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TFX12V
Thin Form Factor with 12-Volt Connector
Power Supply Design Guide
Version 1.2
Revision History
Version Release Date
Notes
1.0
Apr, 2002
•
Public release
1.01
May, 2002
•
Added dimension in Figure 5 to clarify location of mounting slot
feature
1.2
April, 2003
•
Updated power and current guidance
•
Added efficiency targets for light and nominal loading
•
Increased minimum Efficiency at full load from 68% to 70%
•
Updated guidance for standby efficiency
•
Added Serial ATA connector
•
Updated Revision his tory table
•
Reformat title page
•
Added cross loading tables
•
Added loading tables for efficiency measurement points
•
Minor modifications to Energy Star
TFX12V Power Supply Design Guide
Version 1.2
IMPORTANT INFORMATION AND DISCLAIMERS
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NO LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL
PROPERTY RIGHTS IS GRANTED HEREIN.
Intel and Pentium are registered trademarks of Intel Corporation or its subsidiaries in the United States and
other countries.
Copyright  2002, 2003 Intel Corporation. All rights reserved.
* Other names and brands may be claimed as the property of others.
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TFX12V Power Supply Design Guide
Version 1.2
Contents
1 Introduction .................................................................................................. 6
1.1
1.2
TFX12V Scope ..................................................................................................................6
TFX12V Overview .............................................................................................................6
1.2.1
Small System Optimized Profile........................................................................6
1.2.2
Improved Acoustics............................................................................................7
1.2.3
Efficiency............................................................................................................7
1.2.4
Increased Power ................................................................................................7
2 Electrical....................................................................................................... 7
2.1
2.2
2.3
2.4
AC Output..........................................................................................................................7
2.1.1
Input Over Current Protection ............................................................................8
2.1.2
Inrush Current Limiting.......................................................................................8
2.1.3
Input Under Voltage ............................................................................................8
2.1.4
Regulatory..........................................................................................................8
2.1.5
Catastrophic Failure Protection .........................................................................8
DC Output .........................................................................................................................9
2.2.1
DC Voltage Regulation.......................................................................................9
2.2.2
Remote Sensing ................................................................................................9
2.2.3
Typical Power Distribution ...............................................................................10
2.2.4
Power Limit / Hazardous Energy Levels..........................................................14
2.2.5
Efficiency General ............................................................................................15
2.2.6
Output Ripple/Noise.........................................................................................16
2.2.7
Output Transient Response.............................................................................17
2.2.8
Capacitive Load................................................................................................18
2.2.9
Closed-loop Stability.........................................................................................18
2.2.10 +5 VDC / +3.3 VDC Power Sequencing..........................................................18
2.2.11 Voltage Hold-up Time.......................................................................................18
Timing / Housekeeping / Control.....................................................................................19
2.3.1
PWR_OK .........................................................................................................19
2.3.2
PS_ON# ...........................................................................................................20
2.3.3
+5 VSB .............................................................................................................21
2.3.4
Power-on Time.................................................................................................21
2.3.5
Rise Time.........................................................................................................21
2.3.6
Overshoot at Turn-on / Turn-off .......................................................................21
2.3.7
Reset after Shutdown ......................................................................................21
2.3.8
+5 VSB at AC Power-down..............................................................................22
Output Protection ............................................................................................................22
2.4.1
Over Voltage Protection ...................................................................................22
2.4.2
Short-circuit Protection ....................................................................................22
2.4.3
No-load Operation ............................................................................................22
2.4.4
Over Current Protection...................................................................................22
2.4.5
Over-temperature Protection ...........................................................................23
2.4.6
Output Bypass .................................................................................................23
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TFX12V Power Supply Design Guide
Version 1.2
3 Mechanical .................................................................................................. 23
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Labeling /Marking.............................................................................................................23
Physical Dimensions ......................................................................................................23
Mounting Options ............................................................................................................26
Chassis Requirements ...................................................................................................27
Airflow / Fan.....................................................................................................................28
AC Connector..................................................................................................................28
DC Connectors ...............................................................................................................29
3.7.1
TFX12V Main Power Connector.......................................................................30
3.7.2
Peripheral Connector(s)...................................................................................30
3.7.3
Floppy Drive Connector ...................................................................................30
3.7.4
+12 V Power Connector...................................................................................31
3.7.5
Serial ATA Power Connector ...........................................................................31
4 Environmental............................................................................................. 32
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Temperature....................................................................................................................32
Thermal Shock (Shipping) ..............................................................................................32
Relative Humidity.............................................................................................................32
Altitude Requirement.......................................................................................................32
Mechanical Shock...........................................................................................................32
Random Vibration............................................................................................................33
Acoustics.........................................................................................................................33
Ecological Requirements ................................................................................................33
5 Safety.......................................................................................................... 34
5.1
5.2
North America .................................................................................................................34
International .....................................................................................................................34
