MIC5239

Micrel

MIC5239

10

January 2002

0

100

200

300

400

500

600

700

800

900

0

0.25 0.50 0.75 1.00 1.25 1.50

POWER DISSIPATION (W)

85

°C

50

°C 25°C

T

J

= 125

°C

Figure 7. Copper Area vs. Power-MSOP

Power Dissipation (T

0

100

200

300

400

500

600

700

800

900

0

0.25 0.50 0.75 1.00 1.25 1.50

POWER DISSIPATION (W)

∆T

Figure 8. Copper Area vs. Power-SOIC

Power Dissipation (

∆∆∆∆∆T

0

100

200

300

400

500

600

700

800

900

0

0.25 0.50 0.75 1.00 1.25 1.50

POWER DISSIPATION (W)

85

°C

50

°C 25°C

T

J

= 125

°C

Figure 9. Copper Area vs. Power-SOIC

Power Dissipation (T

The same method of determining the heat sink area used for

the power-MSOP-8 can be applied directly to the power-

SOIC-8. The same two curves showing power dissipation

versus copper area are reproduced for the power-SOIC-8

and they can be applied identically.

Power SOIC-8 Thermal Characteristics

The power-SOIC-8 package follows the same idea as the

power-MSOP-8 package, using four ground leads with the

die attach paddle to create a single-piece electrical and

thermal conductor, reducing thermal resistance and increas-

ing power dissipation capability.

Quick Method

Determine the power dissipation requirements for the design

along with the maximum ambient temperature at which the

device will be operated. Refer to Figure 9, which shows safe

operating curves for three different ambient temperatures,

25

°C, 50°C, and 85°C. From these curves, the minimum

amount of copper can be determined by knowing the maxi-

mum power dissipation required. If the maximum ambient

temperature is 50

°C, and the power dissipation is 632mW,

the curve in Figure 9 shows that the required area of copper

Adjustable Regulator Application

MIC5239BM/MM

EN

GND

OUT

IN

2

41

3

5-8

V

R1

R2

1

µF

OUT

ADJ

Figure 10. Adjustable Voltage Application

The MIC5239BM can be adjusted from 1.24V to 20V by using

two external resistors (Figure 10). The resistors set the output

voltage based on the following equation:

V

R

R

1

2

)

Where V

Feeback resistor R2 should be no larger than 300k

Ω.