UHP28_2_12A Datasheet, PDF (4/9 Pages) Murata Manufacturing Co., Ltd. – Isolated, 12 Amp Half Brick, 48VIN/28.2VOUT DC/DC Converters

UHP-28.2/12-D48
Isolated, 12 Amp Half Brick, 48VIN/28.2VOUT DC/DC Converters
Performance/Functional Specification Notes:
(3) Note that Maximum Power Derating curves indicate an average current at nominal input voltage.
At higher temperatures and/or lower airflow, the DC/DC converter will tolerate brief full current
outputs if the total RMS current over time does not exceed the Derating curve.
(4) Mean Time Before Failure is calculated using the Telcordia (Belcore) SR-332 Method 1,
Case 3, ground fixed conditions, TCASE = +40°C, full output load, natural air convection.
(5) The On/Off Control may be driven with external logic or by applying appropriate external voltages
which are referenced to Input Common. The On/Off Control Input should use either an open col-
lector/open drain transistor or logic gate which does not exceed +12V.
(6) Short circuit shutdown begins when the output voltage degrades approximately 2% from the
selected setting. Remove overload for recovery.
(7) Input overvoltage shutdown is explicitly not included to improve system reliability in datacom and
telecom applications. These requirements attempt continued operation despite significant input
overvoltage.
(8) Output noise may be further reduced by adding an external filter. See I/O Filtering and Noise
Reduction. Use only as much external output filtering as needed and no more. Larger caps
(especially low-ESR ceramic types) may degrade dynamic performance or cause possible failed
starts. Thoroughly test your application with all components installed.
(9) Models are fully operational and meet published specifications, including “cold start” at –40°C.
(10) Regulation specifications describe the deviation as the line input voltage or output load current is
varied from a nominal midpoint value to either extreme.
(11) If the input voltage is reversed, a normally back-biased bulk substrate diode will become forward
biased and draw current. An external fuse is recommended to avoid damage from reverse input
current.
(12) Do not exceed maximum power specifications when adjusting the output trim.
(13) Note that the converter may operate derated up to +110°C with the baseplate installed. However,
thermal self-protection occurs near +115°C and there is a thermal gradient from the hotspot to
the baseplate. Therefore, +110°C is recommended to avoid thermal shutdown.
(14) If the output exceeds the Overvoltage specification, the output will shut down in latching mode.
To restore normal operation, either power down the unit or cycle the On/Off control.
(15) Acoustic output is measured by subjecting the converter to both 0-100-0% and 50-100-50%
step loads at load pulse frequencies of 100Hz, 300Hz and 1kHz.
TECHNICAL NOTES
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. Fuses should also be
used if the possibility of sustained, non-current-limited, input-voltage polarity
reversals exists. For DATEL UHP Series DC/DC Converters, we recommend the
use of slow-blow type fuses, installed in the ungrounded input supply line,
with values no greater than the following.
Output
Fuse Value
28 VOUT
18 Amp
All relevant national and international safety standards and regulations must
be observed by the installer. For system safety agency approvals, the convert-
ers must be installed in compliance with the requirements of the end-use
safety standard, i.e. IEC/EN/UL60950.
Input Undervoltage Shutdown and Start-Up Threshold
Under normal start-up conditions, devices will not begin to regulate properly
until the ramping-up input voltage exceeds the Start-Up Threshold Voltage.
Once operating, devices will not turn off until the input voltage drops below
the Undervoltage Shutdown limit. Subsequent re-start will not occur until the
input is brought back up to the Start-Up Threshold. This built in hysteresis pre-
vents any unstable on/off situations from occurring at a single input voltage.
Start-Up Time
The VIN to VOUT Start-Up Time is the interval of time between the point at which
the ramping input voltage crosses the Start-Up Threshold and the fully loaded
output voltage enters and remains within 90% of VOUT . Actual measured times
will vary with input source impedance, external input capacitance, and the
slew rate and final value of the input voltage as it appears at the converter.
The UHP Series implements a soft start circuit that limits the duty cycle of its
PWM controller at power up, thereby limiting the input inrush current.
The On/Off Control to VOUT start-up time assumes the converter has its
nominal input voltage applied but is turned off via the On/Off Control pin. The
specification defines the interval between the point at which the converter is
turned on (released) and the fully loaded output voltage enters and remains
within its specified accuracy band.
Similar to the VIN to VOUT start-up, the On/Off Control to VOUT start-up time is
also governed by the internal soft start circuitry and external load capacitance.
The difference in start up time from VIN to VOUT and from On/Off Control to VOUT
is therefore insignificant.
Input Overvoltage Shutdown
The UHP Series does not feature input overvoltage shutdown. The converters
do withstand and fully operate during input transients to 100V for 100msec
without interruption; consequently, this function has been disabled.
Input Source Impedance
The input of UHP converters must be driven from a low ac-impedance source.
The DC/DC's performance and stability can be compromised by the use of
highly inductive source impedances. The input circuit shown in Figure 2 is a
practical solution that can be used to minimize the effects of inductance in the
input traces. For optimum performance, components should be mounted as
close as possible to the DC/DC converter.
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