Section 7.2 – Changed over current protection table (added +12V3 peak value)
8/21/2002
5/18/2003
SSI
EPS1U Power Supply Design Guide, V2.1
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, NEC
Corporation, Dell Computer Corporation, Data General a division of EMC Corporation, Compaq Computer Corporation, Silicon Graphics Inc.,
and International Business Machines Corporation) DISCLAIM ALL LIABILITY FOR COST OF PROCUREMENT OF SUBSTITUTE GOODS
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Copyright Intel Corporation, Dell Computer Corporation, Hewlett Packard Company, Silicon Graphics Inc., International Business Machines
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
5.5 AC Line Dropout ............................................................................................................................... 11
5.6 AC Line Fuse .................................................................................................................................... 12
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
7.1 Current Limit ..................................................................................................................................... 26
8.3 AC Warning....................................................................................................................................... 29
8.4 Field Replacement Unit (FRU) Signals............................................................................................. 30
8.4.2 FRU Data Format .................................................................................................................30
8.5 LED Indicator .................................................................................................................................... 32
Table 22: Over Current Protection.......................................................................................................................... 26
Table 23: Over Current Protection.......................................................................................................................... 27
Table 24: Over Voltage Limits ................................................................................................................................ 27
Table 25: PSON# Signal Characteristic .................................................................................................................. 28
Table 26: PWOK Signal Characteristics................................................................................................................. 29
Table 27: ACWarning Signal Characteristics ......................................................................................................... 29
Table 28: FRU Device Information ......................................................................................................................... 30
Table 29: FRU Device Product Information Area ................................................................................................... 30
Table 30: FRU Device MultiRecord Area ............................................................................................................... 31
Table 31: LED Indicators ........................................................................................................................................ 32
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EPS1U Power Supply Design Guide, V2.1
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 power supplies ranging from 125 W
to 500 W, 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, V2.1
3 Definitions/Terms/Acronyms
Table 1: Definitions, Terms, and Acronyms (listed alphabetically)
Required
Recommended
Optional
Full Ranging
CFM
Dropout
Latch Off
Monotonically
MTBF
Noise
Overcurrent
PFC
PWOK
Ripple
Rise Time
Sag
Surge
VSB or Standby Voltage
The status given to items within this design guide, which are required to
meet SSI guidelines and a large majority of system applications.
The status given to items within this design guide which are not required to
meet SSI guidelines, however, are required by many system applications.
The status given to items within this design guide, which are not required to
meet SSI guidelines, however, some system applications may optionally
use these features.
A full-ranging power supply automatically senses and adjusts itself to the
proper input voltage range (110 VAC or 220 VAC). No manual switches or
manual adjustments are needed.
Cubic Feet per Minute (airflow).
A condition that allows the line voltage input to the power supply to drop to
below the minimum operating voltage.
A power supply, after detecting a fault condition, shuts itself off. Even if the
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.
A waveform changes from one level to another in a steady fashion, without
intermediate retracement or oscillation.
Mean time between failure
The periodic or random signals over frequency band of 0 Hz to 20 MHz.
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.
Power Factor Corrected.
A typical logic level output signal provided by the supply that signals the
Server System that all DC output voltages are within their specified range.
The periodic or random signals over a frequency band of 0 Hz to 20 MHz.
Rise time is defined as the time it takes any output voltage to rise from
10% to 95% of its nominal voltage.
The condition where the AC line voltage drops below the nominal voltage
conditions.
The condition where the AC line voltage rises above nominal voltage.
An output voltage that is present whenever AC power is applied to the AC
inputs of the supply.
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EPS1U Power Supply Design Guide, V2.1
4 Mechanical Overview
STATUS
Required
There are three physical sizes of the power supply enclosure intended to accommodate different power levels
from 125W up to 550W. Two output connector designs are defined, also. A card edge solution provides ease of
installation and removal, while the wire harness design provides a traditional cabled solution. The enclosure of
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 – 230W
300mm 250W – 450W
40.0
355mm 450W – 550W
+/- 0.
53.0
+/- 0.
106.0
Bi-Color LED
(PWR/Fail)
+0.2/-0.
16.4
Fan
Exterior Face View
+/- 0.
IEC Connector
Center Line
C I/P
Fan
Top View
IEC Connector
+0/-0.
IEC Connector
Center Line
80.92
12.54
+/-0.
+/-0.
