
MCD10157 Rev. 1.0, 12-May-10
www.power-one.com
Page 5 of 13
SQE48T20120 DC-DC Converter
36-75 VDC Input; 12 VDC @ 20 A Output
Preliminary Data Sheet
Protection Features
Input Undervoltage Lockout (UVLO)
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 35V for the
converter to turn on. Once the converter has been
turned on, it will shut off when the input voltage
drops typically below 33V. 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 shut down.
Once this occurs, it will enter hiccup mode and
attempt to restart approximately every 300 ms with
an approximate duty cycle of 5%. The attempted
restart will continue indefinitely until the overload or
short circuit condition is removed.
Once the output current is brought back into its
specified range, the converter automatically exits the
hiccup mode and resumes 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 attempt to restart every 300 ms until the OVP
condition is removed.
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. The converter will
automatically restart after it has cooled to a safe
operating temperature.
Safety Requirements
The
converters
are
safety
approved
to
UL/CSA60950-1,
EN60950-1, and IEC60950-1.
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 10A fuse. If
a fuse rated greater than 10A 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
SQE48T20120 converter will pass the requirements
of Class B conducted emissions per EN55022 and
FCC requirements. Refer to Figures 14 – 15 for
typical performance with external filter.