Enhance EPS1U Version 2.0 Power Supply Design Guide
SSI
EPS1U Power Supply Design Guide, V2.0
EPS1U
Power Supply Design Guide
A Server System Infrastructure (SSI) Specification
For 1U Rack Chassis Power Supplies
Version 2.0
Revision History
Orig./Rev. Description of Changes Date
1.1 Initial release of EPS1U specification
2.0 Added higher power levels for 400W, 450W, and 500W power supplies.
Added a longer 355mm form factor for the 450W and 500W power levels.
Added requirements for the higher power levels: 3rd 240VA channel, output connector,
efficiency, and output loading.
Updated requirements for PSON#, PWOK, and ACWarning.
9/24/2002
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Disclaimer:
THIS SPECIFICATION IS PROVIDED "AS IS" WITH NO WARRANTIES WHATSOEVER, INCLUDING ANY WARRANTY OF
MERCHANTABILITY, NONINFRINGEMENT, FITNESS FOR ANY PARTICULAR PURPOSE, OR ANY WARRANTY OTHERWISE ARISING
OUT OF ANY PROPOSAL, SPECIFICATION OR SAMPLE. WITHOUT LIMITATION, THE PROMOTERS (Intel Corporation, Dell Computer
Corporation, Hewlett Packard Company, Silicon Graphics Inc., and International Business Machines Corporation) DISCLAIM ALL LIABILITY
FOR COST OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOST PROFITS, LOSS OF USE, LOSS OF DATA OR ANY
INCIDENTAL, CONSEQUENTIAL, DIRECT, INDIRECT, OR SPECIAL DAMAGES, WHETHER UNDER CONTRACT, TORT, WARRANTY
OR OTHERWISE, ARISING IN ANY WAY OUT OF USE OR RELIANCE UPON THIS SPECIFICATION OR ANY INFORMATION HEREIN.
The Promoters disclaim all liability, including liability for infringement of any proprietary rights, relating to use of information in this specification.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted herein.
This specification and the information herein is the confidential and trade secret information of the Promoters. Use, reproduction and
disclosure of this specification and the information herein is subject to the terms of the S.S.I. Specification Adopter's Agreement.
Copyright Intel Corporation, Dell Computer Corporation, Hewlett Packard Company , Silicon Graphics Inc., International Business Machines
Corporation, 2001.
EPS1U Power Supply Design Guide, V2.0
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EPS1U Power Supply Design Guide, V2.0
Contents
1 Purpose .....................................................................................................................................5
2 Conceptual Overview..................................................................................................................5
3 Definitions/Terms/Acronyms.......................................................................................................6
4 Mechanical Overview..................................................................................................................7
4.1 Card Edge Form Factor.......................................................................................................7
4.2 Wire Harness....................................................................................................................8
4.3 Airflow Requirements..........................................................................................................9
4.4 Temperature Requirements.................................................................................................9
5 AC Input Requirements.............................................................................................................10
5.1 AC Inlet Connector...........................................................................................................10
5.2 AC Input Voltage Specification...........................................................................................10
5.3 Input Under Voltage..........................................................................................................10
5.4 Efficiency........................................................................................................................11
5.5 AC Line Dropout ..............................................................................................................11
5.6 AC Line Fuse..................................................................................................................11
5.7 AC Inrush.......................................................................................................................12
5.8 AC Line Transient Specification..........................................................................................13
5.9 AC Line Fast Transient Specification...................................................................................13
6 DC Output Specification............................................................................................................14
6.1 Connector.......................................................................................................................14
6.1.1 Power Connector (125W, 250W, 350W, 400W)..........................................................14
6.1.2 Power Connector (450W, 500W).............................................................................16
6.2 Grounding.......................................................................................................................18
6.3 Remote Sense.................................................................................................................18
6.4 Output Power/Currents .....................................................................................................18
6.4.1 Standby Outputs ...................................................................................................22
