LSN16A-D12 Datasheet, PDF (8/13 Pages) Murata Manufacturing Co., Ltd. – Single Output, Non-Isolated, 12VIN, 0.75-5VOUT 16 Amp in DC/DCs SIP Packages

LSN-16A D12 Models
Single Output, Non-Isolated, 12VIN, 0.75-5VOUT
16 Amp in DC/DCs SIP Packages
Voltage Margining
The LSN-T/16-D12 converter can serve as the power source for a production
test environment using voltage margining. This gives the capability to vary
the net output voltage up or down for stress and functional testing of a target
system over the expected power supply voltage range.
Voltage margining requires three external resistors and two switches – the
primary precision trim resistor and two voltage margining resistors. The
switches are typically low on-resistance FET transistors acting as switches.
Devices specifically designed for analog switch applications have effective
closed resistance of a few Ohms and often have a logic gate driving them.
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Figure 5. LSN-T/16-D12 Voltage Margining
After installing the desired trim resistor, the constant voltage output on the
LSN-T/16-D12 may be adjusted up or down a fixed amount by installing sub-
trim voltage margining resistors as shown on the attached circuit. In effect, an
additional voltage divider is switched in one leg at a time to slightly raise or
lower the output voltage. Typical FET switches are the Maxim MAX4643 and
MAX4544 families.
As with the primary trim resistor, by sure to mount these voltage margining
resistors and switches close to the converter with short leads. Be aware that
the effective output voltage is the result of all error sources including the trim
resistor accuracies and temperature coefficients. Also, the resulting trim resis-
tor from the equations is usually not a standard precision value therefore you
may have to parallel two resistors.
CAUTION: Switch in only one resistor at a time to invoke voltage margin-
ing. Do not turn on both resistors simultaneously. Also, do not exceed the total
power output of the converter.
Output Reverse Conduction
Many DC/DC's using synchronous rectification suffer from Output Reverse
Conduction. If those devices have a voltage applied across their output before
a voltage is applied to their input (this typically occurs when another power
supply starts before them in a power-sequenced application), they will either
fail to start or self destruct. In both cases, the cause is the "freewheeling" or
"catch" FET biasing itself on and effectively becoming a short circuit.
LSN D12 SIP DC/DC converters do not suffer from Output Reverse Conduc-
tion. They employ proprietary gate drive circuitry that makes them immune to
applied output voltages.
Thermal Considerations and Thermal Protection
The typical output-current thermal-derating curves shown below enable
designers to determine how much current they can reliably derive from each
model of the LSN D12 SIP's under known ambient-temperature and air-flow
conditions. Similarly, the curves indicate how much air flow is required to reli-
ably deliver a specific output current at known temperatures.
The highest temperatures in LSN D12 SIP's occur at their output inductor,
whose heat is generated primarily by I²R losses. The derating curves were
developed using thermocouples to monitor the inductor temperature and vary-
ing the load to keep that temperature below +110°C under the assorted condi-
tions of air flow and air temperature. Once the temperature exceeds +115°C
(approx.), the thermal protection will disable the converter. Automatic restart
occurs after the temperature has dropped below +110°C.
All but the last two DUT's were vertical-mount models, and the direction of
air flow was parallel to the unit in the direction from pin 11 to pin 1.
As you may deduce from the derating curves and observe in the efficiency
curves on the following pages, LSN D12 SIP's maintain virtually constant
efficiency from half to full load, and consequently deliver very impressive
temperature performance even if operating at full load.
Lastly, when LSN D12 SIP's are installed in system boards, they are obvi-
ously subject to numerous factors and tolerances not taken into account here.
If you are attempting to extract the most current out of these units under
demanding temperature conditions, we advise you to monitor the output-
inductor temperature to ensure it remains below +110°C at all times.
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