NEW
Product
1. Introduction 2
2. Models 2
3. General Description
Electrical Diagram 2
Physical Construction 2
4. Features and Functions
Wide Operating Temperature Range 3
Over-Temperature Protection 3
Over-Voltage Protection 3
Safe Operating Area 3
Current Limit and Short Circuit Protection 3
Remote ON/OFF 4
Output Voltage Adjustment 4
5. Safety
Isolation 7
Input Fusing 7
6. EMC
Conducted Emissions 8
Radiated Emissions 8
Common Mode Noise 8
7. Use in a Manufacturing Environment
Resistance to Soldering Heat 8
Water Washing 9
ESD Control 9
8. Applications
Optimum PCB Layout 9
Optimum Thermal Performance 9
Design Examples 9
Active Inrush Current Limiting 11
Parallel and Series Operation 11
Output Noise and Ripple Measurement 11
Appendix 1 12
EXB50 Dual
Application Note
127 Rev. 02 /October 2001
1. Introduction
The EXB50 Dual series is a family of open-frame DC/DC converters
providing two positive outputs. High-efficiency operation is achieved
through the use of synchronous rectification and planar magnetics.
Both outputs are independently regulated, and provide an ultra-wide
trim range. The EXB50 Dual series offers a wide output current SOA
(Safe Operating Area) and load mix flexibility. Through a control input
the unit can be remotely controlled, and sent into a low-dissipation
sleep mode. An independent latching over-voltage protection (OVP)
feature for both outputs is provided. The OVP trip-point is also
trimmable, i.e. tracks the output voltage setpoint. Over-temperature
protection (OTP) protects the unit from thermal stress. Automated
manufacturing methods together with an extensive qualification
program have produced a highly reliable range of converters.
2. Models
Due to its ultra-wide trim range, any two output voltages between
1.5V and 5.25V can be covered with one model. This allows the
EXB50 Dual to deliver any arbitrary dual positive output voltage
combination.
Table 1 - Output Voltages
Features
• Industry standard half-brick pin-out and footprint: 61.0 x 57.9
x 10.0 mm (2.4 x 2.3 x 0.4 inches)
• Wide operating ambient temperature range (typically –40°C to
+70°C natural convection)
• Two independently regulated positive outputs
• Ultra-wide output voltage adjustability
• Load mix flexibility
• No minimum load on either output
• Primary side control input for remote on/off control
• Constant switching frequency
• Continuous short circuit protection
• Latching output overvoltage protection
• Input undervoltage protection
3. General Description
3.1 Electrical Diagram
A block diagram of the EXB50 Dual converter is shown in Figure 1.
High efficiency power conversion is achieved through the use of
synchronous rectification for both outputs, as well as planar
magnetic components.
The power stage topology is buck-derived. Power is magnetically
transferred across the isolation barrier through an isolating
transformer. The secondary side voltage is rectified by synchronous
rectifiers providing an internal DC voltage bus. Two equivalent
synchronous buck converters derive the two independently regulated
output voltages Vo1 and Vo2 from the internal DC voltage bus.
Two tightly regulated positive outputs are provided. The grounds of
the outputs are connected internally (i.e. Vo1- is connected to Vo2-).
Both outputs are independently trimmable over an ultra-wide range
of 1.5V to 5.25V each.
Both outputs can be shut down via a primary side control input. The
control input is compatible with popular logic devices. By default the
control input is "active high", i.e. the converter is enabled if the
control input is high (or floating) and disabled if the control input is
low.
Both outputs are independently monitored for over-voltages. If an
over-voltage due to an inter nal fault is detected on any of the two
outputs, the converter will latch off, disabling both outputs.
The converter is also equipped with over-temperature sensors. If the
converter is over-loaded, or the ambient temperature gets too high,
the converter will shut down until the temperature falls below a
certain threshold. After cooling down the converter will operate
again.
An internal second order input filter (LC) smoothes the input current
and reduces conducted and radiated EMI. Further improvement can
be achieved through the use of an optional external input filter.
Figure 1 - Electrical Block Diagram
3.2 Physical Construction
The EXB50 Dual series is constructed using a single multi-layer FR4
PCB. SMT components are placed on both sides of the PCB and in
general, the heavier power components are mounted on the top side
in order to optimise heat dissipation.
• Two independently regulated positive outputs
• Each output offers ultra-wide output voltage
trim range (1.5V....5.25V)
• High efficiency topology, 89% typical
• Approved to IEC60950, UL/cUL60950
• Operating ambient temperature of -40°C to
+70°C (natural convection)
• No minimum load on either output
• Complies with ETS 300 019-1-3/2-3
• Complies with ETS 300 386-1
2
EXB50 Dual SERIES |Application Note 127 Rev. 02
Vin Input Filter
Primary
Control
Sync. Buck
Converter
Synchronous
Rectifiers
PWM
Control1
PWM
Control2
Sync. Buck
Converter
Secondary
Control
Control On/Off
Control
Isolation Barrier
(Basic Insulation)
Feedback
Adjustability
Feedback
Adjustability
Synchronisation
OTP OVP
OVP
Vo1
Trim1
Vo2
Trim2
Model Input Voltage Output Voltage
#1 #2
EXB50-48D05-3V3 36V-75V 1.5V-5.25V 1.5V-5.25V
Default Default
(untrimmed): (untrimmed):
5.0V 3.3V
also be entered due to a loss of control of the environmental
conditions (e.g. increase in converter temperature due to a failing
fan).
