CM3102
Performance Information (cont’d)
CM3102-12ST/SO Typical Thermal Characteristics
The overall junction to ambient thermal resistance
(
θ
JA
) for device power dissipation (PD) consists prima-
rily of two paths in series. The first path is the junction
to the case (
θ
JC
) which is defined by the package style,
OUTPUT VOLTAGE
[V]
V
OUT
Variation with T
AMB
(150mA Load)
1.230
1.220
1.210
1.200
1.190
1.180
1.170
-25
0
25
50
AMBIENT TEMPERATURE [
o
C]
75
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 con-
ditions can be estimated by the following thermal equa-
tion:
T
JUNC
= T
AMB
+ P
D
(
θ
JC
) + P
D
(
θ
CA
)
= T
AMB
+ P
D
(
θ
JA
)
The CM3102-12ST/SO uses a SOT23-5 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
θ
JA
is
175°C/W.
OUTPUT VOLTAGE
[V]
V
OUT
Variation with T
JUNCT
(1mA Load)
1.230
1.220
1.210
1.200
1.190
1.180
1.170
-25
0
25
50
75
100
JUNCTION TEMPERATURE [
o
C]
125
Based on a maximum power dissipation of 315mW
(2.1Vx150mA), with an ambient of 70°C the resulting
junction temperature will be:
T
JUNC
= T
AMB
+ P
D
(
θ
JA
)
= 70°C + 315mW X (175°C/W)
= 70°C + 55°C = 125°C
Thermal characteristics were measured using a double
sided board with two square inches of copper area
connected to the GND pin for "heat spreading".
Measurements showing performance up to junction
temperature of 125°C were performed under light load
conditions (1mA). This allows the ambient temperature
to be representative of the internal junction tempera-
ture.
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 provide the CM3102-12ST/SO with
an overall
θ
JA
of 175°C/W which allows up to 450mW
to be safely dissipated for the maximum junction tem-
perature.
Short Circuit Current vs. T
JUNCT
200
SHORT CIRCUIT CURRENT [mA]
150
100
50
0
-50
-25
0
25
50
75
o
100
125
JUNCTION TEMPERATURE [ C]
© 2004 California Micro Devices Corp. All rights reserved.
8
430 N. McCarthy Blvd., Milpitas, CA 95035-5112
L
Tel: 408.263.3214
L
Fax: 408.263.7846
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www.calmicro.com
01/20/04
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
