THS4021, THS4022

350-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS

SLOS265B – SEPTEMBER 1999 – REVISED FEBRUARY 2000

16

POST OFFICE BOX 655303

APPLICATION INFORMATION

general PowerPAD design considerations (continued)

The actual thermal performance achieved with the THS402xDGN in its PowerPAD package depends on the

application. In the example above, if the size of the internal ground plane is approximately 3 inches

× 3 inches,

then the expected thermal coefficient,

the THS402x IC (SOIC) is shown. For a given

is calculated by the following formula:

P

D +

T

MAX

–T

A

q

JA

Where:

= Maximum power dissipation of THS402x IC (watts)

= Free-ambient air temperature (

°C)

DGN Package

θJA = 58.4°C/W

2 oz. Trace And Copper Pad

With Solder

DGN Package

θJA = 158°C/W

2 oz. Trace And

Copper Pad

Without Solder

SOIC Package

High-K Test PCB

θJA = 98°C/W

TJ = 150°C

SOIC Package

Low-K Test PCB

θJA = 167°C/W

2

1.5

1

0

–40

–20

0

20

40

2.5

3

MAXIMUM POWER DISSIPATION

vs

FREE-AIR TEMPERATURE

3.5

60

80

100

0.5

TA – Free-Air Temperature – °C

NOTE A: Results are with no air flow and PCB size = 3”

× 3”

Figure 39. Maximum Power Dissipation vs Free-Air Temperature

More complete details of the PowerPAD installation process and thermal management techniques can be found

in the Texas Instruments Technical Brief,

PowerPAD Thermally Enhanced Package. This document can be

found at the TI web site (www.ti.com) by searching on the key word PowerPAD. The document can also be

ordered through your local TI sales office. Refer to literature number SLMA002 when ordering.