6 Electromagnetic Compatibility..................................................................... 35
6.1
6.2
6.3
6.4
6.5
Emissions .......................................................................................................................35
Immunity..........................................................................................................................35
Input Line Current Harmonic Content .............................................................................36
Magnetic Leakage Fields.................................................................................................36
Voltage Fluctuations and Flicker .....................................................................................36
7 System Cooling Considerations.................................................................. 37
8 Reliability .................................................................................................... 37
9 Applicable Documents................................................................................. 37
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TFX12V Power Supply Design Guide
Version 1.2
Figures
Figure 1. TFX12V Power Supply.....................................................................................................6
Figure 2. Cross loading Graph for 180W configuration ................................................................11
Figure 3. Cross loading Graph for 220W configuration ................................................................12
Figure 4. Cross loading Graph for 240W configuration ................................................................13
Figure 5. Differential Noise Test Setup .........................................................................................17
Figure 6. Power Supply Timing.....................................................................................................19
Figure 7. PS_ON# Signal Characteristics ....................................................................................20
Figure 8. Power Supply Dimensions and Recommended Feature Placements (not to scale)...24
Figure 9. Power Supply Mounting Slot Detail................................................................................25
Figure 10. Fan Right and Fan Left Orientations of Power Supply in a Chassis ...........................26
Figure 11. Suggested TFX12V Chassis Cutout............................................................................27
Figure 12. Suggested Mounting Tab (chassis feature).................................................................27
Figure 13. TFX12V Connectors (Pin-side view, not to scale).......................................................29
Figure 14. Serial ATA connector ....................................................................................................31
Tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
AC Input Line Requirements ..............................................................................7
DC Output Voltage Regulation...........................................................................9
Typical Power Distribution for 180 W TFX12V Configurations ........................11
Typical Power Distribution for 220 W TFX12V Configurations ........................11
Typical Power Distribution for 240 W TFX12V Configurations ........................13
Efficiency Vs Load............................................................................................15
Loading table for Efficiency measurements ....................................................15
Energy Star Input Power Consumption ...........................................................16
DC Output Noise/Ripple...................................................................................16
DC Output Transient Step Sizes .....................................................................17
Output Capacitive Loads..................................................................................18
PWR_OK Signal Characteristics ....................................................................19
PS_ON# Signal Characteristics ......................................................................20
Over Voltage Protection ...................................................................................22
Harmonic Limits, Class D Equipment .............................................................36
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TFX12V Power Supply Design Guide
Version 1.2
1 Introduction
1.1 TFX12V Scope
This document provides design suggestions for a small form factor power supply that is primarily intended
for use with small form factor system designs (9-15 liters in total system volume). It should not be inferred
that all Thin Form Factor 12 Volt (TFX12V) 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.
Figure 1. TFX12V Power Supply
1.2 TFX12V Overview
This section provides a brief overview of the unique features of the TFX12V power supply design and a
summary of the changes included in revision 1.2.
1.2.1 Small System Optimized Profile
The increase in demand for smaller systems results in unique system layout challenges. The TFX12V
configuration has been optimized for small and low profile microATX and FlexATX system layouts. The long
narrow profile of the power supply (shown in Figure 1) fits easily into low profile systems. The fan
placement can be used to efficiently exhaust air from the processor and core area of the motherboard,
making possible smaller, more efficient systems using common industry ingredients.
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TFX12V Power Supply Design Guide
Version 1.2
1.2.2 Improved Acoustics
As desktop systems become smaller, they are placed in more exposed areas in the home and work place.
The smaller systems are no longer confined to the floor or under the desk, but are placed on the desktop
next to the user. In these situations, noise becomes an important factor to the end user. TFX12V supplies
should use fan speed control techniques to provide a low acoustic profile, while providing ample cooling to
internal components when required.
1.2.3 Efficiency
Updated guidance for standby efficiency, raised max load eff to 70%, and added 50% and 20% loading
criteria
1.2.4 Increased Power
The trend for faster and more powerful systems results in an increasing need for higher rated power
supplies. Additional power ratings have been added with increased 5 VDC and 12 VDC current to meet the
needs of present and future system needs. Power ratings have been added at 240 W. These have been
added for guidance and are not intended to limit the choice of power ratings available.
2 Electrical
The following electrical requirements must be met over the environmental ranges as defined in Section 5
(unless otherwise noted).
2.1 AC Output
Table 1, 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 switchselectable or auto-ranging. The power supply shall automatically recover from AC power loss. The power
supply must be able to start up under peak loading at 90 VAC.
Table 1.
AC Input Line Requirements
Parameter
Minimum
Nominal*
Maximum
Unit
Vin (115 VAC)
90
115
135
VAC
Vin (230 VAC)
180
230
265
VAC rms
Vin Frequency
47
--
63
Hz
rms
*Note: Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.
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TFX12V Power Supply Design Guide
Version 1.2
2.1.1 Input Over Current Protection
The power supply shall 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.1
2.1.2 Inrush Current Limiting
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 input line cord, AC switch
if present, bridge rectifier, fuse, and EMI filter components. Repetitive ON/OFF cycling of the AC input voltage
should not damage the power supply or cause the input fuse to blow.
2.1.3 Input Under Voltage
The power supply shall contain protection circuitry such that the application of an input voltage below the
minimum specified in Section 2.1, Table 1, shall not cause damage to the power supply.
2.1.4 Regulatory
At a minimum, both system and power supply typically must pass safety and EMC testing per the limits and
methods described in the EN 55024 Specification prior to sale in most parts of the world. Additional
national requirements may apply depending on the design, product end use, target geography, customer,
and other variables. Consult your company’s Product Safety and Regulations department for more details.
2.1.5 Catastrophic Failure Protection
Should a component failure o ccur, the power supply should not exhibit any of the following:
•
•
•
•
•
•
•
1
8
Flame
Excessive smoke
Charred PCB
Fused PCB conductor
Startling noise
Emission of molten material
Earth ground fault (short circuit to ground or chassis enclosure)
For Denmark and Switzerland international safety requirements, if the internal over current protective devices exceed
8A for Denmark and 10A for Switzerland, then the power supply must pass international safety testing to EN 60950
using a maximum 16A over-current protected branch circuit, and this 16A (time delay fuse) branch circuit protector
must not open during power supply abnormal operation (output short circuit and component fault) testing.
TFX12V Power Supply Design Guide
Version 1.2
2.2 DC Output
2.2.1 DC Voltage Regulation
The DC output voltages shall remain within the regulation ranges shown in Table 2, when measured at the
load end of the output connectors under all line, load, and environmental conditions. The voltage regulation
limits shall be maintained under continuous operation for any steady state temperature and operating
conditions specified in Section 4.
Table 2.
