TAS5110

SLES028A – MAY 2002 – REVISED SEPTEMBER 2002

15

www.ti.com

Thermal Methodology for the 32-Pin DAD Package 50 W, 6-

Ω Test

The thermal test for the DAD part (e.g., thermal pad oriented away from the board) was conducted as shown

in Figure 7 and Figure 8. The cooling approach was to attach a heat sink to the thermal pad and conduct the

heat to ambient air.

Since the approach was to use a chassis below the board, it was inverted and a spacer bar used to connect

the pads thermally to the heat sink. The bar was made high enough that the components on the board were

clear of the chassis.

The pad-to-spacer thermal resistance was about 3.2

_C/W with the thermal compound indicated.

The chassis provided the only heat sink to air and was chosen as representative of a possible cooling approach.

A closed plastic top and insulating front and back panels ensured that only the bottom and sides of the U shaped

chassis contributed to cooling. The chassis was spaced 0.25 inch from the table to simulate a normal chassis

configuration. The thermal pad does not need to be isolated from ground. (Any heat sink with a thermal

resistance to air of 3.9

_C/W or lower also works.) In this test, the exposed chassis reached long-term equilibrium

temperatures above 50

_C, so the approach would have to be modified for touch temperature consideration. The

chassis temperature after 10 minutes of 50 W into 6

Ω was below 50_C.

The test ran for three hours with 2 x 50 W RMS at 1 kHz into a 6-

Ω resistive load at an ambient lab temperature

of 23

_C. No audio or thermal problems were encountered during that time.

32 DAD Package

Wakefield Type 126

Thermal Compound

(3.2

°C/W)

Aluminum Space Bar

(1/4 in Thick)

(2.44

°C/W)

Stereo Amplifier

Board

Wakefield Type 126

Thermal Compound

(0.169

°C/W)

1.25 in

Aluminum Chassis 7.2 in x 1 in x 0.1 in Thick

Sides of U-Shaped Chassis Are 1.25 in High

(3.9

°C/W)

Insulating

Back Panel

Insulating

Front Panel

Plastic Top Cover

Figure 7. 32-Pin DAD Package Cross-Sectional View (Side)