Datasheet

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DIE
Side View (a)
DIE
End View (b)
Bottom View (c)
0.144
0.0195
0.144
0.010
vias
Pin 1
Top View
0.012
0.030
0.0705
0.015
0.0095
0.049
0.032
0.0245
PowerPAD™ PCB LAYOUT
THS4302
SLOS403H – OCTOBER 2002 – REVISED AUGUST 2006
The PowerPAD package represents a breakthrough that wicking is not a problem.
in combining the small area and ease of assembly of
4. Connect all holes to the internal ground plane.
surface mount with the heretofore awkward
5. When connecting these holes to the ground
mechanical methods of heatsinking.
plane, do not use the typical web or spoke via
connection methodology. Web connections have
a high thermal resistance connection that is
useful for slowing the heat transfer during
soldering operations. This resistance makes the
soldering of vias that have plane connections
easier. In this application, however, low thermal
resistance is desired for the most efficient heat
transfer. Therefore, the holes under the IC
PowerPAD package should make their
Figure 49. Views of Thermally Enhanced Package
connection to the internal ground plane, with a
complete connection around the entire
Although there are many ways to properly heatsink
circumference of the plated-through hole.
the PowerPAD package, the following steps illustrate
6. The top-side solder mask should leave the
the recommended approach.
terminals of the package and the thermal pad
area with its five holes exposed. The bottom-side
solder mask should cover the five holes of the
thermal pad area. This prevents solder from
being pulled away from the thermal pad area
during the reflow process.
7. Apply solder paste to the exposed thermal pad
area and all of the IC terminals.
8. With these preparatory steps in place, the IC is
simply placed in position and run through the
solder reflow operation as any standard
surface-mount component. This results in a part
that is properly installed.
The next consideration is the package constraints.
The two sources of heat within an amplifier are
quiescent power and output power. The designer
should never forget about the quiescent heat
generated within the device, especially multi-amplifier
devices. Because these devices have linear output
Figure 50. PowerPAD PCB Etch and Via Pattern
stages (Class AB), most of the heat dissipation is at
low output voltages with high output currents.
The other key factor when dealing with power
dissipation is how the devices are mounted on the
CONSIDERATIONS
PCB. The PowerPAD devices are extremely useful
1. Prepare the PCB with a top side etch pattern as
for heat dissipation. But, the device should always be
shown in Figure 50 . There should be etch for the
soldered to a copper plane to fully use the heat
leads as well as etch for the thermal pad.
dissipation properties of the PowerPAD. The SOIC
2. Place five holes in the area of the thermal pad.
package, on the other hand, is highly dependent on
They holes should be 13 mils in diameter. Keep
how it is mounted on the PCB. As more trace and
them small so that solder wicking through the
copper area is placed around the device, Θ
JA
holes is not a problem during reflow.
decreases and the heat dissipation capability
increases. For a single package, the sum of the RMS
3. Additional vias may be placed anywhere along
output currents and voltages should be used to
the thermal plane outside of the thermal pad
choose the proper package.
area. They help dissipate the heat generated by
the IC. These additional vias may be larger than
the 13-mil diameter vias directly under the
thermal pad. They can be larger because they
are not in the thermal pad area to be soldered, so
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