TSB41BA3APFP datasheet(30/66 Pages) TI

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TSB41BA3A

IEEE 1394b THREEPORT CABLE TRANSCEIVER/ARBITER

SLLS618B − JUNE 2004 − REVISED AUGUST 2004

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

designing with PowerPAD



The TSB41BA3A is housed in a high performance, thermally enhanced, 80-terminal PFP PowerPAD



package. 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 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 to not 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 maximum size required for the keepout area for the 80-terminal PFP PowerPAD

package is 10 mm

× 10 mm. The actual PowerPAD size for the TSB41BA3A is 6 mm × 6 mm.

It is required 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 thermal lands and thermal vias are detailed in the Texas Instruments PowerPAD



Thermally Enhanced Package application report (SLMA002) available via the Texas Instruments web pages

at URL: http://www.ti.com.

Figure 9. Example of a Thermal Land for the TSB41BA3A PHY

For the TSB41BA3A, 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

ought to 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 Texas Instruments application note PHY Layout (SLLA020).

PowerPAD is a trademark of Texas Instruments.

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