MIC5209 Datasheet, PDF (10/13 Pages) Micrel Semiconductor – 500mA Low-Noise LDO Regulator

MIC5209
the MIC5209 is calculated using the voltage drop across the
device × output current plus supply voltage × ground current.
Considering worst case tolerances, the power dissipation
could be as high as:
(V_IN(max) – V_OUT(max)) × I_OUT + V_IN(max) × I_GND
[(3.6V – 2.375V) × 320mA] + (3.6V × 4mA)
P_D = 407mW
Using the maximum junction temperature of 125°C and a θ_JC
of 8°C/W for the SOT-223, 25°C/W for the SO-8, or 2°C/W for
the TO-263 package, the following worst-case heat-sink
thermal resistance (θ_SA) requirements are:
θ_JA =
T_J(max) − T_A
P_D
θ_SA = θ_JA − θ_JC
T_A
40°C
50°C
60°C
75°C
θ_JA (limit)
209°C/W 184°C/W 160°C/W 123°C/W
θ_SA SOT-223 201°C/W 176°C/W 152°C/W 115°C/W
θ_SA SO-8
184°C/W 159°C/W 135°C/W 98°C/W
θ_SA TO-263-5 207°C/W 182°C/W 158°C/W 121°C/W
Table 2. Maximum Allowable Thermal Resistance
Micrel
Table 2 and Figure 6 show that the Slot-1 power supply
application can be implemented with a minimum footprint
layout. Figure 6 shows the necessary copper pad area to
obtain specific
θ_SA values in
heat sink thermal resistance
Table 2 require much less
(θ_SA)
than
values. The
500mm² of
copper, according to Figure 6, and can easily be accom-
plished with the minimum footprint.
70
60
50
40
30
20
10
0
0
2000
4000
6000
COPPER HEAT SINK AREA (mm²)
Figure 6. PCB Heat Sink Thermal Resistance
MIC5209
10
August 2, 2000