6.5 Voltage Regulation.................................................................Error! Bookmark not defined.
6.6 Dynamic Loading.............................................................................................................22
6.7 Capacitive Loading...........................................................................................................23
6.8 Ripple / Noise..................................................................................................................23
6.9 Timing Requirements........................................................................................................24
7 Protection Circuits....................................................................................................................27
7.1 Current Limit...................................................................................................................27
7.2 240VA Protection.............................................................................................................27
7.3 Over Voltage Protection....................................................................................................28
7.4 Over Temperature Protection.............................................................................................28
8 Control and Indicator Functions................................................................................................29
8.1 PSON#...........................................................................................................................29
8.2 PWOK (Power OK)...........................................................................................................30
8.3 ACWarning.....................................................................................................................31
8.4 Field Replacement Unit (FRU) Signals ................................................................................32
8.4.1 FRU Data.............................................................................................................32
8.4.2 FRU Data Format..................................................................................................32
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8.5 LED Indicator..................................................................................................................34
EPS1U Power Supply Design Guide, V2.0
9 MTBF.......................................................................................................................................34
10 Agency Requirements...............................................................................................................35
Figures
Figure 1: Enclosure Drawing...................................................................................................................7
Figure 2: Alternate Enclosure Drawing.....................................................................................................8
Figure 3: Edge Finger Layout................................................................................................................15
Figure 4: Edge Finger Layout................................................................................................................17
Figure 5: Output Voltage Timing............................................................................................................24
Figure 6: Turn On/Off Timing (Signal Power Supply).................................................................................26
Figure 7: PSON# Signal Characteristics .................................................................................................29
Tables
Table 1: Definitions, Terms, and Acronyms (listed alphabetically).................................................................6
Table 2: Thermal Requirements ..............................................................................................................9
Table 3: AC Input Voltage Rating...........................................................................................................10
Table 4 Efficiency...............................................................................................................................11
Table 5: AC Line Sag Transient Performance..........................................................................................13
Table 6: AC Line Surge Transient Performance.......................................................................................13
Table 7: Edge Finger Pinout .................................................................................................................14
Table 8: Edge Finger Pinout .................................................................................................................16
Table 9: 125 W Load Ratings................................................................................................................19
Table 10: 250 W Load Ratings ..............................................................................................................19
Table 11: 350 W Load Ratings ..............................................................................................................20
Table 12: 400 W Load Ratings ..............................................................................................................20
Table 13: 450 W Load Ratings ..............................................................................................................21
Table 14: 500 W Load Ratings ..............................................................................................................21
Table 15: Voltage Regulation Limits.......................................................................................................22
Table 16: Optional +5V Regulation Limits ...............................................................................................22
Table 17: Transient Load Requirements.................................................................................................23
Table 18: Capacitive Loading Conditions ................................................................................................23
Table 19: Ripple and Noise...................................................................................................................23
Table 20: Output Voltage Timing...........................................................................................................24
Table 21: Turn On/Off Timing................................................................................................................25
Table 22: Over Current Protection.........................................................................................................27
Table 23: Over Current Protection.........................................................................................................28
Table 24: Over Voltage Limits...............................................................................................................28
Table 25: PSON# Signal Characteristic...................................................................................................29
Table 26: PWOK Signal Characteristics..................................................................................................30
Table 27: ACWarning Signal Characteristics ...........................................................................................31
Table 28: FRU Device Information.........................................................................................................32
Table 29: FRU Device Product Information Area......................................................................................32
Table 30: FRU Device MultiRecord Area.................................................................................................33
Table 31: LED Indicators......................................................................................................................34
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EPS1U Power Supply Design Guide, V2.0
1 Purpose
This specification defines non-redundant power supplies that support 1U rack mount entry server systems. The
entry-level power supply is not intended to be a hot swap type of power supply. The parameters of this supply are
defined in this specification for open industry use. This specification defines a 125W, 250 W and 350 W power
supply with six outputs; 3.3 V, 5 V, 12 V, -12 V, and 5 VSB. The form factor fits into a 1U system and provides a
wire harness or docking solution for output connections. An IEC connector is provided on the external face for AC
input to the power supply. The power supply contains fans for cooling, while meeting acoustic requirements.
