LSM16A-W3 Datasheet, PDF (4/12 Pages) Murata Manufacturing Co., Ltd. – Non-Isolated, Wide Input SMT DC/DC Converters

LSM-16A W3 Models
Non-Isolated, Wide Input SMT DC/DC Converters
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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 ⁶
+OUTPUT ⁴
COPPER STRIP
C1
C2
SCOPE
RLOAD
COMMON ³
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
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 LSM W3 Series are not internally
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
LSM 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 spac-
ing/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
LSM 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
ramping 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 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. See Typical Performance
Curves.
Remote Sense
LSM W3 SMT Series DC/DC converters offer an output sense function on pin
6. The sense function enables point-of-use regulation for overcoming mod-
erate 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
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 should be used. To prevent high frequency voltage differences
between VOUT 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 +Output and +Sense pins that do not exceed 10% of VOUT.
[VOUT(+) – Common] – [Sense(+) – Common] b 10%VOUT
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 LSM’s specified rating. Therefore:
(VOUT at pins) x (IOUT) b rated output power
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