FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Applications
RF Power Amplifiers
Wireless communications
Benefits
High efficiency
Low cost
Integrated metal baseplate design
Higher power output at elevated temperatures and
low airflow
Features
RoHS lead-free solder and lead-solder-exempted
products are available
28V regulated output at 700W
Efficiency up to 92%
Fixed-frequency operation
Start-up into pre-biased load
No minimum load required
Fully protected: UVLO, OCP, OTP, and OVP
Current share
Output Good signal
Auxiliary Output of 7 to 9V at up to 20 mA
Output voltage trim range: +15%/40% with
industry-standard trim equations
Remote differential output voltage sense
Isolated two-pin ON/OFF
On-board input differential LC-filter
Industry-standard fullbrick size and pinout
Low height of 0.50” (12.7mm)
Wide operating temperature range from -40 to 100°C
High reliability: MTBF = TBD million hours
UL60950 recognized in US and Canada and
DEMKO certified per IEC/EN60950 (pending)
All materials meet UL94, V-0 flammability rating
Description
The new high performance 700W FBA48T25280 DC-DC converter provides a high efficiency single 28V output in
the fullbrick package. Specifically designed for operation in wireless systems that have limited airflow and
increased ambient temperatures, the FBA48T25280 converter utilizes the same pinout and functionality as the
industry-standard power amplifier bricks.
Operating from a 36-75V input, the FBA48T25280 converter provides a full regulated 28V output voltage that can
be trimmed from –40% to +15% of the nominal output voltage, thus providing outstanding design flexibility. The
open frame module is constructed with a dual board approach using the metal baseplate and discrete magnetics.
The standard feature set includes remote ON/OFF, differential output voltage sensing, input undervoltage lockout,
overtemperature, output overvoltage and overcurrent protections, current sharing, auxiliary voltage output, and the
Output Good signal.
With standard pinout and trim equations, the FBA48T25280 converter is a perfect solution for existing and new
designs. Inclusion of this converter in a design can result in significant power and cost savings. The designer can
expect reliability improvement over other available converters because of the FBA48T25280’s optimized thermal
efficiency.
ZD-02015 Rev 1.3 www.power-one.com Page 1 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Electrical Specifications
Conditions: TA = 25 ºC, Vin = 48 VDC, Cin=2x220µF, Cout=220µF unless otherwise specified.
Parameter Notes Min Typ Max Units
Absolute Maximum Ratings
Input Voltage Continuous 0 75 VDC
Input Voltage Transient 100 ms 100 VDC
Operating Ambient Temperature Limited by baseplate temperature -40 85 °C
Operating Baseplate Temperature -40 100 °C
Storage Temperature -55 125 °C
Isolation Characteristics
Input to Output Isolation 1500 VDC
Isolation Capacitance 2600 pF
Isolation Resistance 10 M
Input to Baseplate Isolation 1500 VDC
Output to Baseplate Isolation 500 VDC
Feature Characteristics
Switching Frequency 300 kHz
Output Voltage Trim Range1Industry-standard equations -40 +15 %
Remote Sense Compensation1Percent of VOUT(NOM) +10 %
Output Overvoltage Protection Latching 120 128 135 %
Overtemperature Protection (baseplate) Non-latching 120 125 130 °C
Overtemperature Protection Hysteresis 10 °C
ON/OFF Control Controlled by current between ON/OFF+ and ON/OFF- pins
Converter OFF (current is low) -10 0.1 mADC
Converter ON (current is high) 1 5 mADC
Auxiliary Output Voltage 7 9 VDC
Auxiliary Output Current No protected from overcurrent 20 mADC
Output Good Signal (open collector) Output is in regulation – Low, Output is out of regulation - High
Output Good Current Sink 5 mADC
Output Good External Pull-up Voltage 35 VDC
Current Share Accuracy Two units connected in parallel ±10%
Parallel Pin Voltage 156 mV/A
Additional Notes:
1 Vout can be increased up to 10% via the sense leads or 15% via the trim function. However, the total output voltage trim from all sources
should not exceed 15% of VOUT(NOM).
ZD-02015 Rev 1.3 www.power-one.com Page 2 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Electrical Specifications (continued)
Conditions: TA = 25 ºC, Vin = 48 VDC, Cin=2x220µF, Cout=220µF unless otherwise specified..
