Datasheet

AD8150

Rev. A | Page 28 of 44

HEAT SINKING

Depending on several factors in its operation, the AD8150 can

dissipate 2 W or more. The part is designed to operate without

the need for an explicit external heat sink. However, the package

design offers enhanced heat removal via some of the package

pins to the PC board traces.

The V

pins on the input sides of the package (Pins 1 to 46 and

Pins 93 to 138) have finger extensions inside the package that

connect to the paddle on which the IC chip is mounted. These

pins provide a lower thermal resistance from the IC to the V

pins than pins that just have a bond wire. As a result, these pins

can be used to enhance the heat removal process from the IC to

the circuit board and ultimately to the ambient.

The V

pins described above should be connected to a large

area of circuit board trace material to take the most advantage

of their lower thermal resistance. If there is a large area available

on an inner layer that is at V

potential, then vias can be

provided from the package pin traces to this layer. There should

be no thermal-relief pattern when connecting the vias to the

inner layers for these V

pins. Additional vias in parallel and

close to the pin leads can provide an even lower thermal

resistive path. If possible to use, 2 oz. copper foil will provide

better heat removal than 1 oz.

The AD8150 package has a specified thermal impedance, θ

, of

30°C/W. This is the worst case still-air value that can be

expected when the circuit board does not significantly enhance

the heat removal from the package. By using the concept

described above or by using forced-air circulation, the thermal

impedance can be lowered.

For an extreme worst case analysis, the junction rise above the

ambient can be calculated assuming 2 W of power dissipation

and θ

of 30°C/W to yield a 60°C rise above the ambient. There

are many techniques described above that can mitigate this

situation. Most actual circuits will not result in such a high rise

of the junction temperature above the ambient.