1. Introduction
The EXB30 series is a new generation of DC/DC converters which
were designed in response to the growing need for low operating
voltage and higher efficiencies. They offer unprecedented efficiency
figures and a wide range of low output voltage solutions.
In addition the automated manufacture methods and use of planar
magnetics together with an extensive qualification program have
produced one of the most reliable range of converters on the
market.
2. Models and Features
The EXB30 series comprises five separate models as shown in
Table 1. All popular integrated circuit operating voltages are covered
by the entire range.
Table 1 - EXB30 Models
Features
• Industry standard half-brick pinout and footprint:
61.0 x 57.9 x 10.9mm (2.40 x 2.28 x 0.43 inches)
• Wide operating ambient temperature range of -40˚C to +85˚C
• Output voltage adjustability
• Remote sense compensation
• Primary-side controlled remote on/off
• Constant switching frequency
• Brickwall overcurrent protection
• Continuous short circuit protection
• Overtemperature protection
• Output overvoltage protection
• Input undervoltage and overvoltage protection
EXB30 SERIES
Application Note 108 Rev. 02 - July 2000
• Ultra high efficiency topology, 92% typical at 5V
• Operating ambient temperature of -40°C to +85°C (natural
convection)
• Approved to EN60950, UL/cUL1950
• Complies with ETS 300 019-1-3/2-3
• Complies with ETS 300 132-2 input voltage and current
requirements
• Fully compliant with ETS 300 386-1
• Basic insulation (input to output)
• Industry standard half-brick pin-out
PAGE 1
1. Introduction . . . . . . . . . . . . . . . . . . . . . .1
2. Models and Features . . . . . . . . . . . . . .1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3. General Description . . . . . . . . . . . . . . .2
Electrical Description . . . . . . . . . . . . . . . . . . . .2
Physical Construction . . . . . . . . . . . . . . . . . . .2
4. Features and Functions . . . . . . . . . . . .2
Wide Operating Temperature Range . . . . . . . . .2
Remote Sense Compensation . . . . . . . . . . . . .2
Output Voltage Adjustment . . . . . . . . . . . . . . .2
Remote On/Off . . . . . . . . . . . . . . . . . . . . . . . .2
Constant Switching Frequency . . . . . . . . . . . .3
Brickwall Current Limit and Short Circuit Prot. .3
Over Temperature Protection . . . . . . . . . . . . . .3
Output Overvoltage Protection . . . . . . . . . . . . .3
Input Undervoltage and Overvoltage Protection3
5. Safety . . . . . . . . . . . . . . . . . . . . . . . . . .4
Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Input Fusing . . . . . . . . . . . . . . . . . . . . . . . . . . .4
6. EMC . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Radiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Conducted . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
7. Use in a Manufacturing Environment . .6
Resistance to Soldering Heat . . . . . . . . . . . . . .6
Water Washing . . . . . . . . . . . . . . . . . . . . . . . . .6
ESD Control . . . . . . . . . . . . . . . . . . . . . . . . . . .6
8. Applications . . . . . . . . . . . . . . . . . . . . .6
Optimum PCB Layout . . . . . . . . . . . . . . . . . . .6
Optimum Thermal Performance . . . . . . . . . . . .7
Remote ON/OFF Control . . . . . . . . . . . . . . . . .8
Positive Logic . . . . . . . . . . . . . . . . . . . . . . . . .8
Specification for the Remote On/Off . . . . . . . .8
Isolated Closure Remote On/Off . . . . . . . . . . .8
Level Controlled Remote On/Off . . . . . . . . . . .8
Remote Sense Compensation . . . . . . . . . . . . .8
Output Voltage Adjustment . . . . . . . . . . . . . . .9
Output Capacitance . . . . . . . . . . . . . . . . . . . . . 9
Output Noise and Ripple Measurement . . . . .10
Compatibility with Hot Swap Controller . . . . .11
Model Input Voltage Output Voltage
EXB30-48S05 36-75VDC 4.0V to 5.5V
EXB30-48S3V3 36-75VDC 2.64V to 3.63V
EXB30-48S2V5 36-75VDC 2.0V to 2.75V
EXB30-48S2V0 36-75VDC 1.6V to 2.2V
EXB30-48S12 36-75VDC 7.2V to 13.2V
NEW
Product
In the low voltage models the rectification stage consists of
synchronous rectifiers that are controlled by proprietary circuitry on
the secondary side which optimise the driving scheme for high
efficiency power conversion. The rectification stage for the 12V
model consists of schottky diodes.
