UNR-1.8/2-D12SM Ver la hoja de datos (PDF) - Murata Power Solutions

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UNR-1.8/2-D12SM

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Murata Power Solutions 

UNR Series

Single Output, Non-Isolated, 1.8/2.5/3.3VOUT 3.6-10W DC/DC Converters

TEMPERATURE DERATING

10

UNR-3.3/3-D5

9

UNR-3.3/3-D5SM

UNR-3.3/3-D12

UNR-3.3/3-D12SM

8

7

6

UNR-2.5/2-D5

UNR-2.5/2-D5SM

5

4

3

UNR-1.8/2-D5

UNR-1.8/2-D5SM

2

1

0

–40 0

40 45 50 55 60 65 70 75 80 85 90 95 100

Ambient Temperature (˚C)

TECHNICAL NOTES

I/O Filtering and Noise Reduction

All D5 models of UNR 3.6-10W Series DC/DC converters achieve their

rated ripple and noise specifications without the use of external input/

output capacitors. The UNR-3.3/3-D12 and D12SM models are tested and

specified with a single, external 22µF input capacitor (minimally rated for

1.5Arms ripple current and 120m ESR).

In critical applications, input/output ripple/noise may be further reduced

by installing additional external I/O caps. Input capacitors, which function

primarily as energy-storage elements, should be selected for bulk capaci-

tance, low ESR and high rms-ripple-current ratings. Output capacitors,

which function more as true filter elements, should be selected for bulk

capacitance, low ESR, and appropriate frequency response. All caps should

have appropriate voltage ratings and be mounted as close to the convert-

ers as possible. Temperature variations for all parameters should obviously

be taken into consideration.

The most effective combination of external I/O capacitors will be a func-

tion of your line voltage and source impedance, as well as your particular

load and layout conditions. Our Applications Engineers will be happy to

recommend potential solutions and can discuss the possibility of our modi-

fying a given device’s internal filtering to meet your specific requirements.

Return Current Paths

The Input Return, Output Return and Logic Ground are all connected to

each other internal to each device. To the extent possible, all load current

should be returned through the Output Return (via low-impedance runs)

and all input current returned through the Input Return. Any control signals

applied to the On/Off Control pin should be referenced to Logic Ground. The

internal trace leading to Logic Ground is not designed to carry high current.

Devices should never be installed in a manner that results in high current

flow through Logic Ground (i.e., the Input/Output Returns should never be

left open or attached via high-impedance connections).

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 Murata Power Solutions UNR Series 3.6-10

Watt DC/DC Converters, you should use slow-blow type fuses with values

no greater than the following.

Model Number

Fuse Value

UNR-1.8/2-D5/-D5SM

1.5 Amps

UNR-2.5/2-D5/-D5SM

2 Amps

UNR-3.3/3-D5/-D5SM

3 Amps

UNR-3.3/3-D12/-D12SM

1.5 Amps

Start-Up Threshold and Undervoltage Shutdown

(UNR-3.3/3-D12 and D12SM only)

Under normal start-up conditions, UNR-3.3/3-D12 and D12SM devices

will not begin to regulate until the ramping input voltage exceeds the Start-

Up Threshold Voltage (typically 10.2V). Once operating, devices will not turn

off until the input voltage drops below the Undervoltage Shutdown/Lockout

limit (typically 9.6V). Subsequent re-start will not occur until the input is

brought back up to the Start-Up Threshold. This built-in hysteresis obviously

avoids any indeterminate on/off conditions at a single voltage.

Start-Up Time

For the three D5 models (that do not have an input turn-on threshold),

the VIN to VOUT Start-Up Time is the interval between the time a step input

is applied to the device and the fully loaded output voltage enters and

remains within its specified accuracy band.

For the UNR-3.3/3-D12 and D12SM, VIN to VOUT Start-Up Time is the

interval between the time at which a rapidly ramping input voltage crosses

the turn-on threshold point and the fully loaded output voltage enters and

remains within its specified accuracy band. 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 to the converter.

The On/Off to VOUT Start-Up Time assumes the converter is turned off via

the On/Off Control with the nominal input voltage already applied to the

converter. The specification defines the interval between the time at which

the converter is turned on and the fully loaded output voltage enters and

remains within its specified accuracy band.

Internal circuit design of the 3.3VOUT models mandates that no voltages

greater than 1.0V be present on the output pins at power-up. 1.8VOUT and

2.5VOUT models can not have voltages greater than 1.2V present on their

output pins at power-up. Failure to comply may result in start-up problems.

www.murata-ps.com/support

MDC_UNR 3.6-10W.C01 Page 5 of 8

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