MIC79050_05 Datasheet, PDF (12/14 Pages) Micrel Semiconductor – Simple Lithium-Ion Battery Charger

MIC79050
Micrel, Inc.
temperature is +40°C and the power dissipation is as above,
0.46W, the curve in Figure 10 shows that the required area
of copper is 50mm².
The θ_JA of this package is ideally 63°C/W, but it will vary
depending upon the availability of copper ground plane to
which it is attached.
900
TJ = 125°C
700
85°C
50°C 25°C
600
500
400
300
200
100
00 _{0.25 0.50 0.75 1.00 1.25 1.50}
POWER DISSIPATION (W)
Figure 10. Copper Area vs. Power-SOIC
Power Dissipation (T_A)
Power MSOP-8 Thermal Characteristics
The power-MSO-8 package follows the same idea as the
power-SO-8 package, using four ground leads with the die
attach paddle to create a single-piece electrical and thermal
conductor, reducing thermal resistance and increasing power
dissipation capability.
The same method of determining the heat sink area used
for the power-SOIC-8 can be applied directly to the power-
MSOP-8. The same two curves showing power dissipation
versus copper area are reproduced for the power-MSOP-8
and they can be applied identically.
Quick Method
Determine the power dissipation requirements for the design
along with the maximum ambient temperature at which the
device will be operated. Refer to Figure 12, which shows safe
operating curves for 3 different ambient temperatures, +25°C,
+50°C and +85°C. From these curves, the minimum amount
of copper can be determined by knowing the maximum power
dissipation required. If the maximum ambient temperature is
+25°C and the power dissipation is 1W, the curve in Figure
12v shows that the required area of copper is 500mm²,when
using the power MSOP-8
900
800
700
600
500
400
300
200
100
00
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 11. Copper Area vs. Power-MSOP
Power Dissipation (ΔT_JA)
900
800 ^{TJ = 125°C}
700
85°C 50°C 25°C
600
500
400
300
200
100
00 _{0.25 0.50 0.75 1.00 1.25 1.50}
POWER DISSIPATION (W)
Figure 12. Copper Area vs. Power-MSOP
Power Dissipation (T_A)
MIC79050
12
August 2005