THS3111 datasheet(21/28 Pages) TI

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0.060

0.040

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vias

Pin 1

Top View

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PowerPAD™ LAYOUT CONSIDERATIONS

POWER DISSIPATION AND THERMAL

THS3110, THS3111

SLOS422A – SEPTEMBER 2003 – REVISED NOVEMBER 2003

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. There-

fore, the holes under the THS3110 / THS3111

PowerPAD package should make their connec-

tion to the internal ground plane with a complete

connection around the entire circumference of the

plated-through hole.

6. The top-side solder mask should leave the ter-

minals 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

Figure 56. DGN PowerPAD PCB Etch and Via

during the reflow process.

Pattern

7. Apply solder paste to the exposed thermal pad

area and all of the IC terminals.

8. With these preparatory steps in place, the IC is

simply placed in position and run through the

1. PCB with a top side etch pattern as shown in

solder reflow operation as any standard sur-

Figure 56. There should be etch for the leads as

face-mount component. This results in a part that

well as etch for the thermal pad.

is properly installed.

2. 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

CONSIDERATIONS

holes is not a problem during reflow.

The THS3110 and THS3111 incorporates automatic

3. Additional vias may be placed anywhere along

thermal shutoff protection. This protection circuitry

the thermal plane outside of the thermal pad

shuts down the amplifier if the junction temperature

area. This helps dissipate the heat generated by

exceeds approximately 160

°C. When the junction

the THS3110 / THS3111 IC. These additional

temperature reduces to approximately 140

°C, the

vias may be larger than the 10-mil diameter vias

amplifier turns on again. But, for maximum perform-

directly under the thermal pad. They can be

ance and reliability, the designer must take care to

larger because they are not in the thermal pad

ensure that the design does not exeed a junction

area to be soldered so that wicking is not a

temperature of 125

°C. Between 125°C and 150°C,

problem.

damage does not occur, but the performance of the

4. Connect all holes to the internal ground plane.

amplifier begins to degrade and long term reliability

Note that the PowerPAD is electrically isolated

suffers. The thermal characteristics of the device are

from the silicon and all leads. Connecting the

dictated by the package and the PC board. Maximum

PowerPAD to any potential voltage such as VS-,

power dissipation for a given package can be calcu-

is acceptable as there is no electrical connection

lated using the following formula.

to the silicon.

5. When connecting these holes to the ground

plane, do not use the typical web or spoke via

connection methodology. Web connections have

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