LSN10A-D5 Datasheet, PDF (5/15 Pages) Murata Manufacturing Co., Ltd. – Non-Isolated, 5VIN, 1-3.8VOUT 10 Amp DC/DC In SIP Package

TECHNICAL NOTES
Return Current Paths
The LSN D5 SIP’s are non-isolated DC/DC converters. Their two Common
pins (pins 5 and 6) are connected to each other internally (see Figure 1). To
the extent possible (with the intent of minimizing ground loops), input return
current should be directed through pin 6 (also referred to as –Input or Input
Return), and output return current should be directed through pin 5 (also
referred to as –Output or Output Return). Any on/off control signals applied to
pin 11 (On/Off Control) should be referenced to Common (specifically pin 6).
I/O Filtering and Noise Reduction
All models in the LSN D5 Series are tested and specified with external 22μF
input and output capacitors. These capacitors are necessary to accommo-
date our test equipment and may not be required to achieved desired per-
formance in your application. The LSN D5's are designed with high-quality,
high-performance internal I/O caps, and will operate within spec in most
applications with no additional external components.
In particular, the LSN D5's input capacitors are specified for low ESR and
are fully rated to handle the units' input ripple currents. Similarly, the inter-
nal output capacitors are specified for low ESR and full-range frequency
response. As shown in the Performance Curves, removal of the external
output caps has minimal effect on output noise.
In critical applications, input/output ripple/noise may be further reduced
using filtering techniques, the simplest being the installation of external
I/O caps.
External input capacitors serve primarily as energy-storage devices. They
minimize high-frequency variations in input voltage (usually caused by IR
drops in conductors leading to the DC/DC) as the switching converter draws
pulses of current. Input capacitors should be selected for bulk capacitance
(at appropriate frequencies), low ESR, and high rms-ripple-current ratings.
The switching nature of modern DC/DC's requires that the dc input voltage
source have low ac impedance at the frequencies of interest. Highly induc-
tive source impedances can greatly affect system stability. Your specific
system configuration may necessitate additional considerations.
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 frequency 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 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 Engineering Group for additional details.
Single Output LSN-10A Models
Non-Isolated, 5VIN, 1-3.8VOUT
10 Amp DC/DC In SIP Package
Input Fusing
Most applications and or safety agencies require the installation of fuses at the
inputs of power conversion components. LSN D5 Series DC/DC converters are
not internally fused. Therefore, if input fusing is mandatory, either a normal-
blow or a slow-blow fuse with a value no greater than 15 Amps 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 converters minimum efficiency.
Safety Considerations
LSN D5 SIP'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 D5 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
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
(4.5 Volts) 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
LSN D5 SIP 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
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