CMPWR280TN Ver la hoja de datos (PDF) - ON Semiconductor
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CMPWR280TN Datasheet PDF : 11 Pages
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CMPWR280
TYPICAL THERMAL CHARACTERISTICS
Thermal dissipation of junction heat consists primarily of
two paths in series. The first path is the junction to the case
(qJC) thermal resistance which is defined by the package
style, and the second path is the case to ambient (qCA)
thermal resistance, which is dependent on board layout.
The overall junction to ambient (qJA) thermal resistance
is equal to:
qJA + qJC ) qCA
For a given package style and board layout, the operating
junction temperature is a function of junction power
dissipation PJUNC, and the ambient temperature, resulting in
the following thermal equation:
TJUNC + TAMB ) PJUNC(qJC) ) PJUNC(qCA)
+ TAMB ) PJUNC(qJA)
The CMPWR280TO is housed in a TO−263 5−lead
package, which provides a qJC of 3C/W. The ground tab is
soldered down to the PCB. When the device is mounted on
a double−sided printed circuit board with two square inches
of copper allocated for “heat spreading”, the resulting qJA is
25C/W.
Based on a maximum power dissipation of 2.85 W
(1.9 V x 1.5 A) with an ambient of 70C the resulting
junction temperature will be:
TJUNC + TAMB ) PJUNC(qJA)
+ 70° C ) 2.85 W (25° CńW)
+ 70° C ) 71° C + 141° C
All thermal characteristics of the CMPWR280TO were
measured using a double−sided board with two square
inches of copper area connected to the GND pins for “heat
spreading”.
Measurements showing performance up to junction
temperature of 125C were performed under light load
conditions (5 mA). This allows the ambient temperature to
be representative of the internal junction temperature.
NOTE:
The use of multi−layer board construction with
power planes will further enhance the thermal
performance of the package. In the event of no
copper area being dedicated for heat spreading,
a multi−layer board construction will typically
provide the CMPWR280TO with an overall qJA
of 25C/W which allows up to 2.5 W to be
safely dissipated.
Output Voltage vs. Temperature. Output Voltage vs.
Temperature shows the regulator VOUT performance up to
the maximum rated junction temperature. The overall 125C
variation in junction temperature causes an output voltage
change of about 25 mV.
Figure 19. Output Voltage vs. Temperature
Output Voltage (Rated) vs. Temperature. Output
Voltage (Rated) vs. Temperature shows the regulator steady
state performance when fully loaded (1.5 A) in an ambient
temperature up to the rated maximum of 70C. The output
variation at maximum load is approximately 13 mV across
the normal temperature range.
Figure 20. Output Voltage (Rated) vs. Temperature
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