UWR-12/1250-D24A-C 查看數據表（PDF） - Unspecified

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UWR-12/1250-D24A-C

Single Output, High-Density, 6 Amp/15 Watt DC/DC Converters

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UWR Models

Single Output, High-Density,

6 Amp/15 Watt DC/DC Converters

Floating Outputs

Since these are isolated DC/DC converters, their outputs are "floating."

Designers will usually use the output Common (pin 6) as the ground/return of

the load circuit. You can, however, use the +Output (pin 4) as ground/return to

effectively reverse the output polarity.

Minimum Output Loading Requirements

1.2 to 5V models employ a synchronous-rectifier design topology. All models

regulate within spec and are stable under no-load conditions. 12/15V models

employ a traditional forward architecture and require 10% loading (125mA for

12V models, 100mA for 15V models) to achieve their listed regulation specs.

12/15V models also have a minimum-load-for-stability requirement (20mA).

For 12/15V models, operation below 20mA or 10% loading will be stable but

regulation may degrade. A 100µF output capacitor is recommended below 10%

loading. Users should verify whether this relaxed regulation will have any effect

on output circuits. If so, add a small load of 10% or greater.

Operation under no-load conditions will not damage 12/15V converters.

However they may not meet all listed specifications.

Filtering and Noise Reduction

All A-Series UWR DC/DC Converters achieve their rated ripple and noise

specifications using the external input and output capacitors specified in the

Performance/Functional Specifications table. In critical applications, input/

output noise may be further reduced by installing additional external I/O caps.

Input capacitors should be selected for bulk capacitance, low ESR and high

rms-ripple-current ratings. Output capacitors should be selected for low ESR and

appropriate frequency response. All caps should have appropriate voltage ratings

and be mounted 2-3 inches from the converter to achieve published ratings. The

most effective combination of external I/O capacitors will be a function of your

particular load and layout conditions.

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 MPS's A-Series UWR 7-15 Watt DC/DC Converters, you

should use fast-blow type fuses with values no greater than the following.

VIN Range

"D12A" Models

"D24A" Models

"D48A" Models

Fuse Value

3 Amps

2 Amps

1 Amp

Maximum Case Temperature

The +100 degree C. maximum outside case temperature specification is based

on much empirical testing on encapsulated units. Those tests show that if

the case exterior can be maintained at or below +100C., the hottest internal

components’ package temperatures will not exceed +128C. because of the

internal temperature gradient to the exterior case. This latter +128C. internal

figure is a safety margin offering more protection for the internal components.

The +100C. case specification must be achieved by the user’s combination of

lower output current and/or higher airflow.

If you attempt any of your own case temperature testing, please be aware of

the heatsinking effect of attaching wired thermocouples to surfaces. An infra-

red camera is a another alternative which avoids the TC heatsinking effect.

But the IR camera must be calibrated frequently and accurately. Remember

too that it is quite difficult to accurately measure airflow right at the converter.

Murata Power Solutions uses a calibrated wind tunnel with large amounts

of data history. Because of thermal time constants, allow plenty of time for

temperature stabilization.

Trimming Output Voltages

These converters have a trim capability (pin 5) that allows users to adjust the

output voltage ±5%. Adjustments to the output voltage can be accomplished

via a trim pot, Figure 2, or a single fixed resistor as shown in Figures 3 and 4.

A single fixed resistor can increase or decrease the output voltage depend-

ing on its connection. Fixed resistors should have an absolute TCR less than

100ppm/°C to minimize sensitivity to changes in temperature.

A single resistor connected from the Trim (pin 5) to the +Output (pin 4), see

Figure 3, will decrease the output voltage. A resistor connected from the Trim

(pin 5) to Output Common (pin 6) will increase the output voltage.

Trim adjustment greater than 5% can have an adverse effect on the con-

verter's performance and is not recommended.

1

+VIN

2

–VIN

3 ON/OFF

CONTROL

4

+VOUT

5

TRIM

6

COMMON

20kΩ

5-22

Turns

LOAD

Figure 2. Trim Connections Using A Trim Pot

1

+VIN

2

–VIN

3 ON/OFF

CONTROL

4

+VOUT

5

TRIM

RTRIM DOWN

LOAD

6

COMMON

Figure 3. Trim Connections To Decrease Output Voltage Using Fixed Resistors

1

+VIN

2

–VIN

3 ON/OFF

CONTROL

4

+VOUT

5

TRIM

6

COMMON

LOAD

RTRIM UP

Figure 4. Trim Connections To Increase Output Voltage Using Fixed Resistors

www.murata-ps.com/support

MDC_UWR_7-15.I03  Page 4 of 13

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