Physical Construction
The EXB30 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.
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
Wide Operating Temperature Range
The wide ambient temperature range of the EXB30 module is a
consequence of the extremely high efficiency achieved and
consequent low power dissipation. Operation from -40˚C to a
maximum ambient temperature of +85˚C is achieved without the
requirement for heatsinks or forced air cooling, making the EXB30
ideally suited to cost and space sensitive applications.
Remote Sense Compensation
The EXB30 models have a remote sense feature to compensate for
moderate voltage drops in the distribution system. Thus accurate
voltage regulation can be achieved directly at the load terminals.
Further details concerning the remote sense compensation feature
are presented in the applications section.
Output Voltage Adjustment
The output voltage on the 2V, 2.5V, 3.3V and 5V models is trimmable
by -20% to +10% of the nominal output voltage. The 12V output
voltage can be trimmed by -40% to +10%. Details on how to trim
all models are provided in the applications section.
3. General Description
Electrical Description
The EXB30 power module is a DC/DC converter that operates over
an input voltage range of 36VDC to 75VDC and provides an isolated
regulated DC output. The modules have maximum power ratings of
30W and excellent efficiencies are achieved by optimum driving of
the synchronous rectification stage. The standard feature set
includes remote on/off, remote sense and output trim for maximum
flexibility in distributed power applications.
Figure 1 - Simplified Schematic
The DC input is filtered by an LC filter stage before it reaches the
main power transformer. A current controlled PWM controller is
used to provide a precisely regulated output voltage. The main
power switch is a MOSFET running at a constant switching
frequency of 300kHz approximately.
The output voltage at the sense pins of the module is sensed and
compared with a secondary side reference and a compensated error
signal is fed back via an optocoupler to the PWM controller. The
secondary side trim pin allows the user to adjust the output voltage
by connecting a resistor between trim and either the positive or
negative output voltage sense pin.
The output overvoltage clamp consists of a second control loop,
independent from the main regulation loop, that senses the voltage
on the output power pins. This OVP loop has typically a 15%
higher setpoint relative to the main loop. Further details on the OVP
feature can be found in the applications section.
An Over-Temperature Protection (OTP) circuit on the primary side
shuts down the PWM controller if the converter is in danger of being
damaged. There is typically 5˚C of thermal hysteresis which is used
to protect the unit.
The remote on/off function allows the user to disable the converter,
hence forcing the unit into a lower power dissipation mode.
The power transformer which is a planar construction uses the PCB
for the primary winding while SMT copper windings are used for the
secondary winding. Electrically, the transformer operates just the
same as a conventional transformer. However, the advantages of a
planar design are as follows:
• Excellent thermal characteristics
• Low leakage inductance
• Excellent repeatability properties
EXB30 SERIES |
Application Note 108
PAGE 2
http://www.artesyn.com
Input LC
Filter
OTP
PWM Control
OptoCoupler
OptoCoupler
Feedback &
Adjustability
OVP
Detection
Trim
Rectification
Stage
+
On/Off
Current
limit
None of the specifications are guaranteed when the unit is
operated in an overcurrent condition. The unit can be operated
continuously in this condition. However the lifetime of the unit will
be reduced.
Over Temperature Protection
This feature is included as standard in order to protect the converter
and the circuitry it powers from overheating in the event of a
runaway thermal condition such as a fan failure at high temperatures
or continuous operation above Tmax at full power.
Prolonged operation under short circuit conditions at high ambient
temperatures might also cause the OTP circuit to trip.
The actual ambient temperature it trips at is dependent on quite a
number of factors. The airflow over the unit is the most dominant
parameter. The trip point is also affected by the input voltage,
output trim voltage, user PCB layout, output load and model.