4.3 Over-voltage Protection
Both outputs are monitored for over-voltages to protect the load
circuitry from damage should the converter fail.
OVP trip points are set at 125% of the output voltage set-point for
each output. Note that the OVP threshold tracks the output voltage
set-point when trimmed over the full 1.5V to 5.25V range.
Response time to an OVP event is typically around 2ms. If an OVP
event is detected the converter will latch off disabling both outputs.
The converter will remain shut down until the input voltage is cycled.
Alternatively, the converter can be re-enabled by toggling the control
input.
Note that the converter does not provide clamp devices (e.g. TVS)
across the outputs. This means that the converter will detect over-
voltages present at the outputs, but it cannot clamp them. Users
may want to clamp over-voltages by exter nal means (e.g. TVS,
crowbars).
4.4 Safe Operating Area
The Safe Operating Area (SOA) of the EXB50 Dual converter is
shown in Figure 2. It can be seen that each output Io1and Io2can
deliver an output current in the range of 0A to 7.5A. Zero load
operation and load mix flexibility are valuable features of the EXB50
Dual converter. Assuming the converter is operated within its thermal
hotspot constraints, it can deliver a total output current Io(total)
(=Io1+Io2) of 15A. The SOA remains valid across the full trim range of
the converter.
Figure 2 - Maximum Output Current Safe Operating Area
It should be noted that the SOA shown in Figure 2 is valid only if the
converter is operated within its thermal specification. See section
Optimum Thermal Performance for further discussions.
4.5 Current Limit and Short Circuit Protection
The EXB50 Dual converter has a built in current limit function and
continuous short circuit protection. Both the specified maximum
output current and the current limit inception point refer to the sum
of the output currents Io(total) (i.e. Io1+Io2).
If the output currents Io1and Io2are outside the SOA the converter is
being operated in overload mode. None of the datasheet
specifications are guaranteed when in overload mode. While
The converter is sold as an open-frame product and no case is
required. The open frame design has several advantages over
encapsulated closed devices. Among these advantages are:
•Cost: No potting compound, case or associated process costs
involved.
•Thermals: The heat is removed from the heat generating
components without heating more sensitive, less tolerant
components such as opto-couplers.
•Environmental: Some encapsulants are not kind to the
environment and create problems in incinerators. In addition open
frame converters are more easily re-cycled.
•Reliability: Open Frame modules are more reliable for a number
of reasons.
A separate paper discussing the benefits of ‘open frame low to
medium DC/DC converters’ Design Note 102 is available from
Artesyn Technologies. The effective elimination of potting and a case
has been made possible by the use of modern automated
manufacturing techniques and in particular the 100% use of SMT
components, the use of planar magnetics and the exceptionally high
efficiencies.
4. Features and Functions
4.1 Wide Operating Temperature Range
The wide ambient operating temperature range of the EXB50 Dual
module is a result of the extremely high power conversion efficiency
and resultant low power dissipation. The maximum ambient
temperature at which the module can be operated depends on a
number of parameters, such as:
• the target application input voltage range
• the output voltage set-points, which can be varied over an ultra-
wide range of 1.5V to 5.25V
• the output load currents
• if present, air velocity in a forced air convection environment
• mounting orientation of target application pcb, i.e. vertical or
horizontal mount (especially important in natural convection
conditions)
• target application pcb design, especially ground planes which can
be effective heastsinks for the power converter
In a typical application the EXB50 Dual can deliver up to 5A at each
output in a natural convection, -40°C to +70°C environment.
A number of design graphs are included in the long-form datasheet.
They simplify the design task and allow the power system designer
to determine the maximum local ambient temperature at which the
EXB50 Dual module may be operated, for a given set of application
conditions. A chapter of this application note is dedicated to two
design examples demonstrating the use of these design graphs.
4.2 Over-Temperature Protection
The EXB50 Dual converters are equipped with a non-latching over-
temperature protection. A temperature sensor monitors the
temperature of the main substrate. If the temperature exceeds a
threshold of 125°C (typical) the converter will shut down disabling
both outputs. When the substrate temperature has decreased by
10°C (typical), the converter will automatically restart.
The EXB50 Dual converter might experience over-temperature
conditions in case of a persistent over-load on one or both outputs.
Over-load conditions can be caused by exter nal faults. OTP might
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3
Application Note 127
2.5A
2.5A
5.0A
5.0A
7.5A
7.5A
10A
10A
lo2
lo1
Safe
Operating
Area
EXB50-48D05-3V3
Current Limit Inception
the trim pin and the positive output will trim the output voltage down.
