THS3491 Datasheet, PDF (19/28 Pages) Texas Instruments – 900-MHz, High-Power Output, Current Feedback Amplifier

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THS3491
SBOS875 – AUGUST 2017
Layout Guidelines (continued)
11.1.1 PowerPAD™ Design Considerations (DDA Package Only)
The THS3491 is available in a thermally-enhanced PowerPAD package. These packages are constructed using
a downset leadframe on which the die is mounted, as shown in the (a) and (b) sections of Figure 15. This
arrangement results in the lead frame being exposed as a thermal pad on the underside of the package, a shown
in Figure 15(c). Because this thermal pad has direct thermal contact with the die, excellent thermal performance
can be achieved by providing a good thermal path away from the thermal pad. Devices such as the THS3491
have no electrical connection between the PowerPAD and the die.
The PowerPAD package allows for both assembly and thermal management in one manufacturing operation.
During the surface-mount solder operation (when the leads are being soldered), the thermal pad can also be
soldered to a copper area underneath the package. Through the use of thermal paths within this copper area,
heat can be conducted away from the package into either a ground plane or other heat-dissipating device.
The PowerPAD package represents a breakthrough in combining the small area and ease of assembly of
surface mount with the, heretofore, awkward mechanical methods of heatsinking.
DIE
Side View (a)
DIE
End View (b)
Thermal
Pad
Bottom View (c)
Figure 15. Views of Thermally Enhanced Package
Although there are many ways to properly heatsink the PowerPAD package, the following section illustrates the
recommended approach.
11.1.1.1 PowerPAD™ Layout Considerations
The DDA package top-side etch and via pattern is shown in Figure 16.
0.300
(7,62)
0.100
(2,54)
0.035
(0,89)
0.010
(0,254)
0.026
(0,66)
0.060
(1,52)
0.140
(3,56)
0.060
(1,52)
0.030
(0,732)
0.176
(4,47)
0.050
(1,27)
0.010
(0.254)
vias
0.035
(0,89)
0.080
(2,03)
All Units in inches (millimeters)
Figure 16. DDA PowerPAD™ PCB Etch and Via Pattern
1. Use etch for the leads as well as etch for the thermal pad.
2. Drill 13 holes in the area of the thermal pad. These holes must be 0.01 inch (0.254 mm) in diameter. Keep
them small so that solder wicking through the holes is not a problem during reflow.
3. Additional vias may be placed anywhere along the thermal plane outside of the thermal pad area, and help
dissipate the heat generated by the THS3491 device. These additional vias may be larger than the 0.01-inch
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