LSN16A-W3 Datasheet, PDF (4/8 Pages) Murata Manufacturing Co., Ltd. – Non-Isolated, 3-5.5VIN, 0.75-3.3VOUT 16 Amp DC/DC Converters

Single Output LSN-W3 Models
Non-Isolated, 3-5.5VIN, 0.75-3.3VOUT
16 Amp DC/DC Converters
TO
OSCILLOSCOPE
+
VIN
–
LBUS
CBUS
CURRENT
PROBE
CIN
+INPUT
CIN = 2 x 100μF, ESR < 700m7 @ 100kHz
CBUS = 1000μF, ESR < 100m7 @ 100kHz
LBUS = 1μH
COMMON
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
+SENSE
+OUTPUT
COPPER STRIP
C1
C2
SCOPE
RLOAD
COMMON
COPPER STRIP
C1 = NA
C2 = 22μF TANTALUM
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3. Measuring Output Ripple/Noise (PARD)
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.
You should add only enough output capacitance to attenuate the noise to
your desired level. Large amounts of output capacitance cause poor dynamic
response (step load changes, etc.). Too great an output capacitor can make the
converter oscillate (actually increasing the noise!) while substantial capaci-
tance which is less than the oscillation threshold can still cause ringing and
overshoot. Finally, you must use less output capacitance if the cap is a low
ESR type (OSCON, etc.).
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 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 LSN W3 Series are not inter-
nally fused. Therefore, if input fusing is mandatory, either a normal-blow or a
fast-blow fuse with a value no greater than twice the maximum input current
should be installed within the ungrounded input path to the converter.
As a rule of thumb however, we recommend to use a normal-blow or
slow-blow fuse with a typical value of about twice the maximum input current,
calculated at low line with the converter’s minimum efficiency.
Safety Considerations
LSN W3 SMT’s are non-isolated DC/DC converters. In general, all DC/DC’s must
be installed, including considerations for I/O voltages and spacing/separation
requirements, in compliance with relevant safety-agency specifications (usually
UL/IEC/EN60950-1).
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
LSN W3 SMT Series DC/DC’s do not incorporate either input overvoltage
or input reverse-polarity protection. Input voltages in excess of the speci-
fied absolute maximum ratings and input polarity reversals of longer than
“instantaneous” duration can cause permanent damage to these devices.
Start-Up Time
The VIN to VOUT Start-Up Time is the interval between the time at which a ramp-
ing input voltage crosses the lower limit of the specified input voltage 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 volt-
age 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. See Typical Performance Curves.
Remote Sense
LSN W3 SMT Series DC/DC converters offer an output sense function on pin 3.
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 usually 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 conse-
quently 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 should
be used. To prevent high frequency voltage differences between VOUT and
Sense, we recommend installation of a 1000pF capacitor close to the converter.
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