For all models under full load conditions the trip point will be at a
minimum ambient of 90°C in still air using the recommended layout
in the Applications section. Still air or natural convection is defined
as less than 0.1m/s airflow.
As the load is decreased and the unit is operated at higher
temperatures, the trip point also rises. This trip point will at all times
protect the unit and will be a minimum of 5°C within the safe
operating temperature of the device.
Output Overvoltage Protection
The clamped overvoltage protection (OVP) feature is used to protect
the module and the user’s circuitry when a fault occurs in the main
control loop. Faults of this type include optocoupler failure, blown
sense resistor or error amplifier failure. The unit is also protected in
the event that the output is trimmed above the recommended
maximum specification.
The OVP circuit consists of an auxiliary control loop running in
parallel to the main control loop using a separate optocoupler.
However, unlike the main loop, the OVP loop senses the voltage at
the output power terminals of the module, Vo+ and Vo-. The
sensed voltage is compared to a separate OVP reference and a
compensated error signal is generated such that the output voltage
is regulated to the OVP clamp level. The clamp levels are set quite
accurately and are given in Table 2.
Table 2 - OVP Trip Point
Input Undervoltage and Overvoltage Protection
The EXB30 series is fitted with a detection circuit at the input side
which inhibits operation of the converter when the input voltage is
outside the normal operating range. For 48V models, the converter is
disabled when the input voltage is below 32V or above 78V
approximately. The lower trip value protects against deep discharge
of telecom batteries while the upper level protects the module from
operating beyond the maximum input voltage rating. The thresholds
Remote On/Off
The Remote On/Off function allows the unit to be controlled by an
external signal which puts the module into a low power dissipating
sleep mode. Methods of using this function are given in the
applications section.
Constant Switching Frequency
The switching frequency for all models is fixed at approximately
300kHz and is independent of line and load levels. This makes the
overall power system more predictable and greatly simplifies the
design of the input filter required for EMC compliance.
Brickwall Current Limit and Short Circuit Protection
All models of the EXB30 have a built in brickwall current limit
function and full continuous short circuit protection. Thus, the V-I
(output voltage - output current) characteristic will be almost vertical
at the current limit inception point, as shown in Figure 2. A slight
tailout characteristic may be evident in some models when the
output voltage is reduced to very low values, i.e. under short circuit
conditions. A short circuit is defined as a resistance of 20mΩor
less.
Figure 2 - Typical Brickwall V-I Characteristic
The current limit inception point is dependent on the input voltage,
ambient temperature and has a parametric spread also. For all
models the inception point is typically 115% of rated full load. It
may go as high as 150% or as low as 100% over all operating
conditions and the lifetime of the product.
None of the specifications are guaranteed when the unit is operated
in an overcurrent condition. The unit will not be damaged in an
overcurrent condition as it will protect itself through the use of the
OTP function before any damage occurs. However the lifetime of
the unit may be reduced.
In a severe short circuit the unit may enter a ‘hiccup’ current mode
and may be operated continuously in this condition. The duty cycle
of this hiccup is dependent on input voltage, temperature etc.
While the unit is specified to operate into a continuous short circuit,
extended or frequent short circuits will reduce the lifetime of the
converter.
The current limit characteristic for the EXB30-48S12 is unlike that
for the low voltage models. The unit will exhibit brickwall current
limit for approximately 100ms after which the unit enters a hiccup
mode. The duty cycle of the hiccup depends on the level of
overcurrent. This mode of operation will continue indefinitely until
the overcurrent condition is corrected.
PAGE 3
EXB30 SERIES |
Application Note 108
Vout
Iout100%
Output Voltage Clamp Level
12V 14.2V
5V 5.6V
3.3V 3.8V
2.5V 3.0V
2.0V 2.3V
12.0V 14.2V
has complied with.
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 EXB30 is primarily intended for PCB mounting in
Telecommunication Rack systems.
