CALIFORNIA MICRO DEVICES
Typical Thermal Characteristics
Full Load Output Voltage (V)
CMPWR101
3.300
3.298
3.296
3.294
3.292
3.290
3.288
3.286
3.284
20
30
40
50
60
70
The overall junction to ambient thermal resistance (θ
JA
)
for device power dissipation (P
D
) consists primarily of
two paths in series. The first path is the junction to the
case (θ
JC
) which is defined by the package style, and the
second path is case to ambient (θ
CA
) thermal resistance
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
JUNC
= T
AMB
+ P
D
(θ
JC
) + P
D
(θ
CA
)
= T
AMB
+ P
D
(θ
JA
)
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
JA
is 85°C/W.
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
JUNC
= T
AMB
+ P
D
(θ
JA
)
= 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.
Ambient Temperature (
˚
C)
Figure 13. Regulator V
OUT
vs T
AMB
(250mA Load)
4.18
Deselect Voltage Level (V)
4.16
4.14
4.12
4.10
4.08
25
50
75
100
125
Junction Temperature (
˚
C)
Figure 14. Deselect Threshold vs T
JUNCT
0.36
0.34
0.32
Resistance (Ω)
0.30
0.28
0.26
0.24
0,22
0.20
20
30
40
50
60
70
Ambient Temperature (
˚
C)
Figure 15. Switch Resistance vs Ambient Temperature
©2001 California Micro Devices Corp. All rights reserved. SmartOR™ is a trademark of California Micro Devices Corporation.
6
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
3/6/2001
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
