Triple Output/TWR Models
Isolated, High Reliability 1" x 2" DC/DC Converters
Input Undervoltage Shutdown and Start-Up Threshold
Absolute Maximum Ratings
Under normal start-up conditions, devices will not begin to regulate
until the ramping-up input voltage exceeds the Start-Up Threshold Voltage.
Once operating, devices will not turn off until the instantaneous input
voltage drops below the Undervoltage Shutdown limit. Subsequent restart
will not occur until the input is brought back up to the Start-Up Threshold.
This built-in hysteresis avoids any unstable on/off situations occurring at a
single input voltage. However, you should be aware that poorly regulated
input sources and/or higher input impedance sources (including long power
leads) which have outputs near these voltages may cause cycling of the
converter outputs.
Input Voltage:
Continuous or transient
12V Models
24V Models
48V Models
–0.3V minimum or +18V maximum
–0.3V minimum or +36V maximum
–0.3V minimum or +75V maximum
On/Off Control (Pin 1)
–0.3V minimum or +VIN maximum
See Fuse section
Input Reverse-Polarity Protection
Output Overvoltage Protection
Output Current
VOUT +20% maximum
Current limited. Devices can
withstand sustained output short
circuits without damage.
Storage Temperature
–40 to +120°C
Ripple Current and Output Noise
Lead Temperature (soldering 10 sec. max.) +300°C
These are stress ratings. Exposure of devices to any of these conditions may adversely
All TWR converters are tested and specified for input reflected ripple cur-
rent (also called Back Ripple Current) and output noise using specified filter
components and test circuit layout as shown in the figures below. Input
capacitors must be selected for low ESR, high AC current-carrying capabil-
ity at the converter’s switching frequency and adequate bulk capacitance.
The switching nature of DC/DC converters requires this low AC impedance
to absorb the current pulses reflected back from the converter’s input.
affect long-term reliability. Proper operation under conditions other than those listed in the
Performance/Functional Specifications Table is not implied.
T E C H N I C A L N O T E S
Load Dependency and Regulation
4/
The high voltage bipolar output section derives its regulation as a slave
to the low voltage unipolar output. Be aware that large load changes on
the unipolar section will change the voltage somewhat on the bipolar
section. To retain proper regulation, the bipolar voltage section must have
a minimum load of at least 10% of rated full output. With this minimal
load (or greater), the high voltage bipolar section will meet all its regula-
tion specifications. If there is no load, the output voltage may exceed the
regulation somewhat.
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Input Fusing
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Certain applications and/or safety agencies require fuses at the inputs
of power conversion components. Fuses should also be used if there is the
possibility of sustained, non-current limited reverse input polarity. DATEL
recommends slow-blow type fuses approximately twice the maximum
input current at nominal input voltage but no greater than 5 Amps. Install
these fuses in the high side (ungrounded input) power lead to the converter.
Figure 2. Measuring Input Ripple Current
Output Overcurrent Detection
Overloading the power converter’s output for extended periods (but not a
short circuit) at high ambient temperatures may overheat the output com-
ponents and possibly lead to component failure. Brief moderate overcurrent
operation (such as charging up reasonably-sized external bypass capacitors
when first starting) will not cause problems. The TWR series include current
limiting to avoid heat damage. However, you should remove a sustained
overcurrent condition promptly as soon as it is detected. Combinations of
low airflow and/or high ambient temperature for extended periods may
cause overheating even though current limiting is in place.
Input Voltage
12 Volts
Fuse Value
4 Amps
24 Volts
2 Amps
48 Volts
1 Amp
Input Source Impedance
The external source supplying input power must have low AC imped-
ance. Failure to insure adequate low AC impedance may cause stability
problems, increased output noise, oscillation, poor settling and aborted
start-up. The converter’s built-in front end filtering will be sufficient in most
applications. However, if additional AC impedance reduction is needed,
consider adding an external capacitor across the input terminals mounted
close to the converter. The capacitor should have low internal Equivalent
Series Resistance (ESR) and low inductance. Often, two or more capaci-
tors are used in parallel. A ceramic capacitor gives very low AC impedance
while a parallel electrolytic capacitor offers improved energy storage.
Current Return Paths
Make sure to use adequately sized conductors between the output
load and the Common connection. Avoid simply connecting high current
returns only through the ground plane unless there is adequate copper
thickness. Also, route the input and output circuits directly to the Common
pins. Failure to observe proper wiring may cause instability, poor regulation,
increased noise, aborted start-up or other undefined operation.
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_TWR22.B02 Page 4 of 9
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