.
2. Motherboard VR efficiency is 85% at TDC and 80% at SOC peak power (AKA
IccMax).
3. Motherboard plane resistance is 1.1 mohm.
4. If the power supply supports the 240VA Energy Hazard protection requirement
then Current levels for the 12 Volt rail above 20 Amps would have to be split
into multiple 12V rails.

Processor Configurations
12 Design Guide
2.2 High End Desktop Market Processor
Considerations
The High End Desktop market requires power supplies with higher power levels than
the mainstream market. Sometimes the EPS12V specification is referenced for these
designs. The EPS12V specification is a power supply form factor for the server market.
Here in the Desktop Power Supply design guide we are including higher power levels to
incorporate these higher performance desktop computers.
2.2.1 Modular Power Supply Connectors
For power supplies to be made for multiple end user applications it is recommended to
use a modular design with multiple cable options for the end user to decide how they
want to use power. The CPU connectors on the motherboard are either a 4 pin (2x2) or
8 pin (2x4) connector, detailed in Section 4.2.2.5 +12 V Power Connector. The
graphics card connector is either a 6 pin (2x3) or 8 pin (2x4) connector detail in
Section 4.2.2.4 PCI-Express (PCI-E) Graphics Card Connector. Both of these
connectors use the 12V rail to power the component, but use different pin locations
and keying so they are not interchangeable. Therefore, a modular design is
recommended for multiple end user possibilities.
The end user might decide to use the power supply with a lower power or non-
overclocked CPU and multiple graphics cards in the system and need more power
cables for the graphics cards. Another option is to use a higher power CPU that might
be overclocked and require more power connectors and less graphics cards in that
system. The connectors on the power supply provide 12V power and then the end user
can decide which cable to plug in to provide 12V power in their computer.
Here are some example modular designs. The orange box in each picture shows that
the connector on the power supply that provides 12V power rails.
Based on the amount of current that is needed to support a specific current (power)
level the guideline to follow is 6-8 Amps per pin. This is based on 18 AWG wire and a
solid connector pin. Based on this recommendation, here is how this can be applied to
the CPU power connectors:
•12-16A support for 2x2 (4pin) connector
•18-24A support for 2x3 (6pin) connector
•24-32A support for 2x4 (8pin) connector
This recommendation is based on common design practice. PSU and system designer
may design or use differently and should be responsible for designing the PSU to meet
all electrical, thermal, safety and reliability requirements based on the application of
the PSU.

Processor Configurations
Design Guide 13
2.2.2 Overclocking Recommendations
The power levels listed in Section 2.1 are for processors that follow the Plan Of Record
(POR) power levels that include Turbo Mode. If the processor is overclocked then
power levels will be increased. If the power supply is expected to support end users
who desire to overclock then the 12V power rail to the processor should be higher than
what is listed in Table 2-1.
§ §

Electrical
14 Design Guide
3Electrical
The following electrical requirements are required and must be met over the
environmental ranges as defined in Chapter 6 (unless otherwise noted).
3.1 AC Input - Required
The below table 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 full loading at 90 VAC.
Note: Optional - 115 VAC or 230 VAC only power supplies are an option for specific
geographical or other requirements.
Table 3-1: AC Input Line Requirements
Parameter Minimum Nominal1Maximum Unit
Vin (115 VAC) 90 115 135 VACrms
Vin (230VAC) 180 230 265 VACrms
Vin Frequency 47 - 63 Hz
NOTE: 1Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.
3.1.1 Input Over Current Protection – Required
The power supply is required to 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 – Required
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 AC switch if present, bridge rectifier, and fuse components.
Repetitive ON/OFF cycling of the AC input voltage should not damage the power supply
or cause the input fuse to blow.
3.1.3 Input Under Voltage – Required
The power supply is required to contain protection circuitry such that the application of
an input voltage below the minimum specified in the above table shall not cause
damage to the power supply.

Electrical
Design Guide 15
3.2 DC Output - Required
3.2.1 DC Voltage Regulation – Required
The DC output voltages are required to remain within the regulation ranges shown in
the below table, when measured at the load end of the output connectors under all
line, load, and environmental conditions specified in Chapter 6.
Table 3-2: DC Output Voltage Regulation
Output Range Min Nom Max Unit
+12V1DC1±5% +11.40 +12.00 +12.60 V
+12V2DC2±5% +11.40 +12.00 +12.60 V
+5VDC ±5% +4.75 +5.00 +5.25 V
+3.3VDC3±5% +3.14 +3.30 +3.47 V
-12VDC4 ±10% -10.80 -12.00 -13.20 V
+5VSB ±5% +4.75 +5.00 +5.25 V
NOTES:
1. At +12V1DC peak loading, regulation at the +12V1DC and +12V2DC outputs can go to
±5%.
2. At +12V2DC peak loading, regulation at the +12V1DC and +12V2DC outputs can go to
±5%.
3. Voltage tolerance is required at main connector and SATA connector (if used).
4. -12VDC output is optional.
3.2.2 DC Output Current – Required
The below table summarizes the expected output transient step sizes for each output.
The transient load slew rate is = 1.0 A/μs. All items in the table below are REQUIRED,
unless specifically called out as RECOMMENDED.
Table 3-3: DC Output Transient Step Sizes
Output Maximum Step Size
(% of Rated Output Amps) Maximum Step Size (A)
+12V1DC 40% (Required)
70% (Recommended) -
+12V2DC 85% -
+12V3/4 80% (Recommended)
+5VDC 30% -
+3.3VDC 30% -
-12VDC - 0.1
+5VSB - 0.5
NOTES:

Electrical
16 Design Guide
1. For example, for a rated +5 VDC output of 14A, the transient step would be
30% x 14 A = 4.2 A.
2. The numbers are based on the 10th gen Intel®CoreTM Desktop CPU family, subject to
change. Contact the Intel®representative for the up to date CPU electrical specification
max step size of the CPUs that will be assembled for system integration.
3. 12V3/V4 rails are typically used for PCI-E Graphic card connectors. Some power supplies
use one large 12V rail or other configurations. This recommendation comes from
Graphics card recommendations and should be applied to the amount of current of the
12V rails associated with the graphic card connections. This is not an Intel®requirement
and so it will be treated as a recommendation during testing.
Output voltages should remain within the regulation limits of Table 3-2, for
instantaneous changes in load as specified in Table 3-3 and for the following
conditions:
•Simultaneous load steps on the +12 VDC, +5 VDC, and +3.3 VDC outputs (all
steps occurring in the same direction).
•Load-changing repetition rate of 50 Hz to 10 kHz
•AC input range per Section 2.1 and Capacitive loading per Table 3-6.
3.2.3 Remote Sensing - Recommended
Remote sensing is recommended. Remote sensing can accurately control motherboard
loads by adding it to the PSU connector. The +3.3 VDC output should have provisions
for remote sensing to compensate for excessive cable drops. In low power PSU, remote
sensing is recommended. 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.
3.2.4 Other Low Power System Requirements - Recommended
To help meet the Blue Angel* system requirements, RAL-UZ 78, US Presidential
executive order 13221, ENERGY STAR*, ErP Lot6 requirements, and other low Power
system demands, it is recommended that the +5VSB standby supply power
consumption should be as low as possible. In order to meet the 2010 and 2013 ErP Lot
6 requirements, 2014 ErP Lot 3 requirements, and if any Computers use an Alternative
Sleep Mode (ASM) then the 5V standby efficiency should be met as shown in Table 3-4
which is measured with the main outputs off (PS_ON# high state).
Table 3-4: Recommended System DC and AC Power Consumption
5VSB
Load Target
5VSB
Actual Load
Efficiency Target
(Both 115V and 230V Input) Remark
Max / Label 3.0A / Label 75% Recommend
1.5 A 75% ALPM and ErP Lot 3 2014
1.00 A 75% Recommend
0.55 A 75% ALPM and ErP Lot 3 2014
90 mA 55% Recommend
45 mA 45% ErP Lot 6 2013

Electrical
Design Guide 17
3.2.5 Output Ripple Noise - Required
The output ripple and noise requirements listed in the below table shall be met
throughout the load ranges specified for the appropriate form factor and under all input
voltage conditions as specified in Table 3-1.
Ripple and noise are defined as periodic or random signals over a frequency band of
10 Hz to 20 MHz. Measurements shall be made with an oscilloscope with 20 MHz of
bandwidth. Outputs should be bypassed at the connector with a 0.1μF ceramic disk
capacitor and a 10 μF electrolytic capacitor to simulate system loading.
Refer to Figure 3-1 for the differential noise measurement setup.
Table 3-5: DC Output Noise/Ripple
Output Maximum Ripple and Noise (mV p-p)
+12V1DC 120
+12V2DC 120
+5VDC 50
+3.3VDC 50
-12VDC 120
+5VSB 50
Figure 3-1: Differential Noise Test Setup

Electrical
18 Design Guide
3.2.6 Capacitive Load – Recommended
The power supply should be able to power up and operate within the regulation limits
defined in Table 3-2, with the following capacitances simultaneously present on the DC
outputs.
Table 3-6: Output Capacitive Loads
Output Capacitive Load (μF)
+12V1DC 3,300
+12V2DC 3,300
+5VDC 3,300
+3.3VDC 3,300
-12VDC 330
+5VSB 3,300
3.2.7 Closed Loop Stability - Required
The power supply shall be unconditionally stable under all line/load/transient load
conditions including capacitive loads specified in Section 3.2.6. A minimum of 45
degrees phase margin and 10 dB gain margin is recommended at both the maximum
and minimum loads.
3.2.8 +5V DC / +3.3V DC Power Sequencing - Required
The +12V1 DC / +12V2 DC and +5 VDC output levels must be equal to or greater
than the +3.3 VDC output at all times during power-up and normal operation. The
time between any output of +12V1 DC / +12V2 DC and +5 VDC reaching its minimum
in-regulation level and +3.3 VDC reaching its minimum in-regulation level must be ≤
20 ms as shown in Figure 3-2.

Electrical
Design Guide 19
Figure 3-2: Power Supply Timing
3.2.9 Voltage Hold-Up Time - Required
The power supply shall maintain output regulations per Table 3-2 despite a loss of
input power at the low-end nominal range-115 VAC / 47 Hz or 230 VAC / 47 Hz – at
maximum continuous output load as applicable for a minimum of 17ms (T5+T6).
3.2.10 12V2 DC Minimum Loading - Required
The power supply +12 V2DC shall maintain output regulations per Table 3-2 and meet
minimum current values below.
Table 3-7: 12V2 DC Minimum Current
Output Minimum Current (A)
+12V2 DC 0A (Required)
+12V1 DC 0 (Recommended)

Electrical
20 Design Guide
3.3 Timing, Housekeeping, and Control – Required
Figure 3-3: Power on Timing
Table 3-8: Power Supply Timing
Parameter Description
Value
Legacy
Timings1Required Recommended
for ALPM
T0 AC power on time - <2s -
T1 Power-on time < 500ms < 200ms <150ms
T2 Rise time - 0.2 – 20ms -
T3 PWR_OK delay 100ms2– 500 ms 100ms2– 250 ms 100ms2–
150ms
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 -