A resistor between the trim pin and the negative output will trim the
output voltage up. A trim pot with its terminals connected to the
positive and negative outputs, and the wiper connected to the trim
pin, allows a variable trim, either up or down. This is shown in Figure
4 and Figure 5.
Figure 3a - Control Input Drive Circuits, Non-Isolated Bipolar
Figure 3b - Control Input Drive Circuits, Logic Driver
Figure 3c - Control Input Drive Circuits, Isolated through
Optocoupler
transient overload conditions are acceptable (e.g. start-up into
capacitive loads), permanent overload operation is not. Permanent
overload conditions can reduce the lifetime of the converter, and the
unit may suffer permanent damage.
If Io(total) exceeds the current limit threshold for a time period of
>20ms, the converter will shut down for 200ms. After 200ms the
converter will start up again. For a persistent overload condition the
converter will work in a low-frequency hiccup mode with an ON time
of 20ms and an OFF time of 200ms. In hiccup mode the hiccup
frequency is 1/220ms=4.5Hz with a hiccup duty cycle of
20ms/220ms=9%. Hiccup mode operation greatly reduces the
thermal stress of the converter, protects wiring and load, and
increases system reliability.
In short circuit operation the converter also enters a low-frequency
hiccup mode. The RMS value of the pulsating output current in short
circuit operation is limited to 15A maximum, simplifying the design of
external crowbar circuits. While the unit is specified to operate into a
continuous short circuit, frequent short circuits will reduce the
lifetime of the converter.
4.6 Remote ON/OFF
The control input allows external circuitry to put the EXB50 Dual
converter into a low dissipation sleep mode. The control input is
sometimes also referred to as a remote ON/OFF input. Preferred, and
by default, EXB50 Dual converters provide an active-high control
input, but are also available with active-low logic.
Table 2 lists the converter operating condition (enabled or disabled)
vs. control pin logic level for both logic options. The signal level of
the control input is defined with respect to Vin-.
Table 2 - Remote ON/OFF Configuration
To simplify the design of the exter nal control circuit, logic signal
thresholds are specified over the full temperature range. The
maximum control input open circuit voltage, as well as the
acceptable leakage currents are specified.
The control input can be driven in a variety of ways as shown in
Figure 3. If the control signal originates on the primary side, the
control input can be driven through a discrete device (e.g. a bipolar
signal transistor), or directly from a logic gate output. The output of
the logic gate may be an open-collector (or open-drain) device.
If the drive signal originates on the secondary side, the control input
can be isolated and driven through an optocoupler.
4.7 Output Voltage Adjustment
The ultra-wide output voltage trim range offers major advantages to
users of the EXB50 Dual. It is no longer necessary to purchase a
variety of modules in order to cover different output voltages. Both
output voltages can be trimmed in a range of 1.5V to 5.25V. No
relative restrictions apply, i.e. Vo1can be higher or lower than Vo2.
When the EXB50 Dual converter leaves the factory the outputs have
been adjusted to the following default voltages: Vo1=5.0V and
Vo2=3.3V
Both output voltages can be independently adjusted using resistors.
One trim pin per output is provided. Connecting a resistor between
4
EXB50 Dual SERIES |Application Note 127 Rev. 02
Control
V01 +
EXB50
Dual V01 -
Trim1
V02 +
V02 -
Trim 2
Vin+
Vin-
Control
V01 +
EXB50
Dual V01 -
Trim1
V02 +
V02 -
Trim 2
Vin+
Vin-
Control
V01 +
EXB50
Dual V01 -
Trim1
V02 +
V02 -
Trim 2
Vin+
Vin-
Control Input
Logic Type Low High Floating
Positive (Default) Disabled Enabled Enabled
Negative (-R option) Enabled Disabled Disabled
Figure 4a - Trimming Output Voltage Vo1, Trim Up
Figure 4b - Trimming Output Voltage Vo1, Trim Down
Figure 4c - Trimming Output Voltage Vo1, Variable Trim
www.artesyn.com
5
Application Note 127
Control
V01+
EXB50
Dual V01-
Trim1
V02+
V02-
Trim2
Vin+
Vin-
Figure 5a - Trimming Output Voltage Vo2, Trim Up
Figure5b - Trimming Output Voltage Vo2, Trim Down
Figure5c - Trimming Output Voltage Vo2, Variable Trim
Suitable standard E96 series resistor values for all possible output
voltages in 0.1V increments can be found in Table 3. Note that if the
desired output voltage Vo1=5.0V no trim resistor is required. The
same applies if Vo2=3.3V. These are the factory preset values.
