
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
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