For the purpose of the radiated test, an EXB30-48S3V3 was
mounted on a test PCB (230 x 170mm) with Vin- connected to a
copper ground plane on the PCB. A resistive load was connected
by lead lengths of approximately 10cm and the lead length to the
power source was 50cm. The unit was supplied with 48V input and
the output was 3.3V at 8A. The measurements were carried out at a
10m measurement distance on an open area test site using a Rhode
& Schwarz ESV receiver and a Farnell 352C Spectrum Analyser with
a Schwarzbeck BBA9106 broadband VHF antenna. An independent
test house performed the testing and a copy of the report is
available on request. The results of the test are given in Table 4. All
the responses were broadband in nature and there was no
detectable response above 147.41MHz. (The ‘V’ denotes the
antenna polarization for maximum response was Vertical). As
evident, Class A radiated emission requirements of EN55022 are
met with margin (limit is 40dBµV/m).
Table 4 - Radiated Emissions on EXB30-48S3V3 with Ground
Plane (within Class A limits)
Secondly, an external pi-filter was connected at the input to the unit,
details of which are given in Figure 5. The measured emission
levels are given in Table 5. There was no detectable response
above 146.54MHz. As evident, Class B radiated emission
requirements of EN55022 are met with margin (limit is 30dBµV/m).
also have inherent hysteresis to provide immunity against slow
ramping input voltages. The module operates in a low power
dissipation mode when protected.
5. Safety
Isolation
The EXB30 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 3.
Table 3 - 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 EXB30 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
EXB30 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.
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
reason 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 then the fuse may be in either input line.
A 2A HRC (High Rupture Capacity) is the recommended fuse rating
for the EXB30 product.
6. EMC
The EXB30 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. Following is the list of standards which apply and which it
PAGE 4
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EXB30 SERIES |
Application Note 108
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
Frequency (MHz) Response (dBµV/m) Limit (dBµV/m)
35.56 22.30V 40.00
42.28 25.60V 40.00
44.03 29.60V 40.00
48.34 21.30V 40.00
61.96 18.10V 40.00
78.88 20.20V 40.00
81.97 20.90V 40.00
109.62 27.40V 40.00
110.47 26.00V 40.00
147.41 35.30V 40.00
Table 5 - Radiated Emissions on EXB30-48S3V3 with Ground
Plane and External pi-filter (within Class B limits)
In both cases the unit passed the Class B limit which is 30 dBµV/m
with a significant margin.
Conducted emissions
The required standard for conducted emissions is EN55022 Class A
(FCC Part 15). The EXB30 has a substantial LC filter on board
which greatly reduces conducted emissions. However, to meet
Class A and Class B, external pi-filters are connected as described
in Figures 5 and 6 respectively. Putting these extra components on
board the EXB30 would have added to the cost and footprint of the
module. Additionally, this would have removed the flexibility that
end users have to add a single filter to the input of all converters on
a card thereby reducing cost and space.
The conducted noise plots for the EXB30-48S05 are shown in
Figures 3 and 4. The filter circuits to achieve these results are
shown in Figures 5 and 6. All other models have similar curves and
are available on request.
Figure 3 - Conducted Noise Measurements on
EXB30-48S05 (meets Class A average)
Figure 4 - Conducted Noise Measurements on
EXB30-48S05 (meets Class B average)
Figure 5 - Required Filter for Class A
Figure 6 - Required Filter for Class B
The part numbers for the parts used in each case are
given below:
C 470nF 100V AVX ceramic capacitor part number
18121C474KATMA
L1 47µH TDK inductor part number SLF10145T-470M1R4
L2 27µH Siemens inductor part number B82422-H1273-K100
R10Ω1206 1/4W resistor
Bead MMG SM Ferrite Bead part number B82422-H1273-K100
EXB30 SERIES |
Application Note 108
PAGE 5
CEXB30
C
L1
L2 R
CC
CEXB30
C
L1
L2 R
CCC C
0
10
20
30
40
50
60
70
80
dBµV
90
0.02 MHz
30
0.1 1 10
55022BAV
0
10
20
30
40
50
60
70
80
dBµV
90
0.02 MHz
30
0.1 1 10
55022AAV
Frequency (MHz) Response (dBµV/m) Limit (dBµV/m)
75.38 19.25V 30.00
81.20 21.20V 30.00
84.43 26.80V 30.00
116.78 24.50V 30.00
118.23 24.70V 30.00
119.99 25.95V 40.00
146.54 21.80V 30.00
7. Use in a Manufacturing Environment
Resistance to Soldering Heat
The EXB30 is 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.
