THS3115IPWPRG4 datasheet(17/35 Pages) TI1

17 / 35 page

0.205

(5,21)

0.060

(1,52)

0.013

(0,33)

0.017

(0,432)

0.025

(0,64)

0.094

(2,39)

0.040

(1,01)

0.035

(0,89)

0.075

(1,91)

0.010

vias

(0,254)

0.030

(0,76)

Pin1

TopView

DMax

max

THS3112

THS3115

www.ti.com

SLOS385C – SEPTEMBER 2001 – REVISED SEPTEMBER 2010

PowerPAD™ Layout Considerations

transfer.

Therefore,

the

holes

under

the

THS3115/THS3112 PowerPAD package should

make the connection 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

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 configuration prevents

solder from being pulled away from the thermal

pad area during the reflow process.

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

solder

reflow

operation

any

standard

surface-mount component. This procedure results

Dimensions are in inches (millimeters).

in a part that is properly installed.

Figure 51. DGN PowerPAD PCB Etch and Via

Power Dissipation and Thermal

Pattern

Considerations

Although there are many ways to properly heatsink

The THS3115 and THS3112 incorporate automatic

the PowerPAD package, the following steps illustrate

thermal shutoff protection. This protection circuitry

the recommended approach.

shuts down the amplifier if the junction temperature

exceeds approximately +160°C. When the junction

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

temperature reduces to approximately +140°C, the

Figure 51.

amplifier turns on again. However, for maximum

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

performance and reliability, the designer must take

These holes should be 0.01 inch (0,254 mm) in

care to ensure that the design does not exceed a

diameter. Keep them small so that solder wicking

junction temperature of +125°C. Between +125°C

through the holes is not a problem during reflow.

and +150°C, damage does not occur, but the

3. Additional vias may be placed anywhere along

performance of the amplifier begins to degrade and

the thermal plane outside of the thermal pad

long-term

reliability

suffers.

The

thermal

area.

These

vias

help

dissipate

the

heat

characteristics of the device are dictated by the

generated by the THS3115/THS3112 IC. These

package and the PCB. Maximum power dissipation

additional vias may be larger than the 0.01-inch

for a given package can be calculated using the

(0,254-mm) diameter vias directly under the

following formula.

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.

4. Connect all holes to the internal ground plane.

where:

Note that the PowerPAD is electrically isolated

•

PDMax is the maximum power dissipation in the

from the silicon and all leads. Connecting the

amplifier (W)

PowerPAD to any potential voltage, such as VS–,

•

Tmax is the absolute maximum junction

is acceptable as there is no electrical connection

temperature (°C)

to the silicon.

•

TA is the ambient temperature (°C)

5. When connecting these holes to the ground

qJA = qJC + qCA

plane, do not use the typical web or spoke via

connection methodology. Web connections have

where:

a high thermal resistance connection that is

•

qJC is the thermal coefficient from the silicon

useful for slowing the heat transfer during

junctions to the case (°C/W)

soldering operations. This resistance makes the

•

qCA is the thermal coefficient from the case to

soldering of vias that have plane connections

ambient air (°C/W)

easier. In this application; however, low thermal

resistance is desired for the most efficient heat

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