PZT751T1 View Datasheet(PDF) - Motorola => Freescale
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PZT751T1 Datasheet PDF : 6 Pages
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PZT751T1
INFORMATION FOR USING THE SOT-223 SURFACE MOUNT PACKAGE
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
Surface mount board layout is a critical portion of the total
design. The footprint for the semiconductor packages must
be the correct size to insure proper solder connection
interface between the board and the package. With the
correct pad geometry, the packages will self align when
subjected to a solder reflow process.
0.15
3.8
0.079
2.0
0.091
2.3
0.091
2.3
0.079
2.0
0.059
1.5
0.059
1.5
0.059
1.5
SOT-223
0.248
6.3
inches
mm
SOT-223 POWER DISSIPATION
The power dissipation of the SOT-223 is a function of the
pad size. This can vary from the minimum pad size for
soldering to a pad size given for maximum power dissipation.
Power dissipation for a surface mount device is determined
by TJ(max), the maximum rated junction temperature of the
die, RθJA, the thermal resistance from the device junction to
ambient, and the operating temperature, TA. Using the
values provided on the data sheet for the SOT-223 package,
PD can be calculated as follows:
PD =
TJ(max) – TA
RθJA
The values for the equation are found in the maximum
ratings table on the data sheet. Substituting these values into
the equation for an ambient temperature TA of 25°C, one can
calculate the power dissipation of the device which in this
case is 1.5 watts.
PD = 150°C – 25°C = 1.5 watts
83.3°C/W
The 83.3°C/W for the SOT-223 package assumes the use
of the recommended footprint on a glass epoxy printed circuit
board to achieve a power dissipation of 1.5 watts. There are
other alternatives to achieving higher power dissipation from
the SOT-223 package. One is to increase the area of the
collector pad. By increasing the area of the collector pad, the
power dissipation can be increased. Although the power
dissipation can almost be doubled with this method, area is
taken up on the printed circuit board which can defeat the
purpose of using surface mount technology. A graph of RθJA
versus collector pad area is shown in Figure 1.
160
140
° 120
100
Board Material = 0.0625″
G-10/FR-4, 2 oz Copper
0.8 Watts
1.25 Watts*
TA = 25°C
1.5 Watts
*Mounted on the DPAK footprint
80
0.0
0.2
0.4
0.6
0.8
1.0
A, Area (square inches)
Figure 1. Thermal Resistance versus Collector
Pad Area for the SOT-223 Package (Typical)
Another alternative would be to use a ceramic substrate or
an aluminum core board such as Thermal Clad™. Using a
board material such as Thermal Clad, an aluminum core
board, the power dissipation can be doubled using the same
footprint.
Motorola Small–Signal Transistors, FETs and Diodes Device Data
3
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