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 8.
Table 8 - Wave Solder Test Conditions
The UUT was inspected after soldering and no physical change on
pin terminations was found.
Water Washing
The EXB30 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
ESD Control
The EXB30 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
Optimum PCB Layout
2Oz/ft2or 70µm copper should be used for connection to the pins.
The PCB acts as a heatsink and draws heat from the unit via
conduction through the pins and radiation. The two layers also act
as EMC shields. (The recommended layouts do not guarantee
system EMC compliance as this is dependent on the end
application). If the recommended layout or 2Oz/ft2copper isn’t used
then the user needs to ensure that the hot-spots highlighted in the
thermal section are kept within their limits.
These recommended PCB layouts will maintain the creepage and
clearance requirements discussed in the Safety section of this
application note. However, the end user must ensure that other
components and metal located in the vicinity of the EXB30 meet the
spacing requirements that the system is approved to.
VIEW IS FROM TOP SIDE
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 7 - Optimum PCB Layout for EMC and Thermals
for Single Outputs on a Single-Sided PCB
VIEW IS FROM TOP SIDE
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 8.1 - Optimum PCB Layout for EMC and Thermals
for Single Outputs on a Double-Sided PCB (Top)
EXB30 SERIES |
Application Note 108
PAGE 6
http://www.artesyn.com
Temperature Time Temperature Ramp
260°C ±5°C 10s±1 Preheat 4°C/s to 160°C.
25mm/s rate
ISOLATION
0.079 (2.00)
VIN+ VOUT+
VOUT-
VSENSE+
VSENSE-
TRIM
VIN-
0.292 (7.42)
1.204 (30.59)
2.280 (57.91)
TOP SIDE LAYER 1 OF 2
0.758 (19.26) 0.353 (8.97)
2.400 (60.97)
REM
C
L
C
L
ALL DIMENSIONS INCHES (MM)
2.280 (57.91)
2.400 (60.97)
ISOLATION
0.079 (2.00)
VIN+ VOUT+
VOUT-
VSENSE+
TRIM
VSENSE-
VIN-
REM
C
L
C
L
BOTTOM SIDE LAYER 2 OF 2
All DIMENSIONS INCHES (MM)
EXB30 SERIES |
Application Note 108
PAGE 7
VIEW IS FROM TOP SIDE
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 8.2 - Optimum PCB Layout for EMC and Thermals
for Single Outputs on a Double-Sided PCB (Bottom)
Figure 9 - Keep Out Areas on Top Side of User PCB
to Meet Safety Spacing Requirements
Optimum Thermal Performance
The EXB30 can operate in still air up to a maximum ambient
temperature of 85˚C using the recommended PCB layouts shown in
the previous section. Still air, which is sometimes called natural
convection is defined as <0.1m/s airflow (20CFM). The output
power may be derated so that the maximum ambient operating
temperature can be extended to 95°C as shown in Figure 10a. The
12V output is rated to supply an output current of 2.5A at an
operating ambient temperature of 85°C. At 80°C the output current
can be increased to 3.0A as shown in figure 10b.
Figure 10a - Output Power vs. Ambient Temperature
in Natural Convection for EXB30 series (Low Voltage Models)
Figure 10b - Output Power vs. Ambient Temperature
in Natural Convection for EXB30 12V model.
If forced air cooling is used then the converter may be used up to
95°C at full output power dependent on the airflow. Figure 11 is a
graph of the increased maximum ambient temperature at full power
versus the airflow across the converter.
Figure 11 - Increased Maximum Ambient Temperature
at Full Power with Forced Airflow
With an airflow of 1.5m/sec the allowed increase in ambient
temperature is 15˚C. Figure 12 shows the new derating curve for
the 48S05 model operating with 1.5m/s forced airflow.
