The THS309x are available in a thermally-enhanced PowerPAD family of packages. These packages are constructed using a downset leadframe on which the die is mounted [see Figure 9-6(a) and Figure 9-6(b)]. This arrangement results in the lead frame being exposed as a thermal pad on the underside of the package [see Figure 9-6(c)]. Because this thermal pad has direct thermal contact with the die, excellent thermal performance can be achieved by providing a good thermal path away from the thermal pad. Note that devices such as the THS309x have no electrical connection between the PowerPAD and the die.

The PowerPAD package allows for both assembly and thermal management in one manufacturing operation. During the surface-mount solder operation (when the leads are being soldered), the thermal pad can also be soldered to a copper area underneath the package. Through the use of thermal paths within this copper area, heat can be conducted away from the package into either a ground plane or other heat-dissipating device.

The PowerPAD package represents a breakthrough in combining the small area and ease of assembly of surface mount with the awkward mechanical methods of heatsinking.

Figure 9-6 Views of Thermal Enhanced Package

Although there are many ways to properly heatsink the PowerPAD package, the following section lists the recommended steps.