Control
V01 +
EXB50
Dual V01 -
Trim1
V02 +
V02 -
Trim 2
Vin+
Vin-
Control
V01+
EXB50
Dual V01-
Trim1
V02+
V02-
Trim2
Vin+
Vin-
Control
V01+
EXB50
Dual V01-
Trim1
V02+
V02-
Trim2
Vin+
Vin-
Control
V01 +
EXB50
Dual V01 -
Trim1
V02 +
V02 -
Trim 2
Vin+
Vin-
Control
V01+
EXB50
Dual V01-
Trim1
V02+
V02-
Trim2
Vin+
Vin-
provided in Figures 6 to 8. Trim graphs are given for resistive
trimming, as well as voltage trimming. The output voltages Vo1and
Vo2can be trimmed by applying a voltage to the respective trim pins
Trim1 and Trim2. Trim voltages are referenced to the output return
pins Vo1- and Vo2-.
For all other trim requirements please contact Artesyn Technologies
for advice.
Figure 6a - Typical Trim Curve Vo1 Trim up Resistive
Figure 6b - Typical Trim Curve Vo1 Trim Down Resistive
Figure 7a - Typical Trim Curve Vo2 Trim up Resistive
EXB50 Dual SERIES |Application Note 127 Rev. 02
6
Table 3 - Recommended Trim Resistor Values for Various
Output Voltage Setpoints
If other output voltages are required, various trim graphs are
Vo Rtrim1 (Vo1) Rtrim2 (Vo2)
1.5V 7.5ΩTrim1 to Vo1+ 35.7ΩTrim2 to Vo2+
1.6V 17.4ΩTrim1 to Vo1+ 78.7ΩTrim2 to Vo2+
1.7V 28ΩTrim1 to Vo1+ 124ΩTrim2 to Vo2+
1.8V 39.2ΩTrim1 to Vo1+ 178ΩTrim2 to Vo2+
1.9V 51.1ΩTrim1 to Vo1+ 243ΩTrim2 to Vo2+
2.0V 63.4ΩTrim1 to Vo1+ 309ΩTrim2 to Vo2+
2.1V 76.8ΩTrim1 to Vo1+ 392ΩTrim2 to Vo2+
2.2V 90.9ΩTrim1 to Vo1+ 487ΩTrim2 to Vo2+
2.3V 107ΩTrim1 to Vo1+ 604ΩTrim2 to Vo2+
2.4V 124ΩTrim1 to Vo1+ 750ΩTrim2 to Vo2+
2.5V 140ΩTrim1 to Vo1+ 931ΩTrim2 to Vo2+
2.6V 162ΩTrim1 to Vo1+ 1150ΩTrim2 to Vo2+
2.7V 182ΩTrim1 to Vo1+ 1470ΩTrim2 to Vo2+
2.8V 205ΩTrim1 to Vo1+ 1910ΩTrim2 to Vo2+
2.9V 232ΩTrim1 to Vo1+ 2550ΩTrim2 to Vo2+
3.0V 261ΩTrim1 to Vo1+ 3650ΩTrim2 to Vo2+
3.1V 287ΩTrim1 to Vo1+ 5760ΩTrim2 to Vo2+
3.2V 324ΩTrim1 to Vo1+ 12.1kΩTrim2 to Vo2+
3.3V 365ΩTrim1 to Vo1+ -
3.4V 402ΩTrim1 to Vo1+ 3480ΩTrim2 to Vo2-
3.5V 453ΩTrim1 to Vo1+ 1650ΩTrim2 to Vo2-
3.6V 511ΩTrim1 to Vo1+ 1050ΩTrim2 to Vo2-
3.7V 576ΩTrim1 to Vo1+ 732ΩTrim2 to Vo2-
3.8V 649ΩTrim1 to Vo1+ 549ΩTrim2 to Vo2-
3.9V 732ΩTrim1 to Vo1+ 432ΩTrim2 to Vo2-
4.0V 845ΩTrim1 to Vo1+ 348ΩTrim2 to Vo2-
4.1V 976ΩTrim1 to Vo1+ 280ΩTrim2 to Vo2-
4.2V 1130ΩTrim1 to Vo1+ 226ΩTrim2 to Vo2-
4.3V 1330ΩTrim1 to Vo1+ 187ΩTrim2 to Vo2-
4.4V 1620ΩTrim1 to Vo1+ 154ΩTrim2 to Vo2-
4.5V 2000ΩTrim1 to Vo1+ 127ΩTrim2 to Vo2-
4.6V 2550ΩTrim1 to Vo1+ 105ΩTrim2 to Vo2-
4.7V 3480ΩTrim1 to Vo1+ 84.5ΩTrim2 to Vo2-
4.8V 5360ΩTrim1 to Vo1+ 66.5ΩTrim2 to Vo2-
4.9V 10.7kΩTrim1 to Vo1+ 51.1ΩTrim2 to Vo2-
5.0V - 37.4ΩTrim2 to Vo2-
5.1V 221ΩTrim1 to Vo1- 25.5ΩTrim2 to Vo2-
5.2V 61.9ΩTrim1 to Vo1- 14.7ΩTrim2 to Vo2-
1
1
5.2
5.1
5
5.3
5.4
10 100 1·1031·1041·105
1x105
TRIM UP RESISTOR (kΩ)
5.007
5.332
Vo1_trimup (Rtrimi)
% INCREASE IN Vout
1
1
4
3.5
3
4.5
5
5.5
10 100 1·1031·1041·105
1x105
TRIM UP RESISTOR (kΩ)
3.303
5.346
Vo2_trimup (Rtrimi)
% INCREASE IN Vout
1
1
3
2
1
4
5
10 100 1·1031·1041·105
1x105
TRIM DOWN RESISTOR (kΩ)
1.43
4.995
Vo1_trimdn (Rtrimi)
% INCREASE IN Vout
Insulation
Between And
TNV-1 Circuit Earthed SELV Circuit
Unearthed SELV Circuit
TNV-2 Circuit Earthed SELV Circuit
TNV-3 Circuit Unearthed SELV Circuit or
TNV-1 Circuit
Earthed or Unearthed Earthed SELV Circuit
Hazardous Voltage ELV Circuit
Secondary Circuit Unearthed Hazardous
Voltage Secondary Circuit
TNV-1 Circuit
5. Safety
5.1 Isolation
The EXB50 Dual series has been submitted to independent safety
agencies and has EN60950 and UL1950 Safety approvals. Basic
insulation is provided and the unit is approved for use between the
classes of circuits listed in Table 4.
