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LSM10A-D3 Datasheet, PDF (4/13 Pages) Murata Manufacturing Co., Ltd. – Single Output, Non-Isolated, 3.3VIN, 0.8-2.5VOUT 10 Amp DC/DC’s in SMT Packages
LSM-10A D3 Models
Single Output, Non-Isolated, 3.3VIN, 0.8-2.5VOUT
10 Amp DC/DC’s in SMT Packages
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 appro-
priate 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.
Input Overvoltage and Reverse-Polarity Protection
LSM D3 SMT 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 "instan-
taneous" duration can cause permanent damage to these devices.
Start-Up Time
+SENSE 6
4
+OUTPUT
COPPER STRIP
C1
C2
SCOPE
RLOAD
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 (3 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.
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 solu-
tions and discuss the possibility of our modifying a given device’s internal filter-
ing to meet your specific requirements. Contact our Applications Engineering
Group for additional details.
Input Fusing
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 D3 SMT Series DC/DC converters offer an output sense function on
pin 6. 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
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 tech-
niques should be used. To prevent high frequency voltage differences between
VOUT and Sense, we recommend installation of a 1000pF capacitor close to
the converter.
Most applications and or safety agencies require the installation of fuses at
the inputs of power conversion components. LSM D3 Series DC/DC convert-
ers 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 17 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
LSM D3 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 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.
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 cur-
rent and voltage at the converter's output pins. Use of trim and sense func-
tions 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
The internal 10.57resistor between +Sense and +Output (see Figure 1)
serves to protect the sense function by limiting the output current flowing
through the sense line if the main output is disconnected. It also prevents
output voltage runaway if the sense connection is disconnected.
Note: If the sense function is not used for remote regulation, +Sense
(pin 6) must be tied to +Output (pin 4) at the DC/DC converter pins.
For the "B" model number option (sense pad removed), the sense is internally
connected to +VOUT.
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Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
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