®

LSN2 Series

Non-isolated, DOSA-SIP, 6/10/16A Selectable-Output DC/DC Converters

www.cd4power.com

Figure 3. Measuring Output Ripple/Noise (PARD)

Figure 2. Measuring Input Ripple Current

Output ripple/noise (also referred to as periodic and random deviations or

PARD) may be reduced below specified limits with the installation of additional

external output capacitors. Output capacitors function as true filter elements

and should be selected for bulk capacitance, low ESR, and appropriate fre-

quency response. Any scope measurements of PARD should be made directly

at the DC/DC output pins with scope probe ground less than 0.5" in length.

All external capacitors should have appropriate voltage ratings and be located

as close to the converters as possible. Temperature variations for all relevant

parameters should be taken into consideration.

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

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

and layout conditions. Our Applications Engineers can recommend potential

solutions and discuss the possibility of our modifying a given device’s internal

filtering to meet your specific requirements. Contact our Applications Engineer-

ing Group for additional details.

Input Fusing

Most applications and or safety agencies require the installation of fuses at

the inputs of power conversion components. The LSN2 Series are not inter-

nally fused. Therefore, if input fusing is mandatory, either a normal-blow or a

slow-blow fuse with a value no greater than twice the maximum input current

calculated at low line with the converter's minimum efficiency should be

installed within the ungrounded input path to the converter.

Safety Considerations

LSN2 SIPs are non-isolated DC/DC converters. In general, all DC/DC's

must be installed, including considerations for I/O voltages and spacing/sepa-

ration requirements, in compliance with relevant safety-agency speci-

fications (usually UL/IEC/EN60950).

In particular, for a non-isolated converter's output voltage to meet SELV

(safety extra low voltage) requirements, its input must be SELV compliant.

If the output needs to be ELV (extra low voltage), the input must be ELV.

Input Overvoltage and Reverse-Polarity Protection

LSN2 SIP Series DC/DC's do not incorporate either input overvoltage or input

reverse-polarity protection. Input voltages in excess of the specified absolute

maximum ratings and input polarity reversals of longer than "instantaneous"

duration can cause permanent damage to these devices.

Start-Up Time

ramping input voltage crosses the lower limit of the specified input volt-

age range 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.

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. See Typical Performance Curves.

Remote Sense

LSN2 Series offer an output sense function. The sense function enables point-

of-use regulation for overcoming moderate IR drops in conductors and/or

cabling. Since these are non-isolated devices whose inputs and outputs usu-

ally share the same ground plane, sense is provided only for the +Output.

The remote sense line is part of the feedback control loop regulating the

DC/DC converter’s output. The sense line carries very little current and

consequently requires a minimal cross-sectional-area conductor. As such,

it is not a low-impedance point and must be treated with care in layout and

cabling. Sense lines should be run adjacent to signals (preferably ground), and

in cable and/or discrete-wiring applications, twisted-pair or similar techniques

and Sense, we recommend installation of a 1000pF capacitor close to the

converter.

The sense function is capable of compensating for voltage drops between the

Power derating (output current limiting) is based upon maximum output

current and voltage at the converter's output pins. Use of trim and sense

functions can cause the output voltage to increase, thereby increasing output

power beyond the LSN2's specified rating. Therefore:

≤ rated output power