CM3018 Datasheet, PDF (9/11 Pages) California Micro Devices Corp – Micropower, 150mA Low Noise CMOS Regulator with Fast Response

Performance Information (cont’d)
Typical Thermal Characteristics
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 resis-
tance 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)
SOT-23 Package Considerations
When the SOT23 version of the CM3018 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 320mW
(Load x V_IN-V_OUT = 150mA x 2.2V) with an ambient of
70°C the resulting junction temperature will be:
T_JUNC = T_AMB + P_D ∗ (θ_JA)
= 70°C + 315mW ∗ (175°C/W)
= 70°C + 57.75°C = 127.75°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 a 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 typically provide the CM3018 in a
SOT23 package with an overall θ_JA of 175°C/W, which
allows up to 450mW to be dissipated safely.
Please consult CAMD Technical Support for assistance
with thermal analysis of the CM3018 with respect to a
specific application.
PRELIMINARY
CM3018
Ground Current vs. Temperature
(VIN=5V)
100
80
60
40
20
0
0
25 50 75 100 125
TEMPERATURE [^oC]
Output Voltage Change vs. Temperature
(VIN=5V, 1mA Load)
50
40
30
20
10
0
-10
-20
-30
-40
-50
-50 -25 0 25 50 75 100 125
TEMPERATURE [^oC]
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