8.5
Length
Side View
ll dimensions are in millimeters.
+/-0.
5.0
62 32
1
31
Interior Face View
Figure 1: Enclosure Drawing
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EPS1U Power Supply Design Guide, V2.1
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 EPS2U specification on the SSI web site (http://www.ssiforum.org) for
possible output connector configurations. Due to different system board layouts the wire harness length may
vary.
40.0
Bi-Color LED
(PWR/Fail)
+0.2/-0.
16.4
Fan
Exterior Face
+/- 0.
+/- 0.
53.0
IEC Connector
Center Line
AC I/P
Fan
106.0
+/- 0.
IEC Connector
IEC Connector
Center Line
Length
ll dimensions are in millimeters.
Optional fan
placement
Wire
harness exit
location
Interior Face
Figure 2: Alternate Enclosure Drawing
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EPS1U Power Supply Design Guide, V2.1
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.
Table 2: Thermal Requirements
Item Description MIN MAX Units
Top Operating temperature range. 0 50
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”.
°C
°C
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EPS1U Power Supply Design Guide, V2.1
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 Rating
PARAMETER MIN RATED MAX
Voltage (110) 90 V
Voltage (220) 180 V
Frequency 47 Hz 63 Hz
100-127 V
rms
200-240 V
rms
140 V
rms
264 V
rms
rms
rms
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.
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EPS1U Power Supply Design Guide, V2.1
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.
Table 4: Efficiency
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.
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EPS1U Power Supply Design Guide, V2.1
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
Some system applications may require a second input fuse in the NEUTRAL side of the AC input. In this case
two fuses would be required; one in the LINE side and one in the NEUTRAL side of the AC inlet to the power
supply.
5.7 AC Inrush
STATUS
Required
The power supply must meet inrush requirements for any rated AC voltage, during turn on at any phase of AC
voltage, during a single cycle AC dropout condition, during repetitive ON/OFF cycling of AC, and over the
specified temperature range (T
(including input fuse, bulk rectifiers, and surge limiting device).
STATUS
Recommended
An additional inrush current limit is recommended for some system applications that require multiple systems on a
single AC circuit. AC line inrush current shall not exceed 30 A peak for one-quarter of the AC cycle, after which,
the input current should be no more than the specified maximum input current from Table 3.
). The peak inrush current shall be less than the ratings of its critical components
op
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EPS1U Power Supply Design Guide, V2.1
5.8 AC Line Transient Specification
STATUS
Recommended
AC line transient conditions shall be defined as “sag” and “surge” conditions. Sag conditions (also referred to as
“brownout” conditions) will be defined as the AC line voltage dropping below nominal voltage. Surge will be
defined as the AC line voltage rising above nominal voltage.
The power supply shall meet the requirements under the following AC line sag and surge conditions.
Table 5: AC Line Sag Transient Performance
Duration Sag Operating AC Voltage Line Frequency Performance Criteria
Continuous 10% Nominal AC Voltage ranges 50/60 Hz No loss of function or performance
0 to 1 AC cycle 100% Nominal AC Voltage ranges 50/60 Hz No loss of function or performance
> 1 AC cycle >10% Nominal AC Voltage ranges 50/60 Hz Loss of function acceptable, self-
recoverable
Table 6: AC Line Surge Transient Performance
Duration Surge Operating AC Voltage Line Frequency Performance Criteria
Continuous 10% Nominal AC Voltages 50/60 Hz No loss of function or performance
0 to ½ AC cycle 30% Mid-point of nominal AC
Voltages
50/60 Hz No loss of function or performance
5.9 AC Line Fast Transient Specification
STATUS
Recommended
The power supply shall meet the EN61000-4-5 directive and any additional requirements in IEC1000-4-5:1995
and the Level 3 requirements for surge-withstand capability, with the following conditions and exceptions:
• These input transients must not cause any out-of-regulation conditions, such as overshoot and
undershoot, nor must it cause any nuisance trips of any of the power supply protection circuits.
• The surge-withstand test must not produce damage to the power supply.
• The supply must meet surge-withstand test conditions under maximum and minimum DC-output load
conditions.