Table 4 - Insulation Categories for Basic
The TNV or Telecommunication Voltage definitions are given in Table
V.1 of IEC950 from which EN60950 and UL1950 are derived.
The EXB50 Dual has an approved insulation system that satisfies the
requirements of the safety standards.
In order for the user to maintain the insulation requirements of these
safety standards it is necessary for the required creepage and
clearance distances to be maintained between the input and output.
Creepage is the distance along a surface such as a PCB and for the
EXB50 the creepage requirement between primary and secondary is
1.4mm or 55 thou. Clearance is the distance through air and the
requirement is 0.7mm or 27 thou.
5.2 Input Fusing
In order to comply with safety requirements the user must provide a
fuse in the unearthed input line if an earthed input is used. The
reasons for putting the fuse in the unearthed line is to avoid earth
being disconnected in the event of a failure. If an earthed input is not
being used the fuse may be in either input line.
The recommended fuse rating for the EXB50 Dual converter is 4A,
HRC (High Rupture Capacity), anti-surge, rated for 200V.
6. EMC
The EXB50 Dual has been designed to comply with the EMC
requirements of ETSI 300 386-1. It meets the most stringent
requirements of Table 5, public telecommunications equipment,
locations other than telecommunication centres, high priority of
service. The following sections detail the list of standards which
apply, and with which the product complies.
Application Note 127
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7
Figure 7b - Typical Trim Curve Vo2 Trim Down Resistive
Figure 8a - Typical Trim Curve Vo1 for Trimming by Application
of a Trim Voltage to the Trim Pin
Figure 8b - Typical Trim Curve Vo2 for Trimming by Application
of a Trim Voltage to the Trim Pin
1
1
2
1.5
1
2.5
3
3.5
10 100 1·1031·1041·105
1x105
TRIM DOWN RESISTOR (kΩ)
1.407
3.287
Vo2_trimdn (Rtrimi)
% INCREASE IN Vout
% Vout
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
1.5
0
1
2
3
4
5
6
5.336
1.195
Vo1_trimsrc (Vtrim)
TRIM VOLTAGE (V)
% Vout
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
1.5
0
1
2
3
4
5
6
5.357
1.135
Vo2_trimsrc (Vtrim)
TRIM VOLTAGE (V)
EXB50 Dual SERIES |Application Note 127 Rev. 02
8
6.1 Conducted Emissions
The applicable standard for conducted emission is EN55022 (FCC
Part 15). The EXB50 Dual has a substantial second order filter on
board to enable it to meet this standard using a simple external filter.
Figure 9 - Recommended External Input Filter
Conducted emission measurement results are shown in Figure 10.
The results were obtained using the recommended external input
filter
Figure 10 - Typical Spectrum EXB50-48D05-3V3
(Vin=48V, Vo1=5.0V, Io1=5A, Vo2=3.3V, Io2=5A)
50µH LISN. Class A and B Average Limit Lines Shown
6.2 Radiated Emissions
The applicable standard is EN55022 Class B (FCC Part 15). Testing
DC/DC converters as a stand-alone component to the exact
requirements of EN55022 (FCC Part 15) is very difficult to do as the
standard calls for 1m leads to be attached to the input and output
ports and aligned such as to maximise the disturbance. In such a
set-up it is possible to form a perfect dipole antenna that very few
DC/DC converters could pass.
However the standard also states that 'An attempt should be made
to maximise the disturbance consistent with the typical application
by varying the configuration of the test sample'. In addition, ETS 300
386-1 states that the testing should be carried out on the enclosure.
