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SLES140A—March 2007TVP5147M1PFP
5.2 Designing With PowerPADt Devices
The TVP5147 device is housed in a high-performance, thermally enhanced, 80-terminal PowerPAD package
(TI package designator: 80PFP). Use of the PowerPAD package does not require any special considerations
except to note that the thermal pad, which is an exposed die pad on the bottom of the device, is a metallic
thermal and electrical conductor. Therefore, if not implementing the PowerPAD
PCB features, the use of solder
masks (or other assembly techniques) can be required to prevent any inadvertent shorting by the exposed
thermal pad
of connection etches or vias under the package. The recommended option, however, is not to run
any etches or signal vias under the device, but to have only a grounded thermal land as in the following
explanation. Although the actual size of the exposed die pad may vary, the minimum size required for the
keep-out area for the 80-terminal PFP PowerPAD package is 8 mm × 8 mm.
It is recommended that there be a thermal land, which is an area of solder-tinned-copper, underneath the
PowerPAD package. The thermal land varies in size, depending on the PowerPAD
package being used, the
PCB construction, and the amount of heat that needs to be removed. In addition, the thermal land may or may
not contain numerous thermal vias depending on PCB construction.
Other requirements for using thermal lands and thermal vias are detailed in the TI application note
PowerPADt Thermally Enhanced Package Application Report, (SLMA002), available via the TI Web pages
beginning at URL: http://www.ti.com
For the TVP5147 device, this thermal land must be grounded to the low-impedance ground plane of the
device. This improves not only thermal performance but also the electrical grounding of the device. It is also
recommended that the device ground terminal landing pads be connected directly to the grounded thermal
land. The land size must be as large as possible without shorting device signal terminals. The thermal land
can be soldered to the exposed thermal pad using standard reflow soldering techniques.
While the thermal land can be electrically floated and configured to remove heat to an external heat sink, it
is recommended that the thermal land be connected to the low-impedance ground plane for the device. More
information can be obtained from the TI application note PHY Layout (SLLA020).
PowerPAD is a trademark of Texas Instruments.