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EPS1U Power Supply Design Guide, V2.1
6 DC Output Specification
6.1 Connector
STATUS
Required
6.1.1 Power Connector (125W, 250W, 350W, 400W)
The power supply uses a blind mating type connector with edge fingers (see Figure 1) to connect the power
supply’s output voltages and signals to a connector located in the system. The card edge pin assignments are
listed in Table 7. Figure 3 shows the card edge layout for the power supply. The connector located in the system
is an AMP 1364999-1 or equivalent.
Signals that can be defined as low true or high true use the following convention: signal
pins are reserved for future use.
The higher power level version of the power supply uses the same connector type but a different pin assignment
and keying. The card edge pin assignments are listed in Table 7. Figure 3 shows the card edge layout for the
high power supply. The connector located in the system is an AMP 1364999-1 or equivalent.
Signals that can be defined as low true or high true use the following convention: signal
pins are reserved for future use.
The ground of the pins of the power supply wire harness provides the power return path. The wire harness
ground pins shall be connected to safety ground (power supply enclosure).
6.3 Remote Sense
STATUS
Optional
The power supply may have remote sense return (ReturnS) to regulate out ground drops for all output voltages;
+3.3 V, +5 V, +12 V1, +12 V2, -12 V, and 5 VSB. The power supply may use remote sense (3.3VS) to regulate
out drops in the system for the +3.3 V output. The +5 V, +12 V1, +12 V2, –12 V, and 5 VSB outputs only use
remote sense referenced to the ReturnS signal. The remote sense input impedance to the power supply must be
greater than 200 Ω on 3.3 VS and ReturnS. This is the value of the resistor connecting the remote sense to the
output voltage internal to the power supply. Remote sense must be able to regulate out a minimum of 200 mV
drop on the +3.3 V output. The remote sense return (ReturnS) must be able to regulate out a minimum of 200 mV
drop in the power ground return. The current in any remote sense line shall be less than 5 mA to prevent voltage
sensing errors. The power supply must operate within specification over the full range of voltage drops from the
power supply’s output connector to the remote sense points.
6.4 Output Power/Currents
STATUS
Recommendations
The following tables define power and current ratings for 125 W to 500 W power supplies. These output levels
were selected to cover different types of systems and configurations. The combined output power of all outputs
shall not exceed the rated output power. The tables show the load ranges for each of the power supply power
levels. The power supply must meet both static and dynamic voltage regulation requirements for the minimum
loading conditions.
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EPS1U Power Supply Design Guide, V2.1
Table 9: 125 W Load Ratings
Load Range
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 6 A
+5 V 0.5 A 12 A
+12 V1 0.25 A 3 A 6 A
+12 V2 Not used for 125W version.
-12 V 0 A 0.2 A
+5 VSB 0.1 A 1.0 A
1. Maximum continuous total DC output power should not exceed 125 W.
2. Peak total DC output power should not exceed 161 W.
3. Peak power and current loading shall be supported for a minimum of 12 seconds.
Table 10: 250 W Load Ratings
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 16 A
+5 V 0.5 A 12 A
+12 V1 0.2 A 16 A See note 2
+12 V2 0.5 A 10 A See note 2
-12 V 0 A 0.5 A
+5 VSB 0.1 A 2.0 A
1. Maximum continuous total DC output power should not exceed 250 W.
2. Peak load on the combined 12 V output shall not exceed 22 A.
3. Maximum continuous load on the combined 12 V output shall not exceed 18 A.
4. Peak total DC output power should not exceed 300 W.
5. Peak power and current loading shall be supported for a minimum of 12 seconds.
Table 11: 350 W Load Ratings
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 16 A
+5 V 0.5 A 12 A
+12 V1 0.2 A 18 A 22 A 6
+12 V2 0.5 A 16 A
-12 V 0 A 0.5 A
+5 VSB 0.1 A 2.0 A
1. Maximum continuous total DC output power should not exceed 350 W.
2. Peak load on the combined 12 V output shall not exceed 32 A.
3. Maximum continuous load on the combined 12 V output shall not exceed 28 A.
4. Peak total DC output power should not exceed 400 W.
5. Peak power shall be supported for a minimum of 12 seconds.
6. Peak +12 V1 current shall be supported for a minimum of 0.5 seconds.
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EPS1U Power Supply Design Guide, V2.1