DC Output Voltage Regulation
Output
Range
Minimum
Nominal
Maximum
Unit
+12 VDC (Note)
±5%
+11.40
+12.00
+12.60
Volts
+5 VDC
±5%
+4.75
+5.00
+5.25
Volts
+3.3 VDC
±5%
+3.14
+3.30
+3.47
Volts
-12 VDC
±10%
-10.80
-12.00
-13.20
Volts
+5 VSB
±5%
+4.75
+5.00
+5.25
Volts
Note: At +12 VDC peak loading, regulation at the +12 VDC output can go to ± 10%.
2.2.2 Remote Sensing
The +3.3 VDC output should have provisions for remote sensing to compensate for excessive cable drops.
The default sense should be connected to pin 11 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.
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TFX12V Power Supply Design Guide
Version 1.2
2.2.3 Typical Power Distribution
DC output power requirements and distributions will vary based on specific system options and
implementation.
Significant dependencies include the quantity and types of processors, memory, add-in card slots, and
peripheral bays, as well as support for advanced graphics or other features. Tables 3, through
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TFX12V Power Supply Design Guide
Version 1.2
Table 5 show the power distribution and cross loading tables for power supplies in the range of 180 W to
240 W. It is ultimately the responsibility of the designer to define a power budget for a given target product
and market.
Table 3.
Typical Power Distribution for 180 W TFX12V Configurations
Output
Minimum
Current (amps)
Rated Current
(amps)
Peak Current
(amps)
+12 VDC
1.0
13.0
15.0
+5 VDC
0.3
12.0 (Note)
+3.3 VDC
0.5
16.7 (Note)
-12 VDC
0.0
0.3
+5 VSB
0.0
2.0
2.5
Note: Total combined output of 3.3 V and 5 V is <= 63 W
Peak currents may last up to 17 seconds with not more than one occurrence per minute
Figure 2. Cross loading Graph for 180W configuration
180W Cross Regulation
(5V rail + 3.3V rail vs. 12V)
5V + 3.3V power (watts)
70
60
50
40
Combined Power
(5V rail + 3.3V rail)
30
20
10
0
0
50
100
150
200
12V power (watts)
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TFX12V Power Supply Design Guide
Version 1.2
Table 4.
Typical Power Distribution for 220 W TFX12V Configurations
Minimum
Current (amps)
Output
Rated Current
(amps)
+12 VDC
1.0
15.0
+5 VDC
0.3
13.0 (Note)
+3.3 VDC
0.5
17.0 (Note)
-12 VDC
0.0
0.3
+5 VSB
0.0
2.0
Peak Current
(amps)
17.0
2.5
Note: Total combined output of 3.3 V and 5 V is <= 80 W
Peak currents may last up to 17 seconds with not more than one occurrence per minute
Figure 3. Cross loading Graph for 220W configuration
220W Cross Regulation
(5V rail + 3.3V rail vs. 12V)
5V + 3.3V power (watts)
90
80
70
60
50
40
Combined Power
(5V rail + 3.3V rail)
30
20
10
0
0
50
100
150
12V power (watts)
12
200
TFX12V Power Supply Design Guide
Version 1.2
Table 5. Typical Power Distribution for 240 W TFX12V Configurations
Minimum
Current (amps)
Output
Rated Current
(amps)
+12 VDC
1.0
16.0
+5 VDC
0.3
19.0 (Note)
+3.3 VDC
0.5
18.0 (Note)
-12 VDC
0.0
0.3
+5 VSB
0.0
2.0
Peak Current
(amps)
18.0
2.5
Note: Total combined output of 3.3 V and 5 V is <=105 W
Peak currents may last up to 17 seconds with not more than one occurrence per minute
Figure 4. Cross loading Graph for 240W configuration
240W Cross Regulation
(5V rail + 3.3V rail vs. 12V)
5V + 3.3V power (watts)
120
100
80
Combined Power
(5V rail + 3.3V rail)
60
40
20
0
0
50
100
150
200
250
12V power (watts)
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TFX12V Power Supply Design Guide
Version 1.2
2.2.4 Power Limit / Hazardous Energy Levels
Under normal or overload conditions, no output shall continuously provide 240 VA under any conditions of
load including output short circuit, per the requirement of UL 1950/CSA 950 / EN 60950/IEC 950
specification.
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TFX12V Power Supply Design Guide
Version 1.2
2.2.5 Efficiency General
The power supply should be a minimum of 70% efficient under “Full” load, 6 0% under “typical” load, and
50% in a “light” load idle condition. The efficiency of the power supply should be tested at nominal input
voltage of 115VAC input and 230VAC input, under the load conditions defined in Table 6, and under the
temperature and operating conditions defined in Section 3. The loading condition for testing efficiency
shown in Table 6 represents a Fully loaded system, a 50% loaded system, and a 20% loaded system.
Table 6.
Efficiency Vs Load
Loading
Full load
Minimum Efficiency
Table 7.
Typical load
70%
Light load
60%
50%
Loading table for Efficiency measurements
180W (loading shown in Amps)
Loading
+12V
+5V
+3.3V
-12V
+5Vsb
Full
11
4
5.8
0.3
1.0
Typical
7
3
4
0.1
1.0
Light
2
0.3
0.5
0.0
1.0
220W (loading shown in Amps)
Loading
+12V
+5V
+3.3V
-12V
+5Vsb
Full
13
5
9
0.3
1.0
Typical
8
3
5
0.1
1.0
Light
3
0.5
2.0
0.0
1.0
240W (loading shown in Amps)
Loading
+12V
+5V
+3.3V
-12V
+5Vsb
Full
14
6
10
0.3
1.0
Typical
9
3
6
0.1
1.0
Light
4
1.0
3.0
0.0
1.0
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TFX12V Power Supply Design Guide
Version 1.2
2.2.5.1
Energy Star*
The “Energy Star” efficiency requirements of the power supply depend on the intended system configuration.