-40˚C
0%
20%
40%
60%
80%
100%
Ambient Temperature
Rated Output Current
-20˚C0˚20˚C40˚C60˚C80˚C 100˚C
85˚C
ISOLATION
0.079 (2.00)
2.280 (57.91)
2.400 (60.96)
BOTTOM SIDE LAYER 2 OF 2
VIN+ VOUT+
VOUT-
VSENSE+
VSENSE-
TRIM
VIN-
REM
ISOLATION REQUIREMENTS FOR TOP SIDE (LAYER 1 OF 2)
2.030 (51.55)
0.436 (11.07)
1.218 (30.95)
1.497 (38.01)
1.743 (44.27)
2.042 (51.87)
SECONDARY CORE
SECONDARY CAPACITORS
SECONDARY CAPACITOR
PRIMARY / SECONDARY OPTOCOUPLER
All DIMENSIONS INCHES (MM)
PRIMARY CORE
CONVERTER OUTLINE
1.794 (45.57)
1.730 (43.95)
1.256 (31.90)
0.959 (24.36)
1.591 (40.41)
1.112 (28.23)
0.100 (2.54)
0.518 (13.16)
0.758 (19.26)
1.450 (36.83)
2.248 (57.09)
0.758 (19.26)
100% (3A)
-40°C
0%
80°C90°C
Rated Output Current
Ambient Temperature
Natural Convection (<0.1 m/s)
50% (1.5A)
83% (2.5A)
85°C
EXB30 SERIES |
Application Note 108
PAGE 8
http://www.artesyn.com
Figure 12 - Thermal Derating for 48S05 with 1.5m/s
Forced Airflow
For extreme environments the most accurate method of ensuring
that the converter is operating within its guidelines in a chosen
application is to measure the temperature of a hot-spot. There are
three such positions on the EXB30. The hottest is dependent on the
input line voltage, output load and even the ambient temperature.
In general they will be within 10˚C of each other. These hot spots
are shown in Figure 13 for the low ouput voltage models and are the
main primary switch, two synchronous rectifiers (the thermocouples
should be mounted as closely as possible to the tabs of the
devices) and the bias supply controller. For the 12V model, three
hot spot locations are shown in Figure 13B (i.e. main switch, diode
rectifier and bias supply controller)
Figure 13a - Hot Spot Locations on EXB30 2V,
2.5V, 3.3V and 5V Models
Figure 13b - Hot Spot Locations on EXB30 12V Model
In order to maintain the Artesyn derating criteria and comply with
safety standards the temperatures of the hotspots should never rise
above 120˚C.
Remote On/Off Control
The remote on/off control feature allow the user to switch the
converter on and off electronically when the appropriate signal is
applied to the remote pin. This is a primary referenced function
which allows the converter to be put in a low dissipating sleep
mode.
The EXB30 models are available in a positive logic remote on/off
configuration. The control pin is held high through an internal
resistor.
Positive Logic
This means that for the active high model, no connection is needed
to the control pin for the module to be enabled. However, the
control pin needs to be driven low and kept low to put the module
into sleep mode.
Specification for the Remote On/Off
See signal electrical interface on the EXB30 data sheet.
Isolated Closure Remote On/Off
An isolated closure is a closure with both high and low impedance
states that sinks current, but does not source current. For on/off
control the closure is between the on/off pin and Vi(-), this can be a
device such as a mechanical switch, open collector transistor or
opto-isolator.
Figure 14 - Isolated Closure using a Transistor
Note in the data sheet, the ‘acceptable high level leakage current’.
The maximum acceptable leakage current is 50µA. The isolation
device should have a leakage current less than this value or the
module may go into a low power dissipation mode (remote off).
VI(+)
On/Off
VOn/Off
RBE
RB
Remote
On/Off
+
-
EXB30
VI(-)
Ion/off
-40˚C
0%
20%
40%
60%
80%
100%
Ambient Temperature
Rated Output Current
-20˚C0˚20˚C40˚C60˚C80˚C 100˚C
100˚C
110˚C
If the remote sense feature is not required, it is necessary to
short the sense terminals to the respective power terminals as
shown in Figure 17.
Figure 17 - Circuit Configuration when Remote
Sense is not required
Output Voltage Adjustment
The output can be externally trimmed by -20% to +10% for low
voltage models or -40% to +10% for the 12V model by connecting an
external resistor between the TRIM pin and either the Vsense + or
Vsense - pins.
