Specification Notes, Cont.:

(7)

Please observe the voltage input and output specifications in the Voltage Range Graph on page 7.

(8)

Output noise may be further reduced by adding an external filter. At zero output current, the output may

contain low frequency components which exceed the ripple specification. The output may be operated

indefinitely with no load.

(9)

All models are fully operational and meet published specifications, including “cold start” at –40˚ C.

(10) Regulation specifications describe the deviation as the line input voltage or output load current is varied

from a nominal midpoint value to either extreme.

(11) Other input or output voltage ranges will be reviewed under scheduled quantity special order.

(12) Maximum PC board temperature is measured with the sensor in the center of the converter.

(13) Do not exceed maximum power specifications when adjusting the output trim.

(14) The maximum output capacitive loads depend on the the Equivalent Series Resistance (ESR) of the external

output capacitor and, to a lesser extent, the distance and series impedance to the load. Larger caps will

reduce output noise but may change the transient response. Newer ceramic caps with very low ESR may

require lower capacitor values to avoid instability. Thoroughly test your capacitors in the application. Please

refer to the Output Capacitive Load Application Note.

(15) Do not allow the input voltage to degrade lower than the input undervoltage shutdown voltage at all times.

Otherwise, you risk having the converter turn off. The undervoltage shutdown is not latching and will

attempt to recover when the input is brought back into normal operating range.

(16) The outputs are not intended to sink appreciable reverse current.

(17) “Hiccup” overcurrent operation repeatedly attempts to restart the converter with a brief, full-current output.

If the overcurrent condition still exists, the restart current will be removed and then tried again. This short

current pulse prevents overheating and damaging the converter. Once the fault is removed, the converter

immediately recovers normal operation.

Output Voltage Adustment

The output voltage may be adjusted over a limited range by connecting an

external trim resistor (Rtrim) between the Trim pin and Ground. The Rtrim

resistor must be a 1/10 Watt precision metal film type, ±0.5% accuracy or

better with low temperature coefficient, ±100 ppm/oC. or better. Mount the

resistor close to the converter with very short leads or use a surface mount

trim resistor.

In the tables below, the calculated resistance is given. Do not exceed the

specified limits of the output voltage or the converter’s maximum power

rating when applying these resistors. Also, avoid high noise at the Trim

input. However, to prevent instability, you should never connect any capaci-

tors to Trim.

:) = _____________

1.2

OKL-T/3-W5

Output Voltage

Calculated Rtrim (KΩ)

3.3 V.

0.44

2.5 V.

0.63

2.0 V.

0.86

1.8 V.

1.0

1.5 V.

1.33

1.2 V.

2.0

1.0 V.

3.0

0.6 V.

∞ (open)

Resistor Trim Equation, OKL-T/3-W5 models:

Input Fusing

Certain applications and/or safety agencies may require fuses at the inputs

of power conversion components. Fuses should also be used when there

is the possibility of sustained input voltage reversal which is not current-

limited. For greatest safety, we recommend a fast blow fuse installed in the

ungrounded input supply line.

The installer must observe all relevant safety standards and regulations.

For safety agency approvals, install the converter in compliance with the

end-user safety standard, i.e. IEC/EN/UL 60950-1.

Input Under-Voltage Shutdown and Start-Up Threshold

Under normal start-up conditions, converters will not begin to regulate

properly until the ramping-up input voltage exceeds and remains at the

Start-Up Threshold Voltage (see Specifications). Once operating, convert-

ers will not turn off until the input voltage drops below the Under-Voltage

Shutdown Limit. Subsequent restart will not occur until the input voltage

rises again above the Start-Up Threshold. This built-in hysteresis prevents

any unstable on/off operation at a single input voltage.

Users should be aware however of input sources near the Under-Voltage

Shutdown whose voltage decays as input current is consumed (such as

capacitor inputs), the converter shuts off and then restarts as the external

capacitor recharges. Such situations could oscillate. To prevent this, make

sure the operating input voltage is well above the UV Shutdown voltage AT

ALL TIMES.

Start-Up Time

Assuming that the output current is set at the rated maximum, the Vin to

Vout Start-Up Time (see Specifications) is the time interval between the

point when the ramping input voltage crosses the Start-Up Threshold and

the fully loaded regulated output voltage enters and remains within its

specified accuracy band. Actual measured times will vary with input source

impedance, external input capacitance, input voltage slew rate and final

value of the input voltage as it appears at the converter.

These converters include a soft start circuit to moderate the duty cycle of

its PWM controller at power up, thereby limiting the input inrush current.

The On/Off Remote Control interval from On command to Vout regulated

assumes that the converter already has its input voltage stabilized above

the Start-Up Threshold before the On command. The interval is measured

from the On command until the output enters and remains within its

specified accuracy band. The specification assumes that the output is fully

loaded at maximum rated current. Similar conditions apply to the On to Vout

regulated specification such as external load capacitance and soft start

circuitry.

Recommended Input Filtering

The user must assure that the input source has low AC impedance to

provide dynamic stability and that the input supply has little or no inductive

content, including long distributed wiring to a remote power supply. The

converter will operate with no additional external capacitance if these

conditions are met.

APPLICATION NOTES

OKL-T/3-W5 Series

Programmable Output 3-Amp iLGA SMT PoLs

www.murata-ps.com

email: sales@murata-ps.com

12 May 2010

MDC_OKL-T/3-W5 Series.A03 Page 5 of 15