In the low power / sleep state (S1 or S3) the system should consume power in accordance with the values
listed in Table 8.
Table 8.
Energy Star Input Power Consumption
Maximum Continuous Power Rating of Power
Supply
RMS Watts from the AC Line in Sleep/low-Power
Mode
< 200 W
< 15 W
> 200 W < 300 W
< 20 W
> 300 W < 350 W
< 25 W
> 350 W < 400 W
< 30 W
> 400 W
10% of the maximum continuous output rating
Note: To help meet the “Energy Star” system requirements, it is recommended that the power supply have > 50%
efficiency in standby mode.
2.2.5.2
Other Low Power System Requirements
To help meet the Blue Angel* system requirements, RAL-UZ 78, US Presidential executive order 13221, future
EPA requirements, and other low Power system requirements the +5 VSB standby supply efficiency should be
as high as possible. Standby efficiency is measured with the main outputs off (PS_ON# high state). Standby
efficiency should be greater than 50% with a load of 100mA.
2.2.6 Output Ripple/Noise
The output ripple/noise requirements listed in Table 9 should be met throughout the load ranges specified
in Section 2.2.3 and under all input voltage conditions as specified in Section 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 10µF electrolytic capacitor to simulate system
loading. See Figure 5.
Table 9.
DC Output Noise/Ripple
Output
Maximum Ripple and Noise
(mVpp)
+12 VDC
120
+5 VDC
50
+3.3 VDC
50
-12 VDC
120
+5 VSB
50
* Other names and brands may be claimed as the property of others.
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TFX12V Power Supply Design Guide
Version 1.2
Power Supply
AC Hot
AC Neutral
V out
10uf
V return
0.1uf
Load
Load must be
isolated from the
ground of the
power supply.
AC Ground
General Notes:
1. Load the output with its minimum load
current.
2. Connect the probes as shown.
3. Repeat the measurement with maximum
load on the output.
Scope
Filter Note:
0.1uf - Kemet, C1206C104K5RAC or equivalent
10uf - United Chemi-con, 293D106X0025D2T or
equivalent
Scope Note:
Use Tektronix † TDS460 Oscilloscope or
equivalent and a P6046 probe or equivalent.
Figure 5. Differential Noise Test Setup
* Other names and brands may be claimed as the property of others.
2.2.7 Output Transient Response
Table 10 summarizes the expected output transient step sizes for each output. The transient load slew rate
is = 1.0 A/µs.
Table 10.
DC Output Transient Step Sizes
Output
Maximum Step Size
(% of rated output amps)
+12 VDC
50%
+5 VDC
30%
+3.3 VDC
30%
Maximum Step Size
(amps)
-12 VDC
0.1 A
+5 VSB
0.5 A
Note: For example, for a rated +5 VDC output of 14 A, the transient step would be 30% × 14 A = 4.2 A
Output voltages should remain within the regulation limits of Table 2, Section 2.2.1, for instantaneous
changes in load as specified in Table 10 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 3.1 and Capacitive loading per Table 11
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TFX12V Power Supply Design Guide
Version 1.2
2.2.8 Capacitive Load
The power supply should be able to power up and operate with the regulation limits defined in Table 2,
Section 2.2.1, with the following capacitances simultaneously present on the DC outputs.
Table 11.
Output Capacitive Loads
Output
Capacitive Load
(µF)
+12 VDC
5,000
+5 VDC
10,000
+3.3 VDC
6,000
-12 VDC
350
+5 VSB
350
2.2.9 Closed-loop Stability
The power supply shall be unconditionally stable under all line/load/transient load conditions including
capacitive loads specified in Section 2.2.8. A minimum of 45 degrees phase margin and 10 dB gain margin
is recommended at both the maximum and minimum loads.
2.2.10
+5 VDC / +3.3 VDC Power Sequencing
The +12 VDC 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 the +12 VDC or +5 VDC output reaching its
minimum in-regulation level and +3.3 VDC reaching its minimum in-regulation level must be ≤ 20 ms.
2.2.11
Voltage Hold-up Time
The power supply should maintain output regulations per Section 2.2.1 despite a loss of input power at the
low-end nominal range—115 VAC / 57 Hz or 230 VAC / 47 Hz - at maximum continuous output load as
applicable for a minimum of 17 ms.
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TFX12V Power Supply Design Guide
Version 1.2
2.3 Timing / Housekeeping / Control
Figure 6. Power Supply Timing
Notes: T1 is defined in Section 2.3.4. , T2 in Section 2.3.5. ,T3, T4, T5, and T6 are defined in Table 12.
2.3.1 PWR_OK
PWR_OK is a “power good” signal. This signal should be asserted high by the power supply to indicate that
the +12 VDC, +5 VDC, and +3.3 VDC outputs are above the under voltage thresholds listed in Table 2 in
Section 2.2.1 and that sufficient mains energy is stored by the converter to guarantee continuous power
operation within specification for at least the duration specified in Section 2.2.11, “Voltage Hold-up Time.”
Conversely, PWR_OK should be de-asserted to a low state when any of the +12 VDC, +5 VDC, or +3.3 VDC
output voltages falls below its under voltage threshold, or when mains power has been removed for a time
sufficiently long such that power supply operation cannot be guaranteed beyond the power-down warning
time. The electrical and timing characteristics of the PWR_OK signal are given in Table 12 and in Figure 6.
Table 12.
