TLK3101_16 Datasheet, PDF (22/28 Pages) Texas Instruments – 2.5 Gbps to 3.125 Gbps TRANSCEIVER

TLK3101
2.5 Gbps to 3.125 Gbps TRANSCEIVER
SCAS649B − AUGUST 2000 − REVISED JANUARY 2008
designing with PowerPAD
The TLK3101 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 × 8 mm.
A thermal land, which is an area of solder-tinned-copper, is recommended underneath the PowerPAD package.
The thermal land will vary 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 16. Example of a Thermal Land
For the TLK3101, 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 pin landing pads be connected directly to the grounded thermal land. The land size
should be as large as possible without shorting device signal pins. 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.
22
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265