CM3102 Datasheet, PDF (8/9 Pages) California Micro Devices Corp – Micropower 1.2V/150mA CMOS LDO Regulator with Power Good

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,
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.
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.
CM3102
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
75
AMBIENT TEMPERATURE [^oC]
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 75 100 125
JUNCTION TEMPERATURE [^oC]
Short Circuit Current vs. T_JUNCT
200
150
100
50
0
-50
-25 0 25 50 75 100 125
JUNCTION TEMPERATURE [^oC]
© 2004 California Micro Devices Corp. All rights reserved.
8 430 N. McCarthy Blvd., Milpitas, CA 95035-5112 L Tel: [phone]
L Fax: [phone] L www.calmicro.com
01/20/04