Table 12: 400 W Load Ratings
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 16 A
+5 V 0.5 A 12 A
+12 V1 0.2 A 18 A 22 A 7
+12 V2 0.5 A 16 A
-12 V 0 A 0.5 A
+5 VSB 0.1 A 2.0 A
1. Maximum continuous total DC output power should not exceed 400 W.
2. Peak load on the combined 12 V output shall not exceed 34 A.
3. Maximum continuous load on the combined 12 V output shall not exceed 30 A.
4. Peak total DC output power should not exceed 450 W.
5. Peak power and current loading shall be supported for a minimum of 12 seconds.
6. Combined 3.3V and 5V power shall not exceed 90W.
7. Peak +12 V1 current shall be supported for a minimum of 0.5 seconds.
Table 13: 450 W Load Ratings
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 16 A
+5 V 0.5 A 12 A
+12 V1 0.2 A 11 A 13 A
+12 V2 0.2 A 11 A 13 A
+12 V3 0.5 A 15 A 18 A
-12 V 0 A 0.5 A
+5 VSB 0.1 A 2.0 A
1. Maximum continuous total DC output power should not exceed 450 W.
2. Peak load on the combined 12 V output shall not exceed 40 A.
3. Maximum continuous load on the combined 12 V output shall not exceed 35 A.
4. Peak total DC output power should not exceed 500 W.
5. Peak power and current loading shall be supported for a minimum of 12 seconds.
6. Combined 3.3V and 5V power shall not exceed 90W.
Table 14: 500 W Load Ratings
Voltage Minimum Continuous Maximum Continuous Peak
+3.3 V 0.5 A 16 A
+5 V 0.5 A 12 A
+12 V1 0.2 A 12.5 A 15 A
+12 V2 0.2 A 12.5 A 15 A
+12 V3 0.5 A 18 A 22 A 8
-12 V 0 A 0.5 A
+5 VSB 0.1 A 2.0 A
1. Maximum continuous total DC output power should not exceed 500 W.
2. Peak load on the combined 12 V output shall not exceed 46 A.
3. Maximum continuous load on the combined 12 V output shall not exceed 39 A.
4. Peak total DC output power should not exceed 590 W.
5. Peak power and current loading shall be supported for a minimum of 12 seconds.
6. Combined 3.3V and 5V power shall not exceed 90W.
8. Peak +12 V3 current shall be supported for a minimum of 0.5 seconds.
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EPS1U Power Supply Design Guide, V2.1
6.4.1 Standby Outputs
STATUS
Required
The 5 VSB output shall be present when an AC input greater than the power supply turn on voltage is applied.
6.5 Voltage Regulation
STATUS
Required
The power supply output voltages must stay within the following voltage limits when operating at steady state and
dynamic loading conditions. These limits include the peak-peak ripple/noise specified in Section 6.8. All outputs
are measured with reference to the return remote sense (ReturnS) signal. The 5 V, 12 V1, 12 V2, –12 V and 5
VSB outputs are measured at the power supply connectors referenced to ReturnS. The +3.3 V is measured at its
remote sense signal (3.3 VS) located at the signal connector.
Table 15: Voltage Regulation Limits
Parameter MIN NOM MAX Units Tolerance
+3.3 V +3.20 +3.30 +3.46 V
+5 V +4.80 +5.00 +5.25 V
+12 V1 +11.52 +12.00 +12.60 V
+12 V2 +11.52 +12.00 +12.60 V
+5/-3%
rms
+5/-4%
rms
+5/-4%
rms
+5/-4%
rms
-12 V -11.40 -12.20 -13.08 V
+5 VSB +4.85 +5.00 +5.25 V
+9/-5%
rms
+5/-3%
rms
STATUS
Optional
Some system applications may require tighter regulation limits on the +5 V output. The optional regulation limits
are shown below.
Table 16: Optional +5V Regulation Limits
Parameter MIN NOM MAX Units Tolerance
+5 V +4.85 +5.00 +5.25 V
+5/-3%
rms
6.6 Dynamic Loading
STATUS
Required
The output voltages shall remain within the limits specified in Table 15 for the step loading and within the limits
specified in Table 17 for the capacitive loading. The load transient repetition rate shall be tested between 50 Hz
and 5 kHz at duty cycles ranging from 10%-90%. The load transient repetition rate is only a test specification.
The ∆ step load may occur anywhere within the MIN load to the MAX load shown in Table 10, Table 11, Table 12,
Table 13, or Table 14.
