BEI15 Series
Isolated Wide Input Bipolar 15-Watt DC/DC Converters
MDC_BEI15W.A18 Page 14 of 15
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Minimum Output Loading Requirements
All models regulate within specifi cation and are stable under 10% minimum
load to full load conditions. Operation under no load might however slightly
increase output ripple and noise.
Thermal Shutdown
To protect against thermal overstress, these converters include thermal shut-
down circuitry. If environmental conditions cause the temperature of the DC/
DC’s to rise above the Operating Temperature Range up to the shutdown tem-
perature, an on-board electronic temperature sensor will power down the unit.
When the temperature decreases below the turn-on threshold, the converter
will automatically restart. There is a small amount of temperature hysteresis to
prevent rapid on/off cycling.
CAUTION: If you operate too close to the thermal limits, the converter may
shut down suddenly without warning. Be sure to thoroughly test your applica-
tion to avoid unplanned thermal shutdown.
Temperature Derating Curves
The graphs in this data sheet illustrate typical operation under a variety of
conditions. The Derating curves show the maximum continuous ambient air
temperature and decreasing maximum output current which is acceptable
under increasing forced airfl ow measured in Linear Feet per Minute (“LFM”).
Note that these are AVERAGE measurements. The converter will accept brief
increases in current or reduced airfl ow as long as the average is not exceeded.
Note that the temperatures are of the ambient airfl ow, not the converter
itself which is obviously running at higher temperature than the outside air.
Also note that very low fl ow rates (below about 25 LFM) are similar to “natural
convection”, that is, not using fan-forced airfl ow.
Murata Power Solutions makes Characterization measurements in a closed
cycle wind tunnel with calibrated airfl ow. We use both thermocouples and an
infrared camera system to observe thermal performance.
CAUTION: If you exceed these Derating guidelines, the converter may have
an unplanned Over Temperature shut down. Also, these graphs are all collected
near Sea Level altitude. Be sure to reduce the derating for higher altitude.
Output Current Limiting
Current limiting inception is defi ned as the point at which full power falls
below the rated tolerance. See the Performance/Functional Specifi cations.
Note particularly that the output current may briefl y rise above its rated value
in normal operation as long as the average output power is not exceeded. This
enhances reliability and continued operation of your application. If the output
current is too high, the converter will enter the short circuit condition.
Output Short Circuit Condition
When a converter is in current-limit mode, the output voltage will drop as the
output current demand increases. If the output voltage drops too low (approxi-
mately 98% of nominal output voltage for most models), the PWM controller
will shut down. Following a time-out period, the PWM will restart, causing
the output voltage to begin rising to its appropriate value. If the short-circuit
condition persists, another shutdown cycle will initiate. This rapid on/off cycling
is called “hiccup mode”. The hiccup cycling reduces the average output cur-
rent, thereby preventing excessive internal temperatures and/or component
damage.
Remote On/Off Control
The remote On/Off Control can be specifi ed with either logic logic type. Please
refer to the Connection Diagram on page 1 for On/Off connections.
Positive-logic models are enabled when the On/Off pin is left open or is
pulled high to +Vin with respect to –Vin. Therefore, the On/Off control can be
disconnected if the converter should always be on. Positive-logic devices are
disabled when the On/Off is grounded or brought to within a low voltage (see
Specifi cations) with respect to –Vin.
Negative-logic devices are on (enabled) when the On/Off pin is grounded or
brought to within a low voltage (see Specifi cations) with respect to –Vin. The
device is off (disabled) when the On/Off is pulled high (see Specifi cations) with
respect to –Vin.
Dynamic control of the On/Off function must sink the specifi ed signal current
when brought low and withstand the specifi ed voltage when brought high.
Be aware too that there is a fi nite time in milliseconds (see Specifi cations)
between the time of On/Off Control activation and stable, regulated output. This
time will vary slightly with output load type and current and input conditions.
Output Capacitive Load
These converters do not require external capacitance added to achieve rated
specifi cations. Users should only consider adding capacitance to reduce
switching noise and/or to handle spike current load steps. Install only enough
capacitance to achieve your noise and surge response objectives. Excess
external capacitance may cause regulation problems and possible oscillation
or instability.
The maximum rated output capacitance and ESR specifi cation is given for a
capacitor installed immediately adjacent to the converter.
Floating Outputs
Since these are isolated DC/DC converters, their outputs are "fl oating." Any
BEI15 model may be confi gured to produce an output of 10V, 24V or 30V (for
±5V, ±12V or ±15V models, respectively) by applying the load across the
+Output and –Output pins, with either output grounded. The Common pin
should be left open. Minimum 20% loading is recommended under these
conditions.
Soldering Guidelines
Murata Power Solutions recommends the specifi cations below when installing these
converters. These specifi cations vary depending on the solder type. Exceeding these
specifi cations may cause damage to the product. Your production environment may dif-
fer; therefore please thoroughly review these guidelines with your process engineers.
Wave Solder Operations for through-hole mounted products (THMT)
For Sn/Ag/Cu based solders:
Maximum Preheat Temperature 115° C.
Maximum Pot Temperature 270° C.
Maximum Solder Dwell Time 7 seconds
For Sn/Pb based solders:
Maximum Preheat Temperature 105° C.
Maximum Pot Temperature 250° C.
Maximum Solder Dwell Time 6 seconds