PWR_OK Signal Characteristics
Signal Type
+5 V TTL compatible
Logic level low
< 0.4 V while sinking 4 mA
Logic level high
Between 2.4 V and 5 V output while sourcing 200 µA
High-state output impedance
1 kΩ from output to common
PWR_OK delay
100 ms < T 3 < 500 ms
PWR_OK rise time
T4 ≤ 10 ms
AC loss to PWR_OK hold-up time
T5 ≥ 16 ms
Power-down warning
T6 ≥ 1 ms
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2.3.2 PS_ON#
PS_ON# is an active-low, TTL-compatible signal that allows a motherboard to remotely control the power
supply in conjunction with features such as soft on/off, Wake on LAN *, or wake-on-modem. When PS_ON#
is pulled to TTL low, the power supply should turn on the four main DC output rails: +12 VDC, +5 VDC, +3.3
VDC, and -12 VDC. When PS_ON# is pulled to TTL high or open-circuited, the DC output rails should not
deliver current and should be held at zero potential with respect to ground. PS_ON# has no effect on the +5
VSB output, which is always enabled whenever the AC power is present. Table 13 lists PS_ON# signal
characteristics.
The power supply shall provide an internal pull-up to TTL high. The power supply shall also provide debounce circuitry on PS_ON# to prevent it from oscillating on/off at startup when activated by a mechanical
switch. The DC output enable circuitry must be SELV-compliant.
The power supply shall not latch into a shutdown state when PS_ON# is d riven active by pulses between
10ms to 100ms during the decay of the power rails.
Table 13.
PS_ON# Signal Characteristics
Parameter
Minimum
VIL, Input Low Voltage
0.0 V
Maximum
0.8 V
IIL, Input Low Current (Vin = 0.4 V)
-1.6 mA
VIH, Input High Voltage (Iin = -200 µA)
2.0 V
VIH open circuit, Iin = 0
5.25 V
Hysteresis ≥ 0.3 V
Disable
≥ 2.0 V
PS is
disabled
≤ 0.8 V
PS is
enabled
Enable
0.8
2.0
5.25 = Maximum OpenCircuit Voltage
PS_ON# Voltage
Figure 7. PS_ON# Signal Characteristics
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2.3.3 +5 VSB
+5 VSB is a standby supply output that is active whenever the AC power is present. This output provides a
power source for circuits that must remain operational when the five main DC output rails are in a disabled
state. Example uses include soft power control, Wake on LAN, wake-on-modem, intrusion detection, or
suspend state activities.
The +5 VSB output should be capable of delivering a minimum of 2.0 A. at +5 V ± 5% to external circuits.
The power supply must be able to provide the required power during a "wake up" event. If an external USB
device generates the event, there may be peak currents as high as 2.5 A., lasting no more than 500 ms.
Over current protection is required on the +5 VSB output regardless of the output current rating. This
ensures the power supply will not be damaged if exte rnal circuits draw more current than the supply can
provide.
2.3.4 Power-on Time
The power-on time is defined as the time from when PS_ON# is pulled low to when the +12 VDC, +5 VDC,
and +3.3 VDC outputs are within the regulation ranges s pecified in Section 2.2.1. The power-on time shall
be less than 500 ms (T 1 < 500 ms).
+5 VSB shall have a power-on time of two seconds maximum after application of valid AC voltages.
2.3.5 Rise Time
The output voltages shall rise from ≤10% of nominal to within the regulation ranges specified in Section
2.2.1 within 0.2 ms to 20 ms (0.2 ms ≤ T2 ≤ 20 ms).
There must be a smooth and continuous ramp of each DC output voltage from 10% to 90% of its final set
point within the regulation band, while loaded as specified in Section 2.2.1.
The smooth turn-on requires that, during the 10% to 90% portion of the rise time, the slope of the turn-on
waveform must be positive and have a value of between 0 V/ms and [Vout, nominal / 0.1] V/ms. Also, for any 5
ms segment of the 10% to 90% rise time waveform, a straight line drawn between the end points of the
waveform segment must have a slope ≥ [Vout, nominal / 20] V/ms.
2.3.6 Overshoot at Turn-on / Turn-off
The output voltage overshoot upon the application or removal of the input voltage, or the assertion/deassertion of PS_ON#, under the conditions specified in Section 3.1, shall be less than 10% above the
nominal voltage. No voltage of opposite polarity shall be present on any output during turn-on or turn-off.
2.3.7 Reset after Shutdown
If the power supply latches into a shutdown state because of a fault condition on its outputs, the power
supply shall return to normal operation only after the fault has been removed and the PS_ON# has been
cycled OFF/ON with a minimum OFF time of one second.
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2.3.8 +5 VSB at AC Power-down
After AC power is removed, the +5 VSB standby voltage output should remain at its steady state value for the
minimum hold-up time specified in Section 2.2.11 until the output begins to decrease in voltage. The
decrease shall be monotonic in nature, dropping to 0.0 V. There shall be no other disturbances of this
voltage at or following removal of AC power.
2.4 Output Protection
2.4.1 Over Voltage Protection
The over voltage sense circuitry and reference shall reside in packages that are separate and distinct from
the regulator control circuitry and reference. No single point fault shall be able to cause a sustained over
voltage condition on any or all outputs. The supply shall provide latch-mode over voltage protection as
defined in Table 14.
Table 14.
Over Voltage Protection
Output
Minimum
Nominal
Maximum
Unit
+12 VDC
13.4
15.0
15.6
Volts
+5 VDC
5.74
6.3
7.0
Volts
+3.3 VDC
3.76
4.2
4.3
Volts
2.4.2 Short-circuit Protection
An output short circuit is defined as any output impedance of less than 0.1 ohms. The power supply shall
shut down and latch off for shorting the +3.3 VDC, +5 VDC, or +12 VDC rails to return or any other rail.
Shorts between main output rails and +5 VSB shall not cause any damage to the power supply. The power
supply shall either shut down and latch off or fold back for shorting the negative rails. +5 VSB must be
capable of being shorted indefinitely, but when the short is removed, the power supply shall recover
automatically or by cycling PS_ON#. The power supply shall be capable of withstanding a continuous short
circuit to the output without damage or overstress to the unit (for example, to components, PCB traces, and
connectors) under the input conditions specified in Section 3.1.