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EPS1U Power Supply Design Guide, V2.1
Table 17: Transient Load Requirements
Output
+3.3 V 30% of max load
+5 V 30% of max load
12 V1, 12V2, 12V3 65% of max load
+5 VSB 25% of max load
∆ Step Load Size
6.7 Capacitive Loading
STATUS
Required
The power supply shall be stable and meet all requirements with the following capacitive loading ranges.
Table 18: Capacitive Loading Conditions
Output MIN MAX Units
+3.3 V 10 6,800
+5 V 10 4,700
+12 V 10 11,000
-12 V 1 350
+5 VSB 1 350
Load Slew Rate Capacitive Load
0.5 A/µs 1000 µF
0.5 A/µs 1000 µF
0.5 A/µs 2200 µF
0.5 A/µs 1 µF
µF
µF
µF
µF
µF
6.8 Ripple / Noise
STATUS
Required
The maximum allowed ripple/noise output of the power supply is defined in Table 19 below. This is measured
over a bandwidth of 0 Hz to 20 MHz at the power supply output connectors. A 10 µF tantalum capacitor in
parallel with a 0.1 µF ceramic capacitor are placed at the point of measurement.
Table 19: Ripple and Noise
+3.3 V +5 V +12 V -12 V +5 VSB
50 mVp-p 50 mVp-p 120 mVp-p 120 mVp-p 50 mVp-p
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EPS1U Power Supply Design Guide, V2.1
6.9 Timing Requirements
STATUS
Required
These are the timing requirements for the power supply operation. The output voltages must rise from 10% to
within regulation limits (T
rise at about the same time. All outputs must rise monotonically. The +5 V output needs to be greater than the
+3.3 V output during any point of the voltage rise. The +5 V output must never be greater than the +3.3V output
by more than 2.25 V. Each output voltage shall reach regulation within 50 ms (T
on of the power supply. Each output voltage shall fall out of regulation within 400 ms (T
during turn off. Figure 5 and Figure 6 show the turn ON and turn OFF timing requirements. In Figure 6 the timing
is shown with both AC and PSON# controlling the ON/OFF of the power supply.
Item Description MIN MAX Units
T
T
T
Output voltage rise time from each main output. 5 70 ms
vout_rise
All main outputs must be within regulation of each
vout_on
All main outputs must leave regulation within this
vout_off
other within this time.
time.
Vout
V1
10%
Vout
V2
V3
) within 5 to 70 ms. The +3.3 V, +5 V and +12 V output voltages should start to
vout_rise
) of each other during turn
vout_on
) of each other
vout_off
Table 20: Output Voltage Timing
50 ms
400 ms
T
T
vout rise
T
vout on
vout_off
Figure 5: Output Voltage Timing
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EPS1U Power Supply Design Guide, V2.1
Table 21: Turn On/Off Timing
Item Description MIN MAX Units
Tsb_on_delay Delay from AC being applied to 5 VSB being
within regulation.
T ac_on_delay Delay from AC being applied to all output
voltages being within regulation.
Tvout_holdup Time all output voltages stay within regulation
after loss of AC.
Tpwok_holdup Delay from loss of AC to deassertion of PWOK 17 ms
Tpson_on_delay Delay from PSON# active to output voltages
within regulation limits.
T pson_pwok Delay from PSON# deactive to PWOK being
deasserted.
Tpwok_on Delay from output voltages within regulation
limits to PWOK asserted at turn on.
T pwok_off Delay from PWOK deasserted to output
voltages (3.3 V, 5 V, 12 V, -12 V) dropping out
of regulation limits.
Tpwok_low Duration of PWOK being in the deasserted state
during an off/on cycle using AC or the PSON#
signal.
Tsb_vout Delay from 5 VSB being in regulation to O/Ps
being in regulation at AC turn on.
1500 ms
2500 ms
18 ms
5 400 ms
50 ms
100 1000 ms
1 ms
100 ms
50 1000 ms
STATUS
Recommended
Item Description MIN MAX UNITS
T
vout_holdup
T
pwok_holdup
T
sb_holdup
Time all output voltages stay within regulation
after loss of AC.
Delay from loss of AC to deassertion of PWOK. 20 ms
Time 5VSB output voltage stays within regulation
after loss of AC.
