REG104 datasheet(11/22 Pages) TI

11 / 22 page

REG104

SBVS025G

FIGURE 9. Maximum Power Dissipation versus Ambient

Temperature for the Various Packages and

PCB Heat Sink Configurations.

POWER DISSIPATION

The REG104 is available in two different package configura-

tions. The ability to remove heat from the die is different for

each package type and, therefore, presents different consid-

erations in the printed circuit board (PCB) layout. The PCB

area around the device that is free of other components

moves the heat from the device to the ambient air. While it

is difficult to impossible to quantify all of the variables in a

thermal design of this type, performance data for several

configurations are shown in Figure 9. In all cases the PCB

copper area is bare copper, free of solder resist mask, and

not solder plated. All examples are for 1-ounce copper. Using

heavier copper will increase the effectiveness in moving the

heat from the device. In those examples where there is

copper on both sides of the PCB, no connection has been

provided between the two sides. The addition of plated

through holes will improve the heat sink effectiveness.

Power dissipation depends on input voltage and load condi-

tions. Power dissipation is equal to the product of the aver-

age output current times the voltage across the output

element, VIN to VOUT voltage drop.

DIN

OUT

OUT AVG

=•

(

–

)

()

Power dissipation can be minimized by using the lowest

possible input voltage necessary to assure the required

output voltage.

125

100

Ambient Temperature (

°C)

CONDITIONS

CONDITION

PACKAGE

PCB AREA

DDPAK

4in2 Top Side Only

°C/W

SOT-223

4in2 Top Side Only

°C/W

DDPAK

None

°C/W

SOT-223

0.5in2 Top Side Only

110

°C/W

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