ATX Version 3 Multi Rail Desktop Platform Power Supply

Design Guide

ID 336521
Date 11/01/2023
Public
Document Table of Contents

PCI-Express (PCIe*) Add-in Card Connectors (Recommended)

These are optional connectors for the power supply to support additional power needed by any PCI Express* Add-in Card (AIC). The most common PCIe* Add-in Card that uses these connectors are discrete graphics cards. The PCIe* CEM Specification defines different connectors based on the power used by the Add-in Card which can range from 75 watts up to 600 watts.

PCI Express* (PCIe*) 2x3 Auxiliary Power Connector (Recommended)

The 2x3 Power Connector is designed to provide 75 watts to the PCIe* Add-in Cards and has the following requirements:

  • Current Rating: 8.0 A/pin/position maximum to a 30 °C T-Rise above ambient temperature conditions at +12 VDC, with all six contacts energized.
  • Mated Connector Retention: 30.00 N minimum when plug pulled axially.

Cable Assembly Contact and Housing Details:

  • Housing Material: Thermoplastic
  • Pin Contact Base Material: Brass alloy or equivalent
  • Pin Contact Plating: Sn alloy
  • Flammability: UL94V-1 Minimum - Material certification or certificate of compliance is required with each lot to satisfy the Underwriters Laboratories follow-up service requirements.
  • Lead Free Soldering: Connector must be compatible with lead free soldering process.

Table 5-4: PCIe* 2x3 Auxiliary Power Connector Pin Assignment (75 watts)

Pin

Signal

Color1

Pin

Signal

Color1

1

+12V3/V4

Yellow

4

COM

Black

2

+12V3/V4

Yellow

5

Sense

Black

3

+12V3/V4

Yellow

6

COM

Black

Note:Wire Size: 18 AWG
The Sense pin on the 2x3 auxiliary power connector must be connected to ground either directly in the power supply or via a jumper to an adjacent ground pin in the connector. This pin is used by a PCI Express* 2x3 150 W/225 W/300 W Add-in Card to detect whether the 2x3 auxiliary power connector is attached.

PCI Express* (PCIe*) 2x4 Auxiliary Power Connector (Recommended)

The 2x4 Auxiliary Power Connector consists of a PCB Header, mounted on a PCIe* Add-in Card, and a mating 2x4 Cable Plug harness. The 2x4 PCB header is designed to accept both the mating 2x4 Cable Plug as well as the 2x3 cable plug, for backward-compatibility. The Add-in Card PCB Header is keyed to ensure that a 2x3 cable plug from a PSU will be properly aligned when it is mated with a 2x4 PCB Header. Two Sense pins in the 2x4 PCB header allow the PCIe* Add-in Cards to detect the power available from the cable. The 2x4 Cable Plug asserts (grounds) two sense pins to indicate that 150 watts are available to the PCIe* Add-in Card through this cable, while the 2x3 plug asserts only one sense pin, to signal that only 75 watts may be drawn from the cable. The 2x4 Cable Plug has the following requirements:

  • Current Rating: 7.0 A per pin/position maximum to a 30 °C T-Rise above ambient temperature conditions at +12 VDC with all eight contacts energized.
  • Mated Connector Retention: 30.00 N minimum when plug is pulled axially.

Cable Assembly Contact and Housing Details:

  • Housing Material: Thermoplastic; Note that this connector has unique mechanical keying to avoid incorrect insertion of a cable plug intended for a different type of connector.
  • Pin Contact Base Material: Brass alloy or equivalent
  • Pin Contact Plating: Sn alloy
  • Flammability: UL94V-1 Minimum - Material certification or certificate of compliance is required with each lot to satisfy the Underwriters Laboratories follow-up service requirements.
  • Lead Free Soldering: Connector must be compatible with lead free soldering process.

Table 5-5: PCIe* 2x4 Auxiliary Power Connector Pin Assignment (150 Watts)

Pin

Signal

Color1

Pin

Signal

Color1

1

+12V3/V4

Yellow

5

COM

Black

2

+12V3/V4

Yellow

6

SENSE0

Black

3

+12V3/V4

Yellow

7

COM

Black

4

SENSE1

Black

8

COM

Black

Note:18 AWG wire.

Table 5-6: PCIe* 2x4 Auxiliary Power Connector Sense Pin Decoding by AIC

Sense 1

Sense 0

Description

Ground

Ground

A 2x4 connector is plugged into the card. The card can draw up to 150 W from the auxiliary power connector

Ground

Open

Reserved

Open

Ground

A 2x3 connector is plugged into the card. The card can only draw up to 75 W from the auxiliary power connection

Open

Open

No auxiliary power connector is plugged in

For a sense pin that needs to be grounded, it must be connected to ground either directly in the power supply or via a jumper to an adjacent ground pin in the connector.

