July 2005

11

MIC5236

MIC5236

Micrel, Inc.

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 as above,

632mW, the curve in Figure 7 shows that the required area

depending upon the availability of copper ground plane to

which it is attached.

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

TJ = 125°C

Figure 7. Copper Area vs. Power-SOIC

0

100

200

300

400

500

600

700

0 0.25 0.50 0.75 1.00 1.25 1.50

POWER DISSIPATION (W)

Figure 8. Copper Area vs. Power-MSOP

The same method of determining the heat sink area used

for the power-SOIC-8 can be applied directly to the power-

MSOP-8. The same two curves showing power dissipation

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

and they can be applied identically, see Figures 8 and 9.

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

TJ = 125°C

Figure 9. Copper Area vs. Power-MSOP

Power MSOP-8 Thermal Characteristics

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

power-SO-8 package, using four ground leads with the die

attach paddle to create a single-piece electrical and thermal

conductor, reducing thermal resistance and increasing 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 639mW,

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

Adjustable Regulator Application

MIC5236BM/MM

EN

GND

OUT

IN

2

4

1

3

5-8

V

R1

R2

1µF

OUT

ADJ

Figure 10. Adjustable Voltage Application

The MIC5236BM/MM 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:

R

R

1