21 ms
70 ms
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A
A
EPS1U Power Supply Design Guide, V2.1
C Input
Vout
T
vout_holdup
T
PWOK
5VSB
sb_on_delay
T
AC_on_delay
T
sb_vout
C turn on/off cycle
T
pwok_low
T
T
pwok_on
T
pwok_holdup
pwok_off
Tsb_holdup
T
sb_on_delay
T
pson_on_delay
PSON turn on/off cycle
Figure 6: Turn On/Off Timing (Signal Power Supply)
T
pwok_on
T
T
pson_pwok
pwok_off
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EPS1U Power Supply Design Guide, V2.1
7 Protection Circuits
STATUS
Required
Protection circuits inside the power supply shall cause only the power supply’s main outputs to shutdown. If the
power supply latches off due to a protection circuit tripping, an AC cycle OFF for 15 seconds and a PSON# cycle
HIGH for 1 second shall be able to reset the power supply.
7.1 Current Limit
STATUS
Required
The power supply shall have current limit to prevent the +3.3 V, +5 V, and +12 V outputs from exceeding the
values shown in Table 22. If the current limits are exceeded, the power supply shall shutdown and latch off. The
latch will be cleared by toggling the PSON
damaged from repeated power cycling in this condition. –12 V and 5 VSB shall be protected under over current
or shorted conditions so that no damage can occur to the power supply. All outputs shall be protected so that no
damage occurs to the power supply under a shorted output condition.
#
signal or by an AC power interruption. The power supply shall not be
Table 22: Over Current Protection
Voltage Over Current Limit (Iout limit)
+3.3 V 110% minimum; 150% maximum
+5 V 110% minimum; 150% maximum
+12 V 110% minimum; 150% maximum
7.2 240VA Protection
STATUS
Recommended
System designs may require user access to energized areas of the system. In these cases the power supply may
be required to meet regulatory 240VA limits for any power rail. Since the +12V rail combined power exceeds
240VA it must be divided into separate channels to meet this requirement. Each separate rail needs to be limited
to less than 20A for each +12V rail. The separate +12V rails do not necessarily need to be independently
regulated outputs. They can share a common power conversion stage. The +12V rail is divided into two rails for
the 250W, 350W, and 400W power levels. +12V1 is dedicated for providing power to the input of the processor
voltage regulator(s). +12V2 is used to power the rest of the baseboard’s +12V power needs and system
peripheral devices. The +12V rail is divided into three rails for the 450W and 500W power levels. The +12V1 and
+12V2 rails are dedicated for providing power to the inputs of the processor voltage regulators. The +12V3 rail is
used to power the rest of the baseboard’s +12V power needs and system peripheral devices.
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EPS1U Power Supply Design Guide, V2.1
Table 23: Over Current Protection
250W – 400W 450W – 500W
Voltage Over Current Limit (Iout limit) Over Current Limit (Iout limit)
+3.3 V 110% minimum; 150% maximum 110% minimum; 150% maximum
+5 V 110% minimum; 150% maximum 110% minimum; 150% maximum
+12V1 18A minimum; 20A maximum; 22A peak1 Peak current minimum; 20A maximum
+12V2 Peak current minimum; 20A maximum Peak current minimum; 20A maximum
+12V3 N/A 18A minimum; 20A maximum; 22A peak 1
1. Peak currents shall be maintained for a minimum of 500msec. The maximum duration of the peak
current exceeding the 240VA limit should be limited to meet safety regulations. A maximum duration
of 1 second is recommended.
7.3 Over Voltage Protection
STATUS
Required
The power supply over voltage protection shall be locally sensed. The power supply shall shutdown and latch off
after an over voltage condition occurs. This latch shall be cleared by toggling the PSON# signal or by an AC
power interruption. Table 24 contains the over voltage limits. The values are measured at the output of the
power supply’s connectors. The voltage shall never exceed the maximum levels when measured at the power
pins of the power supply connector during any single point of fail. The voltage shall never trip any lower than the
minimum levels when measured at the power pins of the power supply connector.
Table 24: Over Voltage Limits
Output Voltage MIN (V) MAX (V)
+3.3 V 3.9 4.5
+5 V 5.7 6.5
+12 V1, 2 13.3 14.5
-12 V -13.3 -14.5
+5 VSB 5.7 6.5
7.4 Over Temperature Protection
STATUS
Recommended
The power supply will be protected against over temperature conditions caused by loss of fan cooling or
excessive ambient temperature. In an OTP condition the PSU will shutdown. When the power supply
temperature drops to within specified limits, the power supply shall restore power automatically. The OTP circuit
must have built in hysteresis such that the power supply will not oscillate on and off due to temperature recovering
condition. The OTP trip level shall have a minimum of 4 °C of ambient temperature hysteresis.