The EXB50 Dual is primarily intended for PCB mounting in
telecommunication rack systems.
For the purpose of the radiated test, an EXB50-48D05-3V3 was
mounted on a 6U high test-board using the recommended PCB
layout (see Appendix 1). The operating conditions were:
• Input voltage Vin=48V
• Output voltage Vo1=5.0V (factory default)
• Output voltage Vo2=3.3V (factory default)
• Output current Io1=5A
• Output current Io2=5A
• Ambient temperature Tamb=25°C
No enclosure was used. Typical radiated emission results are
presented in Figure 11.
Figure 11 - Typical Radiated Emission EXB50-48D05-3V3
(Vin=48V, Io1=5A, Io2=5A)
It can be seen that the EXB50 Dual converter comfortably meets the
EN55022 Limit A even without an enclosure.
6.3 Common Mode Noise
This is generated in switching converters and can contribute to both
radiated emissions and input conducted emissions. The EXB50 Dual
series of converters bypasses common mode noise internally by
using a 2.2nF capacitor between input ground and output ground.
The EXB50 Dual series will therefore greatly minimise common mode
noise currents flowing in the application circuitry.
7. Use in a Manufacturing Environment
7.1 Resistance to Soldering Heat
The EXB50 Dual series are intended for PCB mounting. Artesyn has
determined how well it can resist the temperatures associated with
the soldering of PTH components without affecting its performance
or reliability. The method used to verify this is MIL-STD-202 method
210D. Within this method two test conditions were specified,
Soldering Iron condition A and Wave Solder condition C.
For the soldering iron test the UUT was placed on a PCB with the
recommended PCB layout pattern shown in the applications section.
A soldering iron set to 350°C ± 10°C was applied to each terminal
for 5 seconds. The UUT was then removed from the test PCB and
was examined under a microscope for any reflow of the pin solder or
physical change to the terminations. None was found.
MMG Bead
W524Y3Y-0M01E0T
8 x
AVX 470nF, 100V
X7R, 10%
1812C474KAT1A
8 x
AVX 470nF, 100V
X7R, 10%
1812C474KAT1A
TDK 22uH, 1.9A
SLF10145T
-220M1R9
5Ω
100mW
TDK 27uH
NL45232-270J
DC
Source EXB50
Dual
++
--
FREQUENCY (MHz)
AMPLITUDE (dBuV/m)
0 100 200 300
0
10
20
30
40
50
EN55022 Limit Class A
EN55022 Limit Class B
EXB50-48D05-3V3
Temperature Time Temperature Ramp
260°C ±5°C 10s±1 Preheat 4°C/s to 160°C.
25mm/s rate
Application Note 127
www.artesyn.com
9
For the wave soldering test the UUT was again mounted on a test
PCB. The unit was wave soldered using the conditions shown in
Table 5.
Table 5 - Wave Solder Test Conditions
The UUT was inspected after soldering and no physical change on
pin terminations was found.
7.2 Water Washing
The EXB50 Dual is suitable for water washing as it doesn’t have any
pockets where water may congregate long-term. The user should
ensure that a sufficient drying process and period is available to
remove the water from the unit after washing
7.3 ESD Control
The EXB50 Dual units are manufactured in an ESD controlled
environment and supplied in conductive packaging to prevent ESD
damage occurring before or during shipping. It is essential that they
are unpacked and handled using an approved ESD control
procedures. Failure to do so could affect the lifetime of the converter.
8. Applications
8.1 Optimum PCB Layout
A recommended PCB layout for a two-layer board can be found in
Appendix 1. Although internally connected, it is recommended that a
common secondary ground plane be used, connecting Vo1- and Vo2-
This will result in improved efficiency, reduced output noise, and
reduced radiated noise.
For compliance with safety regulations there are certain keep-out
areas on the top-side (facing the EXB50 Dual converter) of the user
board. Typically, for basic insulation a clearance of 0.7mm is
required. The recommended footprint and layout of the user board is
shown in Appendix 1. Three keep-out areas are shown and
dimensioned on the top side of the layout.
8.2 Optimum Thermal Performance
The electrical operating conditions of the EXB50 Dual converters:
• input voltage Vin
• output voltage set-points Vo1and Vo2(trimmable from 1.5V
to 5.25V each)
• output currents Io1and Io2
determine how much power is dissipated within the converter.
Together with the environmental operating conditions:
• ambient temperature
• air velocity
they will result in a particular device temperature of the converter.
The maximum acceptable device temperature measured at the
thermal reference points is 110°C. The thermal reference points are
shown in Figure 12.
Figure 12 - Thermal Reference Points
To simplify the thermal design task a number of graphs are given in
the datasheet. A set of power dissipation graphs show the power
dissipation of the EXB50 Dual converter versus the input voltage.
These graphs cover the most popular output voltage combinations
(5.0V/3.3V, 3.3V/2.5V, 3.3V/1.8V, 2.5V/1.8V). Parameters in all of
these graphs are the load combinations Io1/Io2covering popular
representative load combinations 5.0A/5.0A, 7.5A/2.5A, 2.5A/7.5A,
7.5A/7.5A and 2.5A/2.5A.