With an external resistor between TRIM and Vsense-, (RTRIM_DOWN)
the output voltage setpoint decreases (See Figure 18). Conversely,
connecting an external resistor between TRIM and Vsense+
(RTRIM_UP), the output voltage setpoint increases (See Figure 19).
Figure 18 - Circuit Configuration to Decrease Output Voltage
Figure 19 - Circuit Configuration to Increase Output Voltage
The equations used to determine the value of the external resistor
(specified in kΩ) required to obtain the desired output voltage are
shown below (∆= % change expressed in decimals):
I - ∆
RTRIM_DOWN =[] 10kΩfor all models
∆
Vo(nom) I + ∆
RTRIM_UP =[-1 ] [ ]10kΩ
Vref ∆
Where Vo (nom) is the default output voltage of the module.
Level Controlled Remote On/Off
Units can also be controlled by applying a voltage to the remote
on/off pin. The figure below shows a TTL output control.
Figure 15 - Level Control using TTL Output
As per the data sheet the TTL must be capable of sinking the
maximum low level input current of 100µA.
Remote Sense Compensation
The remote sense compensation feature minimises the effects of
resistance in the distribution system and facilitates accurate voltage
regulation at the load terminals or other selected point. The remote
sense lines will carry very little current and hence do not require a
large cross-sectional area. However, if the sense lines are routed on
a PCB, they should be located close to a ground plane in order to
minimise any noise coupled onto the lines that might impair control
loop stability. In a discrete wiring situation, the use of a twisted pair
or any other technique to reduce noise susceptability is
recommended. A small 100nF ceramic capacitor can be connected
at the point of load to decouple any noise on the sense wires as
outlined in Figure 16.
Figure 16 - Circuit Configuration for Remote Sense Operation
The power module will typically compensate for a maximum drop of
10% of the nominal output voltage. In other words, the voltage
difference between the power terminals and the sense terminals
must not exceed the maximum output sense range specified in the
data sheet, i.e.
[Vo+ - Vo-] - [Vsense+ - Vsense-] < 10% Vo(nom)
However, if trim up and remote sense are used in combination, the
overvoltage setpoint might be reached and the output voltage at the
power terminals will be clamped at this level.
EXB30 SERIES |
Application Note 108
PAGE 9
Vin
Vi+
Vi-
Vo+
Vsense+
Contact and Distribution
Losses
Io
Load
Vsense-
Vo-
+ Sense
Trim
- Sense
Rtrim_down
+ Sense
Trim
- Sense
Rtrim_up
Vin
Vi+
Vi-
Vo+
Vsense+
Contact and Distribution
Losses
Io
Load
Vsense-
Vo-
100n
VI(+)
On/Off
VOn/Off
Ion/off
Remote
On/Off
TTL Gate
+
-VI(-)
EXB30
Vref = 2.5V, 5V and 12V models
Vref = 1.225V for 2.0V, 2.5V and 3.3V models
RTRIM_UP The resistor r equired to achieve the desir ed trimmed
up output voltage
RTRIM_DOWN resistor required to achieve the desired trimmed
down output voltage
Example:
To trim up the 5V model by 5% to 5.25V the requir ed external resistor
is:
5 1 + 0.05
RTRIM_UP =[-1 ] [ ]10kΩ= 210kΩ
2.5 0.05
To trim down by 10% the required resistor is:
1 - 0.1
RTRIM_DOWN =[]10kΩ= 90kΩ
0.1
Note that the resistor required to trim down is independent of output
voltage, whereas the resistor required to trim up is largely dependent
on output voltage.
When the output voltage is trimmed up a certain percentage, the
output current must be derated by the same amount so that the
maximum output power is not exceeded.
Output Capacitance
The EXB30 series of DC/DC converters has been designed to be
stable operation without the need for external capacitors at the input
or output terminals when powered from a low impedance source.