Parameter Notes Min Typ Max Units
In
p
ut Characteristics
Operating Input Voltage Range 36 48 75 VDC
Input Undervoltage Lockout
Turn-on Threshold 33 36 VDC
Turn-off Threshold 31.5 34.5 VDC
UVLO Hysteresis 1.5 VDC
Maximum Input Current Full Load at 36VDC In
25 ADC
Input Standby Current Vin = 48V, converter disabled 25 mA
Input No Load Current (0A load on the output) Vin = 48V, converter enabled 30 mA
Input Reflected-Ripple Current, icVin = 48V, 25 MHz bandwidth
(Figure 13)
30
7
mAPK-PK
mAPK-PK
Input Ripple Current, isVin = 48V, 25 MHz bandwidth
(Figure 13)
2000
500
mAPK-PK
mAPK-PK
Input Voltage Ripple Rejection 120 Hz TBD dB
Out
p
ut Characteristics
External Load Capacitance Plus full load (resistive) 220 10,000 µF
Turn-On Time from Vin Time from UVLO to Vo=90%VOUT(NOM) 30 ms
Turn-On Time from ON/OFF Time from Enable to Vo=90%VOUT(NOM) 15 ms
Output Current Range 0 25 ADC
Current Limit Inception Non-latching 27.5 30 33 ADC
Peak Short-Circuit Current Non-latching, Short = 10 m
65 A
RMS Short-Circuit Current Non-latching
35 Arms
Output Voltage Set Point (no load) 27.72 28.28 VDC
Output Regulation
Over Line
±28 ±56 mV
Over Load ±28 ±56 mV
Over Temperature 200 DPPM
Output Voltage Range Over line, load and temperature 27.25 28.50 VDC
Output Ripple and Noise – 25 MHz bandwidth Full load + 10µF tantalum + 1µF ceramic
+220uF electrolytic 190 280 mVPK-PK
D
y
namic Res
p
onse
Load Change 50%-75%-50% of Iout Max,
di/dt = 0.1 A/µs
450 mV
di/dt = 1A/µs Co =10,000µF
450 mV
Settling Time to 1% of Vout
500 µs
Mechanical
Weight TBD g
Operating Humidity RH (non-condensing) 95 %
Storage Humidity RH (non-condensing) 95 %
Vibration (Sinusoidal) GR-63-CORE, Section 5.4.2
Shock Half Sinewave, 3-axis 50 g
Reliability
MTBF Telcordia SR-332, Method I Case 1
50% electrical stress, 40°C ambient TBD MHrs
ZD-02015 Rev 1.3 www.power-one.com Page 3 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Operations
Input and Output Impedance
These power converters have been designed to be
stable with a minimum external output capacitor of
220µF when used in low inductance input and output
circuits. If the ambient temperature is lower than
-20°C, then use 4 x 220uF to reduce ESR. Nichicon
UPW1H221MPD or equivalent is recommended.
In many applications, the inductance associated with
the distribution from the power source to the input of
the converter can affect the stability of the converter.
It is recommended that 2 x 220µF with a voltage
rating of 100VDC be used on the input of the
FBA48T25280.
In applications where the user has to use decoupling
capacitance at the load, the power converter will
exhibit stable operation with the external load
capacitance up to 10,000 µF.
ON/OFF Control (Pins 1 and 2)
The ON/OFF pins are used to turn the power
converter on or off remotely via a system signal. The
on/off control is a current driven control. It is isolated
from both the primary and the secondary by
1500VDC. The ON/OFF control turns the converter
on when 1 to 5 mA of current flows from the
ON/OFF+ pin to the ON/OFF- pin. The converter is
off when no current or a small reverse current flows
between the pins. Maximum reverse voltage shall
not exceed 6VDC.
The ON/OFF control current can be generated from
the primary or from the secondary as shown in the
application schematics in Figure 1 and Figure 2.
Vin +
Vin -
On/Off -
On/Off +
Figure 1. ON/OFF Control Using Vin
Figure 2. ON/OFF Control Using Auxiliary Voltage
Remote Sense (Pins 16 and 17)
The remote sense feature of the converter
compensates for voltage drops occurring between
the output pins of the converter and the load. The
SENSE(-) (Pin 16) and SENSE(+) (Pin 17) pins
should be connected at the load or at the point
where regulation is required.
Figure 3. Remote sense circuit configuration.
CAUTION
If remote sensing is not utilized, the SENSE(-) pin must be
connected to the Vout(-) pin, and the SENSE(+) pin must be
connected to the Vout(+) pin to ensure the converter will
regulate at the specified output voltage. If these connections
are not made, the converter will deliver an output voltage that
is higher than the specified data sheet value.
Because the sense leads carry minimal current,
large traces on the end-user board are not required.
However, sense traces should be run side by side
and located close to a ground plane to minimize
system noise and ensure optimum performance.
