Datasheet

45
40
35
30
25
20
ThermalResistance, ( C/W)°
JA
0 1
q
2 3 4 5
CopperArea(inches )
2
OPA564
SurfaceMountPackage
2ozcopper
THERMALRESISTANCEvsCIRCUITBOARDCOPPERAREA
6
5
4
3
2
1
0
PowerDissipationinPackage(W)
0 25 50
75
100 125
Temperature( C)
°
NoCopper
Copper,Soldered
withoutForcedAir
Copper,Soldered
with200LFMAirflow
MAXIMUMPOWERDISSIPATIONvsTEMPERATURE
OPA564
www.ti.com SBOS372E –OCTOBER 2008– REVISED JANUARY 2011
For applications with limited board size, refer to THERMALLY-ENHANCED PowerPAD
Figure 47 for the approximate thermal resistance PACKAGE
relative to heatsink area. Increasing heatsink area
The OPA564 uses the HSOP-20 PowerPAD DWP
beyond 2in
2
provides little improvement in thermal
and DWD packages, which are thermally-enhanced,
resistance. To achieve the 33°C/W shown in the
standard size IC packages. These packages enhance
Electrical Characteristics, a 2oz copper plane size of
power dissipation capability significantly and can be
9in
2
was used. The PowerPAD package is well-suited
easily mounted using standard printed circuit board
for continuous power levels from 2W to 4W,
(PCB) assembly techniques, and can be removed
depending on ambient temperature and heatsink
and replaced using standard repair procedures.
area. The addition of airflow also influences maximum
power dissipation, as Figure 48 illustrates. Higher
The DWP PowerPAD package is designed so that
power levels may be achieved in applications with a
the leadframe die pad (or thermal pad) is exposed on
low on/off duty cycle, such as remote meter reading.
the bottom of the IC, as shown in Figure 49a; the
DWD PowerPAD package has the exposed pad on
the top side of the package, as shown in Figure 49b.
The thermal pad provides an extremely low thermal
resistance (q
JC
) path between the die and the exterior
of the package.
PowerPAD packages with exposed pad down are
designed to be soldered directly to the PCB, using
the PCB as a heatsink. Texas Instruments does not
recommend the use of the of a PowerPAD package
without soldering it to the PCB because of the risk of
lower thermal performance and mechanical integrity.
In addition, through the use of thermal vias, the
bottom-side thermal pad can be directly connected to
a power plane or special heatsink structure designed
into the PCB. The PowerPAD should be at the same
voltage potential as V–. Soldering the bottom-side
PowerPAD to the PCB is always required, even with
applications that have low power dissipation. It
Figure 47. Thermal Resistance vs Circuit Board
provides the necessary thermal and mechanical
Copper Area
connection between the leadframe die and the PCB.
Pad-up PowerPAD packages should have
appropriately designed heatsinks attached. Because
of the variation and flexible nature of this type of heat
sink, additional details should come from the specific
manufacturer of the heatsink.
Figure 48. Maximum Power Dissipation vs
Temperature
© 2008–2011, Texas Instruments Incorporated Submit Documentation Feedback 23
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