For all other custom output voltage set-points, and different load
combinations interpolation can be used to estimate the power
dissipation. Alternatively please contact Artesyn Technologies for
further support.
For a given electrical operating condition the estimation of the
maximum operating ambient temperature of the EXB50 Dual
converter is a two-step process:
• Determine the maximum power dissipation of the converter using
the appropriate power dissipation graph given in the datasheet
• Determine the maximum operating ambient temperature using the
appropriate graph given in the datasheet.
The following design examples demonstrate this process.
8.3 Design Examples
Design Example 1
• Input voltage range 40V to 60V
• Output voltage Vo1=5.0V (factory default)
• Output voltage Vo2=3.3V (factory default)
• Output current Io1=7.5A
• Output current Io2=2.5A
• Natural convection
Question: What's the maximum ambient temperature at which the
converter can be operated?
Step 1: Determination of the maximum power dissipation.
In the datasheet, refer to the graph "Power dissipation versus input
voltage" for the output voltage combination Vo1=5.0V and Vo2=3.3V.
This graph is reproduced in Figure 13. This graph shows the power
dissipation versus input voltage for different output current
combinations. It can be seen that for the electrical operating
condition of design example 1 the worst case power dissipation is
approximately 6.5W at an input voltage of Vin=60V.
Thermal Ref #1
Thermal Ref #3
Thermal Ref #4
Thermal Ref #5
Thermal Ref #2
EXB50 Dual SERIES |Application Note 127 Rev. 02
10
Figure 13 - Example 1 - Step 1: Determination of Power
Dissipation (Vo1=5.0V, Vo2=3.3V)
Step 2: Determination of the maximum ambient operating
temperature
In the datasheet, refer to the graph "Maximum ambient temperature
versus power dissipation". This graph is again reproduced in Figure
14. For a power dissipation of 6.5W and an air velocity of 0.0m/s
(natural convection), the maximum ambient operating temperature is
59°C.
Figure 14 - Example 1. Step 2: Determination of the Maximum
Ambient Operating Temperature
Answer: For an input voltage range of Vin=40V to 60V, and
Vo1=5V/Io1=7.5A, Vo2=3.3V/Io2=2.5A, natural convection, the
maximum ambient operating temperature is 59°C.
Design Example 2
• Input voltage range 36V to 75V
• Output voltage Vo1=3.3V
• Output voltage Vo2=2.5V
• Output current Io1=7.5A
• Output current Io2=7.5A
• Maximum ambient temperature Tamb=50°C
Question: Is forced air convection required? If so, what's the
required air velocity?
Step 1: Determination of the maximum power dissipation.
The required data sheet graph of power dissipation for output
voltage combination 3.3V/2.5V is reproduced in Figure 15. The worst
case power dissipation of Pdiss=10.0W occurs at the maximum
input voltage Vin=75V.
Figure 15 - Example 2 - Step 1: Determination of Power
Dissipation (Vo1=3.3V, Vo2=2.5V)
Step 2: Determination of the required air velocity for forced air
convection.
Refer to the graph "Maximum ambient temperature versus power
dissipation". The graph is shown in Figure 16. It can be seen that for
a power dissipation of 10.0W, and an ambient temperature of 50°C,
forced air convection is necessary. An air velocity of 1.0m/s is
adequate, and will leave a small amount of thermal headroom.
Figure 16 - Example 2 - Step 2: Determination of the
Required Air Velocity
Answer: For an input voltage range of Vin=36V to 75V,
Vo1=3.3V/Io1=7.5A, Vo2=2.5V/Io2=7.5A, and a maximum ambient
operating temperature of 50°C, forced air convection is required. The
required air velocity is vair=1.0m/s.
It should be noted that in a complex thermal setup the definition of
ambient temperature can be ambiguous. The local ambient
temperature seen by the converter may be considerably higher than
the system ambient temperature. Also the local air velocity may
deviate considerably. It is therefore absolutely essential to verify in
the target system that all temperature reference points are within
their specification of 110°C. Exposure of the EXB50 Dual converters
to higher temperatures can cause permanent damage to the device.