The converter’s output overvoltage protection (OVP)
senses the voltage across VOUT+ and VOUT-, and
not across the sense lines, so the resistance (and
resulting voltage drop) between the output pins of
the converter and the load should be minimized to
prevent unwanted triggering of the OVP.
When utilizing the remote sense feature, care must
be taken not to exceed the maximum allowable
output power capability of the converter, which is
Rw
equal to the product of the nominal output voltage
Rw
Rload
Vin
Vin (+)
Vin (-)
VOUT+
VOUT-
TRIM
SENSE (+)
SENSE (-)
FBA48T25280
ZD-02015 Rev 1.3 www.power-one.com Page 4 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
and the allowable output current for the given
conditions.
When using remote sense, the output voltage at the
Output Voltage Adjust /TRIM (Pin 15)
5% or down
ming is not
he output voltage, refer to Figure 4. A
converter can be increased by as much as 10%
above the nominal rating in order to maintain the
required voltage across the load. Therefore, the
designer must, if necessary, decrease the maximum
current (originally obtained from the derating curves)
by the same percentage to ensure the converter’s
actual output power remains at or below the
maximum allowable output power.
The output voltage can be adjusted up 1
40%, relative to the rated output voltage by the
addition of an externally connected resistor. Trim up
to 15% is guaranteed only at Vin 40V.
The TRIM pin should be left open if trim
being used.
To increase t
trim resistor, RT-INCR, should be connected between
the TRIM pin and SENSE+ pin, with a value of:
2
1.225
22.51)V(100
RNOMO
INCRT
+
=
,[k]
where,
Required value of trim-up resistor k]
=INCRTR
=NOMOVNominal value of output voltage [V]
100X
V
)V(V
NOM- O
NOM-OREQ-O
= [%]
Desired (trimmed) output voltage [V].
When trim ceed
=REQOV
ming up, care must be taken not to ex
the converter‘s maximum allowable output power.
See the previous section for a complete discussion
of this requirement.
Figure 4. Configuration for increasing output voltage.
To decrease the output voltage (Figure 5), a trim
resistor RT-DECR should be connected between the
TRIM pin and the SENSE- pin, with a value of:
2
||
100
RDECRT =,[k]
where,
=DECRTRRequired value of trim-down resistor [k]
and
is defined above.
Figure 5. Configuration for decreasing output voltage.
Trimming/sensing beyond 115% of the rated output
voltage is not an acceptable design practice, as this
condition could cause unwanted triggering of the
output overvoltage protection (OVP) circuit. The
designer should ensure that the difference between
the voltages across the converter’s output pins and its
sense pins does not exceed 15% of VOUT(NOM), or:
X NOM-O SENSESENSEOUTOUT 15%V)](V)([V)](V)([V
+
+
[V]
This equation is applicable for any condition of output
sensing and/or output trim.
Parallel Applications
The FBA48T25280 features the active current share
circuit to ensure that the two converters connected in
parallel will share current within ±10% of the total
output current.
Rload
Vin
Vin (+)
Vin (-)
VOUT+
VOUT-
TRIM
SENSE (+)
SENSE (-)
RT-INCR
FBA48T25280
Rload
Vin
Vin (+)
Vin (-)
VOUT+
VOUT-
TRIM
SENSE (+)
SENSE (-)
RT-DECR
FBA48T25280
ZD-02015 Rev 1.3 www.power-one.com Page 5 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Auxiliary Voltage Output (Pin 12)
The FBA48T25280 has the auxiliary voltage output
voltage connected to pin 12. The voltage on this pin
is not precisely regulated and will vary from 7V to 9V
depending on line and load conditions. This output
is not internally protected and shorting this pin to
ground or to any of the other converter terminals
may cause permanent damage to the converter.
Output Voltage Good signal (IOG) (Pin13)
The signal on pin 13 is active low (open collector).
Whenever the output voltage is out of regulation the
pin is in the high impedance state. The IOG pin can
sink the maximum of 5mADC and it can be externally
pulled up to the maximum of 35VDC.
Protection Features
Input Undervoltage Lockout
Input undervoltage lockout is standard with this
converter. The converter will shut down when the
input voltage drops below a pre-determined voltage.
The input voltage must be typically 34 V for the
converter to turn on. Once the converter has been
turned on, it will shut off when the input voltage
drops typically below 32 V. This feature is beneficial
in preventing deep discharging of batteries used in
telecom applications.
Output Overcurrent Protection (OCP)
The converter is protected against overcurrent or
short circuit conditions. Upon sensing an overcurrent
condition, the converter will switch to constant
current operation and thereby begin to reduce its
output voltage.
