5.2 Designing With PowerPADt
The TVP5146 device is housed in a high-performance, thermally enhanced, 80-pin PowerPAD package (TI package
designator: 80PFP). Use of the PowerPAD package does not require any special considerations except to note that
the PowerPAD, 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)
may be required to prevent any inadvertent shorting by the exposed PowerPAD 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 explained below. Although the actual size of the exposed die pad may vary, the
minimum size required for the keepout area for the 80-terminal PFP PowerPAD package is 8 mm x 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,
TI literature number SLMA002, available via the TI Web pages
beginning at URL:
http://www.ti.com
For the TVP5146 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 may be soldered to the exposed
PowerPAD using standard reflow soldering techniques.
While the thermal land may 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 may be obtained from the TI application note
PHY Layout,
TI literature number SLLA020.
PowerPAD is a trademark of Texas Instruments.
5−2
TI [ TEXAS INSTRUMENTS ]