2.4.3 No-load Operation
No damage or hazardous condition should occur with all the DC output connectors disconnected from the
load. The power supply may latch into the shutdown state.
2.4.4 Over Current Protection
Overload currents applied to each tested output rail cause the output to trip before reaching or exceeding
240 VA. For testing purposes, the overloaded currents should be ramped at a minimum rate of 10 A/s
starting from full load.
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2.4.5 Over-temperature Protection
As an option, the power supply may include an over-temperature protection sensor, which can trip and shut
down the power supply at a preset temperature point. Such an overheated condition is typically the result of
internal current overloading or a cooling fan failure. If the protection circuit is non-latching, then it should
have hysteresis built in to avoid intermittent tripping.
2.4.6 Output Bypass
The output return may be connected to the power supply chassis, and will be connected to the system
chassis by the system components.
3 Mechanical
3.1 Labeling /Marking
The following is a non-inclusive list of suggested markings for each power supply unit. Product regulation
stipulations for sale into various geographies may impose additional labeling requirements.
•
•
•
•
Manufacturer information: manufacturer's name, part number and lot date code, etc., in humanreadable text and/or bar code formats
Nominal AC input operating voltages (100-127 VAC and 200-240 VAC) and current rating certified by all
applicable safety agencies
DC output voltages and current ratings
Access warning text (“Do not remove this cover. Trained service personnel only. No user serviceable
components inside.”) must be in English, German, Spanish, French, Chinese, and Japanese with
universal warning markings
3.2 Physical Dimensions
The power supply shall be enclosed and meet the physical outline shown in Figure 8, as applicable.
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Figure 8. Power Supply Dimensions and Recommended Feature Placements (not to scale)
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Figure 9. Power Supply Mounting Slot Detail
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3.3 Mounting Options
The TFX12V mechanical design provides two options for mounting in a system chassis. The unit can be
mounted using one of the mounting holes on the front end (non-vented end) or a chassis feature can be
designed to engage the slot provided in the bottom of the supply. In order to accommodate different system
chassis layouts, the TFX12V power supply is also designed to mount in two o rientations (fan left and fan
right) as shown in Figure 10. A mounting hole and slot should be provided for each orientation as shown in
Figure 8. Details of a suggested geometry for the mounting slot are shown in Figure 9.
Figure 10. Fan Right and Fan Left Orientations of Power Supply in a Chassis
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TFX12V Power Supply Design Guide
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3.4 Chassis Requirements
To ensure the power supply can be easily integrated, the following features should be designed into a
chassis intended to use a TFX12V power supply:
•
Chassis cutout (normally in the rear panel of the chassis) as shown in Figure 11.
•
EITHER a mounting bracket to interface with the forward mounting hole on the power supply OR a
mounting tab as shown in Figure 12 to interface with the mounting slot on the bottom of the power
supply
Figure 11. Suggested TFX12V Chassis Cutout
Figure 12. Suggested Mounting Tab (chassis feature)
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TFX12V Power Supply Design Guide
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3.5 Airflow / Fan
The designer’s choice of a power supply cooling solution depends in part on the targeted end-use system
application(s). At a minimum, the power supply design must ensure its own reliable and safe operation.
Fan location/direction: In general, exhausting air from the system chassis enclosure via a power supply fan
is the preferred, most common, and most widely applicable sys tem-level airflow solution. The location of
the fan can have a large effect on how efficiently this air is exhausted. The location of the fan shown in
Figure 8 allows the fan to be located close to the processor cooling solution w hen used in the common fan
left configuration shown in Figure 10. This close proximity of the fan will aid in the evacuation of heated air
and helps keep the total system cooler.
Fan size/speed: The TFX12V power supply has an 80 mm axial fan as shown in Figure 8. It is
recommended that a thermally sensitive fan speed control circuit be used to balance system -level thermal
and acoustic performance. The circuit typically senses the temperature of the secondary heat sink and/or
incoming ambient air and adjusts the fan speed as necessary to keep power supply and system
component temperatures within specifications. Both the power supply and system designers should be
aware of the dependencies of the power supply and system temperatures on the control circuit response
curve and fan size and should specify them carefully.
The power supply fan should be turned off when PS_ON# is de-asserted (high). In this state, any remaining
active power supply circuitry must rely only on passive convection for cooling.
Venting: In general, more venting in a power supply case yields reduced airflow impedance and improved
cooling performance. Intake and exhaust vents should be as large, open, and unobstructed as possible so
as not to impede airflow or generate excessive acoustic noise. In particular, avoid placing objects within 0.5
inches of the intake or exhaust of the fan itself. A raised wire fan grill is recommended instead of a stamped
metal vent for improved airflow and reduced acoustic noise for the intake vent. Figure 8 shows the
suggested TFX12V exhaust vent pattern.
Considerations to the previous venting guidelines are:
•
•
Openings must be sufficiently designed to meet the safety requirements d escribed in Section 5.
Larger openings yield decreased EMI-shielding performance. The suggested pattern in Figure 8
sufficiently shields EMI in most power supplies, but the design should always be tested as outlined in
Section 6.1.
NOTE:
Venting in inappropriate locations can detrimentally allow airflow to bypass those areas where it is needed.
3.6 AC Connector
The AC input receptacle should be an IEC 320 type or equivalent. In lieu of a dedicated switch, the IEC 320
receptacle may be considered the mains disconnect.
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3.7 DC Connectors
Figure 13 shows pin outs and profiles for typical TFX12V power supply DC harness connectors. The
TFX12V requires an additional two-pin, power connector.