When the output voltage drops below 10% of the
nominal value of output voltage, the converter will
shut down.
Once the converter has shut down, it will attempt to
restart nominally every 20 ms with a typical 20% duty
cycle. The attempted restart will continue indefinitely
until the overload or short circuit condition is
removed or the output voltage rises above 90% of its
nominal value.
Once the output current is brought back into its
specified range, the converter automatically exits the
hiccup mode and continues normal operation.
Output Overvoltage Protection (OVP)
The converter will shut down if the output voltage
across VOUT+ and VOUT- exceeds the threshold of
the OVP circuitry. The OVP circuitry contains its own
reference, independent of the output voltage
regulation loop. Once the converter has shut down it
will latch off. The latch can be reset by toggling the
ON/OFF inputs or by recycling the input voltage..
Overtemperature Protection (OTP)
The converter will shut down under an
overtemperature condition to protect itself from
overheating caused by operation outside the thermal
derating curves, or operation in abnormal conditions
such as system fan failure. Ince the converter has
shut down, it will automatically restart after it has
cooled to a safe operating temperature.
Safety Requirements
The converters meet North American and
International safety regulatory requirements per
UL60950 and EN60950. Basic Insulation is provided
between input and output.
The converters have no internal fuse. If required, the
external fuse needs to be provided to protect the
converter from catastrophic failure. Refer to the
“Input Fuse Selection for DC/DC converters”
application note on www.power-one-com for proper
selection of the input fuse. Both input traces and the
chassis ground trace (if applicable) must be capable
of conducting a current of 1.5 times the value of the
fuse without opening. The fuse must not be placed
in the grounded input line.
Abnormal and component failure tests were
conducted with the input protected by a 30A fuse. If
a fuse rated greater than 30A is used, additional
testing may be required. To protect a group of
converters with a single fuse, the rating can be
increased from the recommended value above.
Electromagnetic Compatibility (EMC)
EMC requirements must be met at the end-product
system level, as no specific standards dedicated to
EMC characteristics of board mounted component
dc-dc converters exist. However, Power-One tests its
converters to several system level standards,
primary of which is the more stringent EN55022,
Information technology equipment - Radio
disturbance characteristics-Limits and methods of
measurement.
An effective internal LC differential filter significantly
reduces input reflected ripple current, and improves
EMC.
With the addition of a simple external filter, the
FBA48T25280 converter passes the requirements of
Class A conducted emissions per EN55022 and FCC
ZD-02015 Rev 1.3 www.power-one.com Page 6 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
requirements. Refer to Figure 6 for the
recommended configuration of the input filter.
Figure 6. Input Filter Configuration Required to Meet CISPR 22
Class A for Conducted Emissions.
Startup Information
Scenario #1: Initial Startup From Bulk Supply
ON/OFF function enabled, converter started via application
of VIN. See Figure E.
Time Comments
t0ON/OFF pin is ON; system front-end power is
toggled on, VIN to converter begins to rise.
t1VIN crosses undervoltage Lockout protection
circuit threshold; converter enabled.
t2Converter begins to respond to turn-on
command (converter turn-on delay).
t3Converter VOUT reaches 90% of nominal value.
For this example, the total converter startup time (t3- t1) is
typically 30 ms.
Scenario #2: Initial Startup Using ON/OFF Pin
With VIN previously powered, converter started via
ON/OFF pin. See Figure F.
Time Comments
t0VINPUT at nominal value.
t1Arbitrary time when ON/OFF pin is enabled
(converter enabled).
t2End of converter turn-on delay.
t3Converter VOUT reaches 90% of nominal value.
For this example, the total converter startup time (t3- t1) is
typically 15 ms.
Figure 7. Startup scenario #1.
Figure 8. Startup scenario #2.
ON/OFF
STATE
VOUT
t0t
1t 2t
3
OFF
ON
VIN
t
VIN
ON/OFF
STATE
VOUT
t
t0t1t2t3
ON
OFF
ZD-02015 Rev 1.3 www.power-one.com Page 7 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Characterization
General Information
The converter has been characterized for many
operational aspects, to include thermal derating
(maximum load current as a function of baseplate
temperature), efficiency, startup and shutdown
parameters, output ripple and noise, transient
response to load step-change, overload, and short
circuit.
The following pages contain specific plots or
waveforms associated with the converter. Additional
comments for specific data are provided below.
Test Conditions
All thermal data presented was taken with the
converter mounted to a 6”x12”x1” finned heatsink.
