SLK2721

OC48+FEC/24/12/3 SONET/SDH MULTIRATE TRANSCEIVER

WITH ENHANCED JITTER TOLERANCE

SLLS532 − JUNE 2002

18

POST OFFICE BOX 655303

APPLICATION INFORMATION

designing with the PowerPad package

The SLK2721 device is housed in high-performance, thermally enhanced, 100-pin PZP PowerPAD packages.

Use of a 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. Correct

device operation requires that the PowerPAD be soldered to the thermal land. Do not run any etches or signal

vias under the device, but 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 100-pin PZP PowerPAD

package is 12 mm

× 12 mm.

A thermal land, which is an area of solder-tinned-copper, is required 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

Figure 11. Example of a Thermal Land

For the SLK2721 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 of the device. More

information may be obtained from the TI application note PHY Layout, TI literature number SLLA020.