CALIFORNIA MICRO DEVICES

©2001 California Micro Devices Corp. All rights reserved. Smart OR™ is a trademark of California Micro Devices.

3/6/2001

215 Topaz Street, Milpitas, California 95035



Tel: (408) 263-3214

Fax: (408) 263-7846

www.calmicro.com

8

CMPWR330

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 CMPWR330 uses a thermally enhanced package

where all the GND pins (5 through 8) are integral to the

leadframe. When this package is mounted on a double

sided printed circuit board with two square inches of

copper allocated for “heat spreading”, the resulting

θ

50°C/W.

Based on a maximum power dissipation of 0.7W

(1.75V x 0.4A) with an ambient of 70°C the resulting

junction temperature will be:

T

= 70°C + 0.7W (50°C/W)

= 70°C + 35°C = 105°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

separate ground and power planes will further enhance

the overall thermal performance. 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 CMPWR330 with an

overall

θ

safely dissipated.

Figure 23. V

Figure 25. V

Figure 24. Select/DeselectThresholdVariation withT

JUNC

20

30

40

50

60

70

Temperature (

3.28

3.29

3.30

3.31

3.32

25

50

75

100

125

150

Temperature (

4.20

4.25

4.30

4.35

4.40

4.45

4.50

4.55

20

30

40

50

60

70

Temperature (

0.25

0.27

0.29

0.31

0.35

0.33

0.37