THS3201D datasheet(20/29 Pages) TI

20 / 29 page

THS3201

SLOS416A − JUNE 2003 − REVISED JANUARY 2004

www.ti.com

PowerPAD PCB LAYOUT CONSIDERATIONS

Prepare the PCB with a top side etch pattern as shown

in Figure 62. There should be etch for the leads as well

as etch for the thermal pad.

Place five holes in the area of the thermal pad. These

holes should be 10 mils in diameter. Keep them small

so that solder wicking through the holes is not a

problem during reflow.

Additional vias may be placed anywhere along the

thermal plane outside of the thermal pad area. This

helps dissipate the heat generated by the THS3201

IC. These additional vias may be larger than the 10-mil

diameter vias directly under the thermal pad. They can

be larger because they are not in the thermal pad area

to be soldered so that wicking is not a problem.

Connect all holes to the internal ground plane.

When connecting these holes to the ground plane, do

not use the typical web or spoke via connection

methodology. Web connections have a high thermal

resistance connection that is useful for slowing the

heat transfer during soldering operations. This makes

the soldering of vias that have plane connections

easier. In this application, however, low thermal

resistance is desired for the most efficient heat

transfer. Therefore, the holes under the THS3201

PowerPAD package should make their connection to

the internal ground plane with a complete connection

around the entire circumference of the plated-through

hole.

The top-side solder mask should leave the terminals

of the package and the thermal pad area with its five

holes exposed. The bottom-side solder mask should

cover the five holes of the thermal pad area. This

prevents solder from being pulled away from the

thermal pad area during the reflow process.

Apply solder paste to the exposed thermal pad area

and all of the IC terminals.

With these preparatory steps in place, the IC is simply

placed in position and run through the solder reflow

operation

any

standard

surface-mount

component. This results in a part that is properly

installed.

POWER DISSIPATION AND THERMAL

CONSIDERATIONS

To maintain maximum output capabilities, the THS3201

does not incorporate automatic thermal shutoff protection.

The designer must take care to ensure that the design

does not violate the absolute maximum junction

temperature of the device. Failure may result if the

absolute maximum junction temperature of 150

°C is

exceeded. For best performance, design for a maximum

junction temperature of 125

°C. Between 125°C and

150

°C, damage does not occur, but the performance of the

amplifier begins to degrade.

The thermal characteristics of the device are dictated by

the package and the PC board. Maximum power

dissipation for a given package can be calculated using the

following formula.

Dmax +

Tmax

* T

where:

PDmax is the maximum power dissipation in the

amplifier (W).

Tmax is the absolute maximum junction

temperature (

°C).

TA is the ambient temperature (°C).

θJA = θJC + θCA

θJC is the thermal coefficient from the silicon

junctions to the case (

°C/W).

θCA is the thermal coefficient from the case to

ambient air (

°C/W).

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