2 Conceptual Overview
In the Entry server market, the bulk power system must source power on several output rails.
These rails are typically as follows:
• +3.3 V
• +5 V
• +12 V
• –12 V
• 5V standby
NOTE
Local DC-DC converters shall be utilized for processor power, and will ideally convert power from the +12 V
rail, however, they may also convert power from other rails.
The bulk power system may be an n+1 redundant power system or a non-redundant power system.
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EPS1U Power Supply Design Guide, V2.0
3 Definitions/Terms/Acronyms
Table 1: Definitions, Terms, and Acronyms (listed alphabetically)
Required The status given to items within this design guide, which are required to
Recommended The status given to items within this design guide which are not required to
Optional The status given to items within this design guide, which are not required to
Full Ranging A full-ranging power supply automatically senses and adjusts itself to the
CFM Cubic Feet per Minute (airflow).
Dropout A condition that allows the line voltage input to the power supply to drop to
Latch Off A power supply, after detecting a fault condition, shuts itself off. Even if the
Monotonically A waveform changes from one level to another in a steady fashion, without
MTBF Mean time between failure
Noise The periodic or random signals over frequency band of 0 Hz to 20 MHz.
Overcurrent A condition in which a supply attempts to provide more output current than
PFC Power Factor Corrected.
PWOK A typical logic level output signal provided by the supply that signals the
Ripple 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
Sag The condition where the AC line voltage drops below the 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
meet SSI guidelines and a large majority of system applications.
meet SSI guidelines, however, are required by many system applications.
meet SSI guidelines, however, some system applications may optionally
use these features.
proper input voltage range (110 VAC or 220 VAC). No manual switches or
manual adjustments are needed.
below the minimum operating voltage.
fault condition disappears the supply does not restart unless manual or
electronic intervention occurs. Manual intervention commonly includes
briefly removing and then reconnecting the supply, or it could be done
through a switch. Electronic intervention could be done by electronic
signals in the Server System.
intermediate retracement or oscillation.
the amount for which it is rated. This commonly occurs if there is a "short
circuit" condition in the load attached to the supply.
Server System that all DC output voltages are within their specified range.
10% to 95% of its nominal voltage.
conditions.
inputs of the supply.
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EPS1U Power Supply Design Guide, V2.0
Length
8.5
+/-0.3
Interior Face View
+0.2/-0.5
Exterior Face View
106.0
+/- 0.2
80.92
+0/-0.05
12.54
+/-0.3
5.0
+/-0.3
IEC Connector
AC I/P
Bi-
Color LED
IEC Connector
53.0
+/- 0.2
16.4
+/- 0.2
IEC Connector
Top View
Side View
4 Mechanical Overview
STATUS
Required
There are two physical sizes of the power supply enclosure intended to accommodate different power levels from
125W up to 500W. There are two output connector designs. A card edge solution to provide ease of installation
and removal and a wire harness to provide a traditional cabled solution. The chassis for the entry 1U power
supply is designed for use in 1U rack mounted systems.
4.1 Card Edge Form Factor
The card edge form factor is intended to allow users and manufacturers easy installation and removal of the
power supply into the system. Refer to Figure 1 for details. There are three different lengths for use with different
power levels. The recommended length for each power level is shown below.
Length Recommended power levels
215mm 125W, 250W
300mm 250W, 350W, 400W
355mm 450W, 500W
Center Line
(PWR/Fail)
40.0
Center Line
Fan
Fan
All dimensions are in millimeters.
Figure 1: Enclosure Drawing
62 32
1
31
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EPS1U Power Supply Design Guide, V2.0
Length
Interior Face
+0.2/-0.5
Exterior Face
106.0
+/- 0.2
IEC Connector
AC I/P
Bi-
Color LED
IEC Connector
53.0
+/- 0.2
16.4
+/- 0.2
IEC Connector
harness exit
4.2 Wire Harness
STATUS
Low Power Form Factor
Systems may require a wire harness connection directly from the power supply to the system. Figure 2 shows the
wire harness version details. Refer to the Entry Electronics Bay Specification at the SSI web site
(http://www.ssiforum.org/docs/entry_elecbay_spec_v2_0.pdf) for possible output connector configurations. Due
to different system board layouts the wire harness length may vary.