However, when powering loads with large dynamic current
requirements, improved voltage regulation can be obtained by
inserting decoupling capacitors as close as possible to the load. Low
ESR ceramic capacitors will handle high frequency current
components while tantalum capacitors can be used to supply the
lower frequency dynamic current variations. Note that the absolute
maximum value of output capacitance is 10,000µF for the 2V, 2.5V,
3.3V and 5V models and 2,000µF for the 12V model. For larger
capacitance values than this please contact the local Artesyn
Technologies representative.
Reflected Input Current Measurement:
The circuit shown in Figure 20 has been used to measure the
reflected input current. Capacitor Cin is used to offset any
impedance that may occur between the converter and the battery.
This filter may also be connected on the input side of the EXB30 to
reduce the reflected input ripple current.
EXB30 SERIES |
Application Note 108
PAGE 10
http://www.artesyn.com
Figure 20 - Reflected Ripple Current Measurement Set-up
with Recommended Filter for Ripple Current Reduction
Parallel Operation
Because of the absence of an active current sharing feature, parallel
operation of multiple EXB30 converters is generally not
recommended. If unavoidable, Oring-diodes have to 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.
+Vin
-Vin
Cin
220µF Electrolytic
ESR<0.12Ω
@100kHz
12µH
To Input Curent
Measurement device
EXB30
EXB30 SERIES |
Application Note 108
PAGE 11
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 21 - Output Noise and Ripple Set-up
Output Noise and Ripple Measurement
The above circuit has been used for noise measurement on EXB30
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.
PAGE 12
http://www.artesyn.com
AN_EXB30_20001020.PDF
Application Note © Artesyn Technologies
®
2000
The information and specifications contained in this application note are believed to be correct at time of publication. However, Artesyn Technologies accepts no responsibility for consequences arising
from printing errors or inaccuracies. Specifications are subject to change without notice. No rights under any patent accompany the sale of any such product(s) or information contained herein.
UV
GND
-48V
R4 R7
8
1
7
C4
100µ
100V
C3
0.1µ
100V
C1
33nF R2
10R
R3
10k C2
3n3
R1
0.02R Q1
IRF530
C5
100µ
16V
654
3
2
R5
R6
VDD
OV
VEE SENSE GATE DRAIN
PWRGD
Remote ON/OFF
Vin+
Vin-
Vo+
Vo-
LT1640H
EXB30-48SXXX Vsense+
Vsense-
Figure 22 - LT1640H Hot Swap Controller Interface with EXB30-48SXXX
Compatibility with LT®1640L/LT1640H Hot Swap Controller
The LT®1640L/LT1640H is an 8-pin, negative voltage Hot Swap®
controller that allows a board to be safely inserted and removed from
a live backplane. The EXB30 modules are compatible with LT1640H
part.
It provides the following features:
1 Inrush current is limited to a programmable value by controlling
the gate voltage of an external N-channel pass transistor.
2 The pass transistor is turned-off if the input voltage is less than the
programmable undervoltage threshold or greater than the
overvoltage threshold. A programmable electronic circuit breaker
protects the system against shorts.
3 The LT1640H is designed for modules with a high enable input.
The PWRGD signal can be used to directly enable a power
module.
The UV (pin 3) and OV (pin 2) pins can be used to detect undervoltage
and overvoltage conditions at the power supply unit. The EXB30 has
already got undervoltage and overvoltage pr otection in-built to ensure
that the unit does not draw power from the power sour ce for voltages
less than 32V and greater than 78V. Resistors R4, R5 and R6
determine the undervoltage and overvoltage levels. Users should
refer to data sheet of the LT1640 for formulae to set the required
UVLO and OVLO trip levels.
The PWRGD output can be used to directly enable the EXB30. This
is an open collector output with minimum output impedance of 2kΩ.
The pull-up resistor (R7) r equired to ensur e that the Remote on/of f pin
voltage is greater than 2V at an input voltage of 30V is 33kΩ. This
results in a maximum power dissipation in R7 at Vinmax (75V) to be
approximately 0.2W.
Typically the PWRGD signal is not required for inrush current control
and thus, this 0.2W maximum power dissipation can be avoided if the
user controls the Remote on/off pin voltage level by other means.
EXB30 SERIES |
Application Note 108