UL Listed or recognized component appliance wiring material rated min 85 °C, 300 VDC shall be used for
all output wiring.
There are no specific requirements for output wire harness lengths, as these are largely a function of the
intended end-use chassis, motherboard, and peripherals. Ideally, wires should be short to minimize
electrical/airflow impedance and simplify manufacturing, yet they should be long enough to make all
necessary connections without any wire tension (which can cause disconnections during shipping and
handling). Recommended minimum harness lengths for general-use power supplies is 150 mm for all
wire harnesses. Measurements are made from the exit port of the power supply case to the wire side of the
first connector on the harness.
Figure 13. TFX12V Connectors (Pin-side view, not to scale)
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3.7.1 TFX12V Main Power Connector
Connector: MOLEX * 39-01-2200 or equivalent
(Mating motherboard connector is Molex 39-29-9202 or equivalent)
18 AWG is suggested for all wires except for the +3.3 V supply and sense return wires combined into pin 11
(22 AWG).
Pin
Signal
Color
Pin
Signal
Color
1
+3.3 VDC
Orange
11
+3.3 VDC
Orange
[11]
[+3.3 V default
sense]
[Brown]
2
+3.3 VDC
Orange
12
-12 VDC
Blue
3
COM
Black
13
COM
Black
4
+5 VDC
Red
14
PS_ON#
Green
5
COM
Black
15
COM
Black
6
+5 VDC
Red
16
COM
Black
7
COM
Black
17
COM
Black
8
PWR_OK
Gray
18
Reserved
NC
9
+5 VSB
Purple
19
+5 VDC
Red
10
+12 VDC
Yellow
20
+5 VDC
Red
3.7.2 Peripheral Connector(s)
Connector: AMP* 1-480424-0 or MOLEX * 8981-04P or equivalent.
Contacts: AMP 61314-1 or equivalent.
Pin
Signal
18 AWG Wire
1
+12 VDC
Yellow
2
COM
Black
3
COM
Black
4
+5 VDC
Red
3.7.3 Floppy Drive Connector
Connector: AMP* 171822-4 or equivalent
Pin
Signal
20 AWG Wire
1
+5 VDC
Red
2
COM
Black
3
COM
Black
4
+12 VDC
Yellow
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3.7.4 +12 V Power Connector
Connector: MOLEX * 39-01-2040 or equivalent (Mating motherboard connector is Molex*
39-29-9042 or equivalent)
Pin
Signal
18 AWG Wire
Pin
Signal
18 AWG Wire
1
COM
Black
3
+12 VDC
Yellow
2
COM
Black
4
+12 VDC
Yellow
3.7.5 Serial ATA Power Connector
This is an optional connector for systems with Serial ATA devices.
The detailed requirements for the Serial ATA Power Connector can be found in the “Serial ATA: High Speed
Serialized AT Attachment” specification, Section 6.3 “Cables and connector specification”
Connector: MOLEX * 88751 or equivalent.
Wire
Signal
18 AWG Wire
5
+3.3 VDC
Orange
4
COM
Black
3
+5 VDC
Red
2
COM
Black
1
+12 VDC
Yellow
Wire#
5
4
3
2
1
Figure 14. Serial ATA connector
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4 Environmental
The following subsections define recommended environmental specifications and test parameters, based
on the typical conditions a TFX12V power supply unit may be subjected to during operation or shipment.
4.1 Temperature
Operating ambient: +10 °C to +50 °C (At full load, with a maximum temperature rate of change of 5 °C/10
minutes, but no more than 10 °C/hr.)
Non-operating ambient: -40 °C to +70 °C (Maximum temperature rate of change of 20 °C/hr.)
4.2 Thermal Shock (Shipping)
Non-operating: -40 °C to +70 °C
15 °C/min ≤ dT/dt ≤ 30 °C/min. Tested for 50 cycles; Duration of exposure to temperature extremes for each
half cycle shall be 30 minutes.
4.3 Relative Humidity
Operating: To 85% relative humidity (non-condensing)
Non-operating: To 95% relative humidity (non-condensing)
Note: 95% RH is achieved with a dry bulb temperature of 55 °C and a wet bulb temperature of 54 °C.
4.4 Altitude Requirement
Operating: To 10,000 ft
Non-operating: To 50,000 ft
4.5 Mechanical Shock
Non-operating: 50 g, trapezoidal input; velocity change ≥ 170 in/s
Three drops on each of six faces are applied to each sample.
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4.6 Random Vibration
Non-operating: 0.01 g²/Hz at 5 Hz, sloping to 0.02 g²/Hz at 20 Hz, and maintaining 0.02 g²/Hz from 20 Hz to
500 Hz. The area under the PSD curve is 3.13 gRMS. The duration shall be 10 minutes per axis for all three
axes on all samples.
4.7 Acoustics
Sound Power: The power supply assembly shall not produce a declared sound power level greater than
3.8 BA. Sound power determination is to be performed at 43C, 50% of rated load, at sea level. This test
point is chosen to represent the environment seen inside a typical system at the idle acoustic test condition,
with the 43C being derived from the standard ambient assumption of 23C, with 20C added for the
temperature rise within the system (what is typically seen by the inlet fan). The declared sound power level
shall be measured according to ISO 7779 and reported according to ISO 9296.
Pure Tones: The power supply assembly shall not produce any prominent discrete tone determined
according to ISO 7779, Annex D.
4.8 Ecological Requirements
The following materials must not be used during design and/or manufacturing of this product:
•
•
•
•
Cadmium shall not be used in painting or plating.
Quaternary salt and PCB electrolytic capacitors shall not be used.
CFC’s or HFC’s shall not be used in the design or manufacturing process.
Mercury shall not be used.
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5 Safety
The following subsections outline s ample product regulations requirements for a typical power supply.
Actual requirements will depend on the design, product end use, target geography, and other variables.
