CALIFORNIA MICRO DEVICES

©2001 California Micro Devices Corp. All rights reserved. SmartOR™ is a trademark of California Micro Devices Corporation.

3/6/2001

215 Topaz Street, Milpitas, California 95035



Tel: (408) 263-3214

Fax: (408) 263-7846

www.calmicro.com

6

CMPWR101

Typical Thermal Characteristics

The overall junction to ambient thermal resistance (

θ

for device power dissipation (P

two paths in series. The first path is the junction to the

case (

θ

second path is case to ambient (

θ

which is dependent on board layout. The final operating

junction temperature for any set of conditions can be

estimated by the following thermal equation:

T

= T

The CMPWR101 uses a standard SOIC package. When

this package is mounted on a double sided printed

circuit board with two square inches of copper allocated

for “heat spreading”, the resulting overall

θ

Based on maximum power dissipation of 0.43W

(1.7V x 250mA) with an ambient of 70°C the resulting

junction temperature will be:

T

= 70°C + 0.43W (80°C/W)

= 70°C + 37°C

= 103°C

Thermal characteristics were measured using a double

sided board with two square inches of copper area

connected to the GND pins for “heat spreading”.

Measurements showing performance up to junction

temperature of 125°C were performed under light load

conditions (5mA). This allows the ambient temperature

to be representative of the internal junction temperature.

Note: The use of multi-layer board construction with

power planes will further enhance the thermal perfor-

mance of the package. In the event of no copper area

being dedicated for heat spreading, a multi-layer board

construction, using only the minimum size pad layout,

will typically provide the CMPWR101 with an overall

θ

JA

of 100°C/W, which allows up to 0.5W to be safely

dissipated.

3.284

3.286

3.288

3.290

3.292

3.294

3.296

3.298

3.300

20

30

40

50

60

70

Figure 13. Regulator V

4.08

4.10

4.12

4.14

4.16

4.18

25

50

75

100

125

Figure 14. Deselect Threshold vs T

JUNCT

0.20

0,22

0.24

0.26

0.28

0.30

0.32

0.34

0.36

20

30

40

50

60

70

Ambient Temperature (

Figure 15. Switch Resistance vs AmbientTemperature