TLK2501

1.5 TO 2.5 GBPS TRANSCEIVER

SLLS427D − AUGUST 2000 − REVISED JULY 2003

23

POST OFFICE BOX 655303

APPLICATION INFORMATION

designing with PowerPAD

The TLK2501 is housed in a high-performance, thermally enhanced, 64-pin VQFP (RCP64) 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 to connection

etches or vias under the package. It is strongly recommended that the PowerPAD be soldered to the thermal

land. The recommended convention, 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 minimum size required for the keep-out area for the 64-pin 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 thermal lands and thermal vias are detailed in the TI application note PowerPAD

Thermally Enhanced Package Application Report, TI literature number SLMA002, available via the TI Web

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

Figure 17. Example of a Thermal Land

For the TLK2501, this thermal land should 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

should 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.