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EPS1U Power Supply Design Guide, V2.1
8 Control and Indicator Functions
The following sections define the input and output signals from the power supply.
Signals that can be defined as low true use the following convention:
#
signal
8.1 PSON#
The PSON# signal is required to remotely turn on/off the power supply. PSON# is an active low signal that turns
on the +3.3 V, +5 V, +12 V, and –12 V power rails. When this signal is not pulled low by the system, or left open,
the outputs (except the +5 VSB and Vbias) turn off. This signal is pulled to a standby voltage by a pull-up resistor
internal to the power supply. Refer to Figure 6 for the timing diagram.
= low true
STATUS
Required
Table 25: PSON# Signal Characteristic
Signal Type
PSON# = Low
PSON# = Open or High
Logic level low (power supply ON)
Logic level high (power supply OFF)
Source current, Vpson = low
Power up delay: T
PWOK delay: T
pson_pwok
pson_on_delay
Accepts an open collector/drain input from the system.
Pull-up to VSB located in power supply.
ON
OFF
MIN MAX
0 V 1.0 V
2.0 V 5.25 V
4 mA
5 ms 400 ms
50 ms
Disabled
Hysteresis ≥ 0.3V and/or other de-bounce method
≤ 1.0 V
PS must
be
enabled
≥ 2.0 V
PS must
be
disabled
Enabled
0V
1.0V
2.0V
5.25V
Figure 7: PSON# Signal Characteristics
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EPS1U Power Supply Design Guide, V2.1
8.2 PWOK (Power OK)
STATUS
Required
PWOK is a power OK signal and will be pulled HIGH by the power supply to indicate that all the outputs are within
the regulation limits of the power supply. When any output voltage falls below regulation limits or when AC power
has been removed for a time sufficiently long so that power supply operation is no longer guaranteed, PWOK will
be de-asserted to a LOW state. See Figure 6 for a representation of the timing characteristics of PWOK. The
start of the PWOK delay time shall be inhibited as long as any power supply output is in current limit.
Table 26: PWOK Signal Characteristics
Signal Type
+5V TTL Compatible output signal
PWOK = High
PWOK = Low
Logic level low, Isink = 4mA
Logic level high, Isource = 200µA
PWOK delay: T
PWOK rise and fall time
Power down delay: T
pwok_on
pwok_off
Power OK
Power not OK
MIN MAX
0.4 V
2.4 V 5.25 V
200 ms 1000 ms
1 ms
100 µs
8.3 AC Warning
STATUS
Optional
This is an output signal from the power supply, which provides a warning to the system that the power supply has
lost its AC input. This signal also provides a signal to synchronize the turn on of multiple power supplies. At turn
on, this signal is pulled LOW when the supply’s internal bulk voltage has reached a level that allows it to turn on.
At turn off ACWarning goes HIGH when the internal bulk voltage drops low enough. The characteristics of the
ACWarning signal are shown in Table 27: ACWarning Signal Characteristics
diagram.
Table 27: ACWarning Signal Characteristics
Signal Type
ACWarning = Low
ACWarning = High
MIN MAX
Logic level low, Isink = 4mA
Logic level high, Isource = 200µA
ACWarning Delay: T
ACWarning rise and fall time
Power supply turn on voltage
acwarning_delay
8msec
+5V TTL Compatible output signal
Input voltage within operating range and power
supply is ready to turn on.
Input voltage is less than the operating range and the
power supply is turning off.
0V 0.4V
2.4 V 5.25V
75VAC 85VAC
. Refer to Figure 6 for timing
100µsec
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EPS1U Power Supply Design Guide, V2.1
8.4 Field Replacement Unit (FRU) Signals
STATUS
Optional
Two pins will be allocated for the FRU information on the power supply connector. One pin is the Serial Clock
(SCL). The second pin is used for Serial Data (SDA). Both pins are bi-directional and are used to form a serial
bus. The FRU circuits inside the power supply must be powered off of 5 VSB output and grounded to ReturnS
(remote sense return). The Write Control (or Write protect) pin should be tied to ReturnS inside the power supply
so that information can be written to the EEPROM.