Center Line
(PWR/Fail)
40.0
Center Line
Fan
Fan
All dimensions are in millimeters.
Figure 2: Alternate Enclosure Drawing
Wire
location
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4.3 Airflow Requirements
STATUS
Recommended
The power supply shall have a two-speed fan(s) and provide cooling to both the supply and the system. During
low-speed fan operation, the power supply shall not exceed a noise level of 38 dBA measured at one meter on all
faces. At low fan speed, the power supply shall provide a minimum of 6 CFM of airflow with 0.003 inH2O of
system backpressure. At high fan speed, the power supply shall provide a minimum of 10 CFM with 0.006 inH2O
of system backpressure.
4.4 Temperature Requirements
STATUS
Recommended
The power supply shall operate within all specified limits over the Top temperature range. All airflow shall pass
through the power supply and not over the exterior surfaces of the power supply.
Item Description MIN MAX Units
Top Operating temperature range. 0 45
T
Non-operating temperature range. -40 70
non-op
The power supply must meet UL enclosure requirements for temperature rise limits. All sides of the power
supply, with exception to the air exhaust side, must be classified as “Handle, knobs, grips, etc. held for short
periods of time only”.
Table 2: Thermal Requirements
EPS1U Power Supply Design Guide, V2.0
°C
°C
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EPS1U Power Supply Design Guide, V2.0
5 AC Input Requirements
STATUS
Required
The power supply shall incorporate universal power input with active power factor correction, which shall reduce
line harmonics in accordance with the EN61000-3-2 and JEIDA MITI standards.
5.1 AC Inlet Connector
STATUS
Required
The AC input connector shall be an IEC 320 C-14 power inlet. This inlet is rated for 15 A / 250 VAC.
5.2 AC Input Voltage Specification
STATUS
Required
The power supply must operate within all specified limits over the following input voltage range. Harmonic
distortion of up to 10% THD must not cause the power supply to go out of specified limits. The power supply shall
operate properly at 85 VAC input voltage to guarantee proper design margins.
Table 3: AC Input Voltage Rating
Parameter MIN Rated MAX
Voltage (110) 90 V
Voltage (220) 180 V
Frequency 47 Hz 63 Hz
5.3 Input Under Voltage
STATUS
Required
The power supply shall contain protection circuitry such that application of an input voltage below the minimum
specified in section 5.2 shall not cause damage to the power supply.
100-127 V
rms
200-240 V
rms
140 V
rms
264 V
rms
rms
rms
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EPS1U Power Supply Design Guide, V2.0
5.4 Efficiency
STATUS
Recommended
The following efficiency requirements are provided as a recommendation to allow for proper power supply cooling
when installed in a system.
Power Level Efficiency Airflow (reference)
125W 65% 6 CFM
250W 68% 10 CFM
350W 72% 11 CFM
400W 74% 11 CFM
450W 74% 13 CFM
500W 75% 13 CFM
5.5 AC Line Dropout
STATUS
Required
An AC line dropout is defined to be when the AC input drops to 0 VAC at any phase of the AC line for any length
of time. During an AC dropout of one cycle or less the power supply must meet dynamic voltage regulation
requirements over the rated load. An AC line dropout of one cycle or less shall not cause any tripping of control
signals or protection circuits. If the AC dropout lasts longer than one cycle, the power supply should recover and
meet all turn on requirements. The power supply must meet the AC dropout requirement over rated AC voltages,
frequencies, and output loading conditions. Any dropout of the AC line shall not cause damage to the power
supply.
5.6 AC Line Fuse
STATUS
Required
The power supply shall incorporate one input fuse on the LINE side 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. AC inrush current shall not cause the AC line fuse to blow under any
conditions. All protection circuits in the power supply shall not cause the AC fuse to blow unless a component in
the power supply has failed. This includes DC output load short conditions.
STATUS
Optional
Table 4 Efficiency
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