CM3004 Datasheet, PDF (7/9 Pages) California Micro Devices Corp – 1.0 Amp Dual Mode Low-Dropout CMOS Regulator

Performance Information (cont’d)
CM3004 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 lay-
out. 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 CM3004 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_JA
is about 50°C/W.
Based on a typical operating power dissipation of 1.0W
with an ambient of 85°C, the resulting junction temper-
ature will be:
T_JUNC = T_AMB + P_D (θ_JA)
= 85°C + 1.0W (50°C/W)
= 85°C + 50°C = 135°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". Mea-
surement was performed under light load conditions
(5mA).
PRELIMINARY
CM3004
Tem perature vs. Output Voltage (1.2V)
1.25
1.23
1.21
1.19
1.17
1.15
-40
25
85
Tem perature ('C)
Temperature vs. Output Voltage ( 2.5V )
2.60
2.55
2.50
2.45
2.40
-40 -25 0
25 50 75 85 100 125 150
Tem perature ('C)
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