P

D

I

OUT

R

q

JA

+

P

D

160

140

120

100

80

60

40

20

0

0

1

2

3

4

5

6

7

8

9

10

Board Copper Area (

)

in

2

DCQ

DRB

TPS796xx-Q1

www.ti.com

SBVS154 – MARCH 2012

THERMAL INFORMATION

POWER DISSIPATION

Knowing the device power dissipation and proper sizing of the thermal plane that is connected to the tab or pad

is critical to avoiding thermal shutdown and ensuring reliable operation.

Power dissipation of the device depends on input voltage and load conditions and can be calculated using

Equation 1:

(1)

Power dissipation can be minimized and greater efficiency can be achieved by using the lowest possible input

voltage necessary to achieve the required output voltage regulation.

On the SON (DRB) package, the primary conduction path for heat is through the exposed pad to the PCB. The

pad can be connected to ground or be left floating; however, it should be attached to an appropriate amount of

copper PCB area to ensure the device does not overheat. On the SOT-223 (DCQ) package, the primary

conduction path for heat is through the tab to the PCB. That tab should be connected to ground. The maximum

junction-to-ambient thermal resistance depends on the maximum ambient temperature, maximum device junction

temperature, and power dissipation of the device and can be calculated using Equation 2:

(2)

be estimated using Figure 22.

Note:

Figure 22.

Figure 22 shows the variation of

a guideline to demonstrate the effects of heat spreading in the ground plane and should not be used to estimate

actual thermal performance in real application environments.

NOTE: When the device is mounted on an application PCB, it is strongly recommended to use

explained in the Estimating Junction Temperature section.

Copyright © 2012, Texas Instruments Incorporated

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