The OPA561 uses the HTSSOP-20 PowerPAD integrated circuit package, a thermally enhanced, standard-size IC package designed to eliminate the use of bulky heat sinks and slugs traditionally used in thermal packages. This package can be easily mounted using standard PCB assembly techniques, and can be removed and replaced using standard repair procedures.

The PowerPAD package is designed so that the leadframe die pad (or thermal pad) is exposed on the bottom of the IC, as shown in Figure 7-4. This provides an extremely low thermal resistance (θ_JC) path between the die and the exterior of the package. The thermal pad on the bottom of the IC must be soldered directly to the PCB, using the PCB as a heat sink. In addition, through the use of thermal vias, the thermal pad can be directly connected to a ground plane or special heat sink structure designed into the PCB.

Figure 7-4 Section View of a PowerPAD Package

Soldering the thermal pad to the PCB is always recommended, even with applications that have low power dissipation. Soldering provides the necessary connection between the leadframe die and the PCB. Connect the thermal pad to the most negative supply of the device.