As shown in Figure 12 there are five thermal reference points on the
EXB50 Dual. Depending on the electrical operating conditions, any
one of the thermal reference points may be the hottest. However, the
36
4
2
0
6
8
10
12
44 52 60 68 76
POWER DISSIPATION (W)
INPUT VOLTAGE (V)
7.5A/7.5A
7.5A/2.5A
2.5A/2.5A
2.5A/7.5A
5A/5A
3.5
50
40
30
60
70
80
90
5.5 7.5 9.5 11.5 13.5
TAMB MAX (ºC)
POWER DISSIPATION (W)
2.0 m/s
2.5 m/s
0 m/s
0.5 m/s
1.0 m/s
1.5 m/s
36
4
2
0
6
8
10
12
44 52 60 68 76
INPUT VOLTAGE (V)
7.5A/7.5A
7.5A/2.5A
2.5A/2.5A
2.5A/7.5A
5A/5A
POWER DISSIPATION (W)
3.5
50
40
30
60
70
80
90
5.5 7.5 9.5 11.5 13.5
TAMB MAX (ºC)
POWER DISSIPATION (W)
2.0 m/s
2.5 m/s
0 m/s
0.5 m/s
1.0 m/s
1.5 m/s
Application Note 127
www.artesyn.com
11
temperatures of the reference points will typically be within 10°C of
each other. It is recommended to measure the temperature of the
reference points using thermocouples or an IR camera. In order to
comply with the stringent Artesyn Derating Criteria none of the
thermal reference temperatures should ever exceed 110°C.
8.4 Active Inrush Current Limiting
To allow safe insertion and removal of a circuit card from a live
backplane, the inrush current of the card has to be limited. A
recommended active inrush current limiting circuit is shown in Figure
17. The circuit provides a programmable inrush current limit and a
programmable electronic circuit breaker. Please refer to the
datasheet of the LT1640L for detailed information.
The EXB50 Dual comes with its own internal UV lockout feature.
Therefore components R4, R5, R6, R7 and Q2 are required only if the
UV threshold of the EXB50 Dual is to be increased, or additional OV
protection is required. The recommended value for R7 is 200kΩ.
Circuit block XF1 consists of the recommended input filter (see
section Conducted Emissions), hold-up and impedance stabilising
capacitors.
8.5 Parallel and Series Operation
Because of the absence of an active current sharing feature, parallel
operation of multiple EXB50 Dual converters is generally not
recommended. If unavoidable, Oring-diodes must be used to
decouple the outputs. Droop resistors will support some passive
current sharing. It should be noted that both measures will adversely
affect the power conversion efficiency.
Outputs of multiple EXB50 Dual converters can be connected in
series. Note, however, that the two outputs of an individual EXB50
Dual converter are not isolated from each other, and cannot be
connected in series with each other. The grounds are connected
internally (i.e. Vo1- is connected to Vo2-).
Figure 17 - Recommended Inrush Current Limiting Circuit
8.6 Output Noise and Ripple Measurement
The circuit in Figure 18 has been used for noise measurement on
EXB50 Dual series converters. The large toroid will act as a common
mode filter to noise which would otherwise flow through the
measuring instrument or oscilloscope to disturb the measurement of
the differential mode noise.
A 50Ωcoax lead should be used with source and termination
impedances of 50Ω. This will prevent impedance mismatch
reflections which would otherwise disturb the noise reading at higher
frequencies.
The 50Ωresistor which is added in series with the output of the
power supply will form a voltage divider with the termination 50Ω
and so ripple and noise measurement readings should be multiplied
by 2.
System
GND
R4 UV
OV
VEE Sense Gate Drain
PWRGD
VDD
R1
R2
R3
R7
C2
C1
Q1 Q2
Remote
on/off
Vin+
Vin-
Vo2+
Vo2-
Trim2
Vo1+
Vo1-
Trim1
XF1
R5
R6
System
-Vin
(e.g. -48V)
LT1640L
EXB50
Dual
Vout+
Vout-
50Ω
100nF Low Loss, Low Inductance Type Capacitor
50Ω Coax
Low Inductive
Type Resistor
TX36/23/15
3E25 Material
High µ Ferrite Torroid
5 Turns or More
Low Inductive
Type Resistor
50ΩMeasuring
Instrument/
Oscilloscope
NOTE: Readings must
be multiplied by 2
Figure 18 - Output Noise and Ripple Set-up
EXB50 Dual SERIES |Application Note 127 Rev. 02
12
Appendix 1 - Recommended PCB Footbprints
Figure 19a - Recommended Top Side Footprint (layer 1 of 2)
ALL DRAWINGS ARE VIEWED FROM THE TOP SIDE
FOR THERMAL RELIEF IN CONDUCTOR PLANES
REFERENCE IPC-D-275 SECTION 5.3.2.3
ALL DIMENSIONS IN INCHES (mm)
ALL TOLERANCES ARE ±0.10 (0.004)
Figure 19b - Recommended Bottom Side Footprint (Layer 2 of 2)
0.079 [2.00]
0.969 [24.62]
VIN+ TRIM 1
VO1-
VO1+
TRIM 2
VO2-
VO2+
VIN-
REM
0.327 [8.31]
2.128 [54.04]
1.828 [46.44]
1.511 [38.37]
0.515 [13.07]
2.400 [60.97]
0.563 [14.31]
0.633 [16.09]
2.280 [57.91]
C
L
C
L
0.079 [2.00]
VIN+ TRIM 1
VO1-
VO1+
TRIM 2
VO2-
VO2+
VIN-
REM
2.396 [60.85]
0.079 [2.00]
2.280 [57.91]
C
L
C
L
