LSM10A-D3 Datasheet, PDF (6/13 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
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/54054
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K7
 
4URNS
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Figure 6. Trim Connections Using a Trimpot
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4RIM
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4RIM
5P
Note:
Install either a fixed
trim-up resistor
or a fixed trim-down
resistor depending upon
desired output voltage.
Figure 7. Trim Connections Using Fixed Resistors
Model
LSM-1/10-D3
LSM-1.2/10-D3
LSM-1.5/10-D3
LSM-1.8/10-D3
LSM-2/10-D3
LSM-2.5/10-D3
Trim Equations
Trim Equations
1.62(VO – 0.8)
RT_DOWN (k7) =
1 – VO
–1
1.296
RT_UP (k7) = _{VO – 1} – 1
2.49(VO – 0.8)
RT_DOWN (k7) =
1.2 – VO
– 2.37
1.992
RT_UP (k7) = _{VO – 1.2} – 2.37
2.37(VO – 0.8)
RT_DOWN (k7) =
VO _NOM – VO
– 4.99
1.896
RT_UP (k7) = _{VO – VO NOM} – 4.99
Note: Resistor values are in k7. Accuracy of adjustment is subject to
tolerances of resistors and factory-adjusted, initial output accuracy.
VO = desired output voltage. VONOM = nominal output voltage.
Note: LSM-0.8/10-D3 is not trimmable.
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.
LSM D3 SMT 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 LSM D3 SMT's under known ambient-temperature and air-flow
conditions. Similarly, the curves indicate how much air flow is required to
reliably deliver a specific output current at known temperatures.
The highest temperatures in LSM D3 SMT'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
varying the load to keep that temperature below +110°C under the assorted
conditions 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.
As you may deduce from the derating curves and observe in the efficiency
curves on the following pages, LSM D3 SMT's are more efficient at lower
current levels. Also I²R losses in the output inductor are significantly less at
lower current levels. Consequently, LSN-D3 SMT's deliver very impressive
temperature performance if operating at less than full load.
Lastly, when LSM D3 SMT'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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MDC_LSM-10A D3.B01 Page 6 of 13