ADS1274
ADS1278
www.ti.com
SBAS367–JUNE 2007
PowerPAD PCB Layout Considerations
The via connections to the thermal pad and internal
ground plane should be plated completely around the
hole, as opposed to the typical web or spoke thermal
relief connection. Plating entirely around the thermal
via provides the most efficient thermal connection to
the ground plane.
Figure 92 shows the recommended layer structure for
thermal management when using
a PowerPad
package on a 4-layer PCB design. Note that the
thermal pad is placed on both the top and bottom
sides of the board. The ground plane is used as the
heatsink, while the power plane is thermally isolated
from the thermal vias.
Additional PowerPAD Package Information
Texas Instruments publishes the PowerPAD
Thermally Enhanced Package Application Report (TI
literature number SLMA002), available for download
Figure 93 shows the required thermal pad etch
pattern for the HTQFP-64 package used for the
ADS1274. Nine 13mil (0.33mm) thermal vias plated
with 1 ounce of copper are placed within the thermal
pad area for the purpose of connecting the pad to the
ground plane layer. The ground plane is used as a
heatsink in this application. It is very important that
the thermal via diameter be no larger than 13mils in
order to avoid solder wicking during the reflow
process. Solder wicking results in thermal voids that
reduce heat dissipation efficiency and hampers heat
flow away from the IC die.
at www.ti.com, that provides
a more detailed
discussion of PowerPAD design and layout
considerations. Before attempting a board layout with
the ADS1274, it is recommended that the hardware
engineer and/or layout designer be familiar with the
information contained in this document.
Package
Thermal Pad
Component
Traces
13mils (0.33mm)
Component (top) Side
Ground Plane
Thermal Via
Power Plane
Thermal Isolation
(power plane only)
Solder (bottom) Side
Package
Thermal Pad
(bottom trace)
Figure 92. Recommended PCB Structure for a 4-Layer Board
40
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