TWR-3.3 查看數據表（PDF） - Murata Power Solutions

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TWR-3.3

Isolated, High Reliability 1" x 2" DC/DC Converters

Murata Power Solutions 

Absolute Maximum Ratings

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

Input Reverse-Polarity Protection

See Fuse section

Output Overvoltage Protection

VOUT +20% maximum

Output Current

Current limited. Devices can

withstand sustained output short

circuits without damage.

Storage Temperature

–40 to +120°C

Lead Temperature (soldering 10 sec. max.) +300°C

These are stress ratings. Exposure of devices to any of these conditions may adversely

affect long-term reliability. Proper operation under conditions other than those listed in the

Performance/Functional Specifications Table is not implied.

TECHNICAL NOTES

Load Dependency and Regulation

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.

Input Fusing

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.

Input Voltage

12 Volts

24 Volts

48 Volts

Fuse Value

4 Amps

2 Amps

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.

www.murata-ps.com

Triple Output/TWR Models

Isolated, High Reliability 1" x 2" DC/DC Converters

Input Undervoltage Shutdown and Start-Up Threshold

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.

Ripple Current and Output Noise

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.

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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.

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.

Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000

MDC_TWR22.B02 Page 4 of 9

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