The FBA is designed to operate in an enclosed
environment with the dissipated power being
extracted though the baseplate into the heatsink.
Thermocouples were used to ensure that the internal
components were operating with in their SOA with
the baseplate at 100°C. Refer to Figure 9 for the
optimum thermocouple location.
Thermal Derating
For each set of conditions, the maximum load
current was defined as the lowest of:
(i) The output current at which the base plate
temperature does not exceed a maximum specified
temperature of 100°C as indicated by thermocouple
measure, or
(ii) The nominal rating of the converter.
Temperature at the thermocouple location shown in
Figure 9 should not exceed 100°C in order to operate
inside the derating curves.
Figure 9. Location of the thermocouple for thermal testing.
The derating curve showing available output power as
a function of the baseplate temperature is shown in
Figure 12.
Efficiency
Figure 10 shows the efficiency vs. load current plot for
ambient temperature of 25°C and input voltages of
36V, 48V, 60V, and 75 V.
Power Dissipation
Figure 11 shows the power dissipation vs. load current
plot for Ta = 25°C and input voltages of 36V, 48V,
60V, and 75V.
Vin
+
Vin
-
On/Of
f
-
On/Of
f
+
+Vout
-Vout
-Vout
-Vout
+Vout
+Vout
2.30"
1.2"
ZD-02015 Rev 1.3 www.power-one.com Page 8 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Characterization Data
Efficiency Curves
86%
87%
88%
89%
90%
91%
92%
51015202
Load Current, A
Efficiency
5
36V
48V
60V
75V
.
Figure 12. Available Power Vs. Baseplate Temperature
Test Setup
Figure 10. Efficiency vs. load current and input voltage for
FBA48T25280 converter at Ta=25°C.
15
25
35
45
55
65
75
85
5 1015202
Load Current, A
Power Dissipation, W
5
36V
48V
60V
75V
Figure 13. Test setup for measuring input reflected ripple
currents, ic and is.
Figure 11. Power dissipation vs. load current and input
voltage for FBA48T25280 converter at Ta = 25°C.
ZD-02015 Rev 1.3 www.power-one.com Page 9 of 10
FBA48T25280 DC-DC Converter
36-75 VDC Input; 28VDC @ 25A Output
Preliminary Data Sheet
Physical Information
Pad/Pin # Function
1 ON/OFF+
2 ON/OFF-
3 +VIN
4 -VIN
5 -VOUT
6 -VOUT
7 -VOUT
8 +VOUT
9 +VOUT
10 +VOUT
11 Not used
12 AUX
13 IOG
14 Parallel
15 TRIM
16 -SENSE
17 +SENSE
FBA48T Platform Notes
All dimensions are in inches [mm]
Pins 1-2 and 12-17 are Ø 0.040”
[1.02] without a shoulder
Pins 3-10 are Ø 0.080” [2.04]
without a shoulder
Pin Material: Brass Alloy 360
Pin Finish: Tin over Nickel
Tolerances: [Unless otherwise indicated]
x.xxx in. +/- .010 [x.xx mm +/- 0.25]
x.xx in. +/- .020 [x.x mm +/- 0.5]
Converter Part Numbering/Ordering Information
Product
Series
Input
Voltage
Mounting
Scheme
Rated
Current
Output
Voltage ON/OF
F Logic
Maximum
Height [HT]
Pin Length
[PL] Special Features RoHS
FBA 48 T 25 280 - P C A P G
FullBrick
Format 36-75 V
T
Through-
hole
25
25ADC
280
28V P
Positive C 0.52”
Through
hole
A 0.188”
B 0.145”
P Parallellable
Q Parallellable
with M3 threaded
standoffs
N Not
parallellable
M Not
parallellable with
M3 threaded
standoffs
No Suffix
RoHS
lead-solder-
exemption
compliant
G RoHS
compliant for
all six
substances
The example above describes P/N FBA48T25280-PCAPG: 36-75 V input, through-hole, 25A @ 28V output, positive ON/OFF logic,
maximum height of 0.52”, 0.188” pins, parallelable with non-threaded standoffs, and RoHS compliant for all 6 substances.
Notes:
1. NUCLEAR AND MEDICAL APPLICATIONS - Power-One products are not designed, intended for use in, or authorized for use as critical
components in life support systems, equipment used in hazardous environments, or nuclear control systems without the express written
consent of the respective divisional president of Power-One, Inc.
2. TECHNICAL REVISIONS - The appearance of products, including safety agency certifications pictured on labels, may change depending
on the date manufactured. Specifications are subject to change without notice.
ZD-02015 Rev 1.3 www.power-one.com Page 10 of 10