QM48T45 Family DC-DC Converter Data Sheet
36-75 VDC Input; 1.0-3.3 VDC @ 45 A Output
Protection Features
Input Undervoltage Lockout
Safety Requirements
Input undervoltage lockout is standard with this
converter. The converter will shut down when the
input voltage drops below a pre-determined voltage.
The converters meet North American and
International safety regulatory requirements per
UL60950 and EN60950. Basic Insulation is provided
between input and output.
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.
To comply with safety agencies’ requirements, an
input line fuse must be used external to the converter.
The Table below provides the recommended fuse
rating for use with this family of products.
Output Voltage
3.3 V
Fuse Rating
Output Overcurrent Protection (OCP)
10 A
7 A
5 A
3 A
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 output
voltage. When the output voltage drops below 60%
of its nominal value, the converter will shut down.
2.5 V
2.0-1.5 V
1.2-1.0 V
All QM converters are UL approved for a maximum
fuse rating of 15 Amps. To protect a group of modules
with a single fuse, the rating can be increased from
the recommended value above.
Once the converter has shut down, it will attempt to
restart nominally every 100 ms with a typical 1-2%
duty cycle. The attempted restart will continue
indefinitely until the overload or short circuit
conditions are removed or the output voltage rises
above 60% of its nominal value.
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
Once the output current is brought back into its
specified range, the converter automatically exits the
hiccup mode and continues normal operation.
technology
equipment
-
Radio
disturbance
Output Overvoltage Protection (OVP)
characteristics-Limits and methods of measurement.
The converter will shut down if the output voltage
across Vout(+) (Pin 8) and Vout(-) (Pin 4) 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 attempt to restart every 100 ms until the
OVP condition is removed.
An effective internal LC differential filter significantly
reduces input reflected ripple current, and improves
EMC.
With the addition of a simple external filter, all
versions of the QmaX™ Series of converters pass the
requirements of Class B conducted emissions per
EN55022 and FCC requirements. Please contact
Power-One Applications Engineering for details of this
testing.
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. After the converter has
cooled to a safe operating temperature, it will
automatically restart.
Fig. E: Location of the thermocouple for thermal testing.
MCD10073 Rev. 1.0
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