Consult your company’s Product Safety and Regulations department for more details.
5.1 North America
The power supply must be certified by an NRTL (Nationally Recognized Testing Laboratory) for use in the
USA and Canada under the following conditions:
•
•
•
The supply must be recognized for use in Information Technology Equipment including Electrical
Business Equipment per UL 60950, 3rd edition, 2000. The certification must include external
enclosure testing for the AC receptacle side of the power supply.
The supply must have a full complement of tests conducted as part of the certification, such as input
current, leakage current, hi-pot, temperature, energy discharge test, transformer output characterization
test (open-circuit voltage, short-circuit current, and maximum VA output), and abnormal testing (to
include stalled-fan tests and voltage-select–switch mismatch).
The enclosure must meet fire enclosure mechanical test requirements per clauses 2.9.1 and 4.2 of the
above-mentioned standard.
100% production HiPot testing must be included and marked as such on the power supply enclosure.
There must not be unusual or difficult conditions of acceptability such as mandatory additional cooling or
power de-rating. The insulation system shall not have temperatures exceeding their rating when tested in
the end product.
The certification mark shall be marked on each power supply.
The power supply must be evaluated for operator-accessible secondary outputs (reinforced insulation) that
meet the requirements for SELV and do not exceed 240 VA under any condition of loading.
The proper polarity between the AC input receptacle and any printed wiring boards connections must be
maintained (that is, brown=line, blue=neutral, and green or green/yellow =earth/chassis).
Failure of any single component in the fan-speed control circuit shall not cause the internal component
temperatures to exceed the abnormal fault condition temperatures per the IEC 60950 3rd ed., 1999
Specification.
5.2 International
The vendor must provide a complete CB certificate and test report to IEC 60950: 3rd ed., 1999 . The CB
report must include ALL CB member country national deviations. CB report must include evaluation to EN
60950: 2000. All evaluations and certifications must be for reinforced insulation between primary and
secondary circuits.
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TFX12V Power Supply Design Guide
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6 Electromagnetic Compatibility
The following subsections outline applicable product regulatory requirements for the TFX12V power supply.
Additional requirements may be applied dependent upon the design, product end use (e.g., medical
equipment and hazardous locations), target geography, and other variables.
6.1 Emissions
The power supply shall comply with FCC Part 15, EN55022: 1998 and CISPR 22: 1997, meeting Class B
for both conducted and radiated emissions with a 4 dB margin. Tests shall be conducted using a shielded
DC output cable to a shielded load. The load shall be adjusted as follows for three tests: No load on each
output; 50% load on each output; 100% load on each output. Tests will be performed at 100 VAC 50Hz, 120
VAC 60 Hz, and 230 VAC 50 Hz power.
6.2 Immunity
The power supply shall comply with EN 55024:1998 and CISPR 24 specifications prior to sale in the EU
(European Union), Korea, and possibly other geographies.
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TFX12V Power Supply Design Guide
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6.3 Input Line Current Harmonic Content
For sales in the EU (European Union) the power supply shall meet the requirements of
EN61000-3-2 Class D and the Guidelines for the Suppression of Harmonics in Appliances and General Use
Equipment Class D for harmonic line current content at full rated power. See Table 15 for the harmonic
limits.
Table 15.
Harmonic Limits, Class D Equipment
Harmonic Order n
Per: EN 61000-3-2
Per: JEIDA MITI
Maximum permissible Harmonic
current at 230 VAC / 50 Hz in Amps
Maximum permissible Harmonic
current at 100VAC / 50 Hz in Amps
Odd harmonics
3
2.3
5.29
5
1.14
2.622
7
0.77
1.771
9
0.4
0.92
11
0.33
0.759
13
0.21
0.483
15≤ n ≤39
0.15 x (15/n)
0.345 x (15/n)
6.4 Magnetic Leakage Fields
A PFC choke magnetic leakage field should not cause any interference with a high-resolution computer
monitor placed next to or on top of the end-use chassis.
6.5 Voltage Fluctuations and Flicker
The power supply shall meet the specified limits of the EN61000-3-3 Specification for voltage fluctuations
and flicker for equipment drawing not more then16 AAC, connected to low voltage distribution systems.
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TFX12V Power Supply Design Guide
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7 System Cooling Considerations
The power supply fan location allows the system designer to utilize the airflow to help cool critical
components such as the processor and chipset. Please note that the fan pulls air from the system, instead
of blowing hot air in, so components must be placed such that airflow is directed across critical
components. Cables, etc must not impede airflow.
For more information on system thermal design, please refer to http://www.formfactors.org/.
8 Reliability
The de-rating process promotes quality and high reliability. All electronic components should be designed
with conservative device d-ratings for use in commercial and industrial environments.
9 Applicable Documents
The following documents support this design guide as additional reference material.
Document Title
Description
FCC Rules Part 15, Class B
Title 47, Code of Federal Regulations, Part 15
ICES-003: 1997, Class B
Interference-Causing Equipment Standard – Digital Apparatus
EN 55022: 1998 +
Amendment A1:2000 Class B
Information Technology Equipment – Radio disturbance characteristics –
Limits and methods of measurement
CISPR 22: 1997, Class B
Information Technology Equipment – Radio disturbance characteristics –
Limits and methods of measurement
AS/NZS 3548:1995, Class B
Information Technology Equipment – Radio disturbance characteristics –
Limits and methods o f measurement
EN 55024:1998
Information Technology Equipment – Immunity Characteristics – Limits and
methods of measurement
IEC 60950, 3 rd ed., 1999
Safety of Information Technology Equipment
EN 60950: 2000
Safety of Information Technology Equipment
rd
UL 60950, 3 ed., 2000
Safety of Information Technology Equipment
CSA 22.2 No. 60950-00
Safety of Information Technology Equipment
37