PCI Express* (PCIe*) 12V-2x6 Auxiliary Power Connector (Optional for PSU ≤ 450 watts, Recommended for PSU > 450 watts)

The 12V-2x6 Auxiliary Power connector is designed to deliver up to 600 watts of 12V power directly to a PCIe* Add-in Card. This power connector is not compatible with the 2x3 or 2x4 auxiliary power connectors. The 12V-2x6 connector power pins have a 3.0 mm spacing, while the contacts in a 2x3 and 2x4 connector lie on a larger 4.2 mm pitch. The 12V-2x6 auxiliary power connector includes twelve large contacts to carry power and four smaller contacts beneath, to carry the sideband signals.

The two mating components of the 12V-2x6 are the Cable Plug, which terminates the cable harness, and the PCB Header, which is mounted on the Add-in Card and, optionally, within a modular power supply.

The connector performance requirements are as follows:

  • Power Pin Current Rating: (Excluding sideband contacts) 9.2 A per pin/position with a limit of a 30 °C T-Rise above ambient temperature conditions at +12 VDC with all twelve contacts energized. The connector body must display a label or embossed H++ characters to indicate support of 9.2 A/pin or greater. Refer to Figure 5-5 for the approximate positioning of the H++ marker on the 12V-2x6 Right Angle (R/A) PCB Header.

• Mated Connector Latch Retention: 45.00 N minimum when plug pulled axially.

The 12V-2x6 cable plug housing has been defined with two options that provide different physical shroud designs for the sideband signals, as shown in Figure 5-3. The thumb-ridge feature is present on one design (Option 1) and absent on the other (Option 2).

Figure 5-3: 12V-2x6 Cable Plug Connector

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Figure 5-4: 12V-2x6 Cable Assembly

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The cable plug connector housing for the 12V-2x6 connector has all dimensions shown in mm. Slight changes to this connector that do not affect connector mating are permitted. Reference latest PCI-SIG documentation for latest information about this connector.

12V-2x6 Cable Plug Assembly Contact and Housing Details:

  • Housing Material: Thermoplastic Glass Fiber Filled, UL94V-0
  • Color: Black
  • Pin Contact Material: Copper Alloy
  • Power Pin Contact Plating: Tin plated on contact area
  • Signal Pin Contact Plating: Tin plated on contact area
  • All dimensions are in mm
  • Connector must be compatible with a lead-free soldering process.

Wire Details:

  • Power/Ground Pin Wire Size: 16 AWG
    • All 12 pins must be connected to the power supply using 16 AWG cable, with no depopulation
  • Sideband Signals Pin Wire Size: 28 AWG

If a power supply uses a modular cable connection, an additional 12V-2x6 PCB Header connector will be required in the housing of the power supply to accept “double-ended” 12V-2x6 cables. Details below are provided via the PCIe CEM Revision 5.1 Specification.

Special Note on 12V-2x6 vs. 12VHPWR connectors

The 12V-2x6 PCB connector is labeled with a “H++” to differentiate it from the previously defined 12VHPWR connector, which was labelled with the “H+” symbol.

The 12VHPWR connector, introduced in the earlier 2.0 revision of this document and the PCIe CEM 5.0 Specification, has been deprecated and replaced with the 12V-2x6 connector, as shown in th PCIe CEM 5.1 specification. While the 12V-2x6 connector specification is mechanically identical to the 12VHPWR connector in most respects, multiple updates have been incorporated into the newer, 12V-2x6 connector, to improve its reliability.

The chief improvements introduced in the 12V-2x6 connector include:

    • The power pins have been lengthened and the sideband pins have been shortened in the PCB Header to ensure first-mate/last break engagement of the power pins. This mechanical revision is present in the 12V-2x6 PCB header component to ensure that the sideband pins engage only after the power pins are sufficiently mated.
    • The sideband signals SENSE0/SENSE1 definitions, which signal maximum available power available from the PSU, have been updated, as shown in Table 3-5.
      • The 150 watts power level now requires the SENSE0/SENSE1 pins to be shorted together in the power supply or the cable.
      • When both SENSE0/SENSE1 are unasserted, as defined by their high-impedance Open-Open state, no power may be drawn by the load. This is new SENSE0/SENSE1 combination now defines the new 0 watt state, which was not present in the 12VHPWR connector. These updated SENSE0/SENSE1 combinations ensure that an Add-in Card may only draw power only when the power pins and the sideband pins are engaged and correctly asserted. The Open-Open condition signals that the PCB plug is either poorly seated or absent. These two conditions are now functionally equivalent. A PCIe CEM 5.1 Add-in Card will explicitly interpret the Open-Open SENSE0/SENSE1 stat as the 0 watt configuration, and it will not attempt to draw power from the cable.
    • It is important that the power supply provide these updated SENSE0/SENSE1 encodings to the cable, to ensure compatibility with PCIe CEM 5.1 compliant Add-in Cards. See 3.3.1 for more details on SENSE0/SENSE1 encoding.

Figure 5-5: 12V-2x6 PCB Header

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Figure 5-6: 12V-2x6 PCB Header Dimensions – Front View

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Figure 5-7: 12V-2x6 PCB Header – Side View

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Figure 5-8: 12V-2x6 PCB Header – Side View, Highlighting Contact Dimensions