8.4.1 FRU Data
FRU data shall be stored starting in address location 8000h through 80FFh. The FRU data format shall be
compliant with the IPMI specifications. The current version of these specifications is available at
The information to be contained in the FRU device is shown in the following table.
Table 28: FRU Device Information
Area Type Description
Common Header As defined by the FRU document
Internal Use Area Not required, do not reserve
Chassis Info Area Not applicable, do not reserve
Board Info Area Not applicable, do not reserve
.
8.4.2.1 Product Info Area
Implement as defined by the IPMI FRU document. Product information shall be defined as follows:
Table 29: FRU Device Product Information Area
Field Name Field Description
Manufacturer Name {Formal name of manufacturer}
Product Name {Manufacturer’s model number}
Product part/model
number
Product Version Customer current revision
Product Serial Number {Defined at time of manufacture}
Asset Tag {Not used, code is zero length byte}
FRU File ID {Not required}
PAD Bytes {Added as necessary to allow for 8-byte offset to next area}
Customer part number
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EPS1U Power Supply Design Guide, V2.1
8.4.2.2 MultiRecord Area
Implement as defined by the IPMI FRU document. The following record types shall be used on this power supply:
• Power Supply Information (Record Type 0x00)
• DC Output (Record Type 0x01)
• No other record types are required for the power supply.
MultiRecord information shall be defined as follows:
Table 30: FRU Device MultiRecord Area
Field Name (PS Info) Field Information Definition
Overall Capacity (W) 350 {Low power versions would be 250 or 125}
Peak VA 400 {Low power versions would be 300 or 161}
Inrush current (A) 30
Inrush interval (ms) 5
Low end input voltage
range 1
High end input voltage
range 1
Low end input voltage
range 2
High end input voltage
range 2
A/C dropout tol. (ms) 20
Binary flags Set for: Not Hot Swap support, Auto-switch, and PFC
Peak Wattage Set for: 12 s, 400 W {Low power versions would be 300W or 161W}
Combined wattage Set for 5 V & 3.3 V combined wattage of 113 W {Low power versions would be 113W
Predictive fail tach
support
Field Name (Output) Field Description: Six outputs are to be defined from #1 to #6, as follows: +3.3 V, +5
Output Information Set for: Standby on +5 VSB, No Standby on all others.
All other output fields Format per IPMI specification, using parameters in the EPS1U specification.
90
140
180
264
or 80}
Not supported, 00h value
V, +12 V1, +12V2, -12 V, and +5 VSB.
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EPS1U Power Supply Design Guide, V2.1
8.5 LED Indicator
STATUS
Required
There will be a single GREEN LED to indicate power supply status. When AC is applied to the PSU and standby
voltages are available the LED shall BLINK GREEN. The LED shall turn ON GREEN to indicate that all the power
outputs are available. Refer to Table 31 for conditions of the LED.
Table 31: LED Indicators
Power Supply Condition Power Supply LED
No AC power to PSU or PSU failure OFF
AC present / Only Standby Output ON BLINK GREEN
Power supply DC outputs ON and OK GREEN
The LED shall be visible on the power supply’s exterior face. The LED location shall meet ESD requirements.
LED shall be securely mounted in such a way that incidental pressure on the LED shall not cause it to become
displaced.
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EPS1U Power Supply Design Guide, V2.1
9 MTBF
STATUS
Recommended
The power supply shall have a minimum MTBF at continuous operation of 1) 100,000 hours at 100% load and
45
° C, as calculated by Bellcore RPP, or 2) 250,000 hours demonstrated at 100% load and 45° C.
10 Agency Requirements
STATUS
Recommended
The power supply must comply with all regulatory requirements for its intended geographical market. Depending
on the chosen market, regulatory requirements may vary. Although a power supply can be designed for
worldwide compliance, there may be cost factors that drive different versions of supplies for different
geographically targeted markets.
This specification requires that the power supply meet all regulatory requirements for the intended market at the
time of manufacturing. Typically this includes:
• UL
• CSA
• A Nordic CENELEC
• TUV
• VDE
• CISPR Class B
• FCC Class B
The power supply, when installed in the system, shall meet immunity requirements specified in EN55024.
Specific tests are to be EN61000-4-2, -3, -4, -5, -6, -8, and -11. The power supply must maintain normal
performance within specified limits. This testing must be completed by the system EMI engineer. Conformance
must be designated with the European Union CE Marking. Specific immunity level requirements are left to
customer requirements.
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