Datasheet

ManualsBrandsMURATA POWER SOLUTIONS ManualsPSU ComponentsDC/DC converter (print) 3 A 15 W No. of outputs: 1 x

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 routinely or accidentally exceed these Derating guidelines,

the converter may have an unplanned Over Temperature shut down. Also, these

graphs are all collected at slightly above Sea Level altitude. Be sure to reduce

the derating for higher density 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 par-

ticularly 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 ramping up 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. A short circuit can be tolerated indeﬁ nitely.

Remote On/Off Control

The remote On/Off Control can be ordered with either 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 left open 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 appropriate signal current

when brought low and withstand appropriate 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. Proper wiring of the Sense inputs will improve these factors under

capacitive load.

The maximum rated output capacitance and ESR speciﬁ cation is given for a

capacitor installed immediately adjacent to the converter. Any extended output

wiring, smaller wire gauge or less ground plane may tolerate somewhat higher

capacitance. Also, capacitors with higher ESR may use a larger capacitance.

Pre-Biased Startup

Some sections have external power already partially applied (possibly because

of earlier power sequencing) before POL power up. Or leakage power is pres-

ent so that the DC/DC converter must power up into an existing output voltage.

This power may either be stored in an external bypass capacitor or supplied by

an active source. These converters include a pre-bias startup mode to prevent

initialization problems.

This “pre-biased” condition can also occur with some types of program-

mable logic or because of blocking diode leakage or small currents passed

through forward biased ESD diodes. This feature is variously called “mono-

tonic” because the voltage does not decay or produce a negative transient

once the input power is applied and startup begins.

C1 = 1µF

C2 = 10µF

LOAD 2-3 INCHES (51-76mm) FROM MODULE

LOAD

SCOPE

+OUTPUT

+SENSE

-OUTPUT

Figure 3. Measuring Output Ripple and Noise (PARD)

OKX-T/3-D12 Series

Adjustable 3-Amp SIP Non-Isolated DC/DC Converters

MDC_OKX-T/3-D12 Series.A01 Page 14 of 15