MIC5239 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – Low Quiescent Current 500mA UCap LDO Regulator

MIC5239
900
800 ^{TJ = 125°C}
700
85°C 50°C 25°C
600
500
400
300
200
100
0
0 0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 7. Copper Area vs. Power-MSOP
Power Dissipation (T_A)
900
800
700 ^{∆TJA =}
600
500
400
300
200
100
0
0 0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 8. Copper Area vs. Power-SOIC
Power Dissipation (∆T_JA)
900
800 ^{TJ = 125°C}
700
85°C
600
50°C 25°C
500
400
300
200
100
0
0 0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 9. Copper Area vs. Power-SOIC
Power Dissipation (T_A)
The same method of determining the heat sink area used for
the power-MSOP-8 can be applied directly to the power-
SOIC-8. The same two curves showing power dissipation
versus copper area are reproduced for the power-SOIC-8
and they can be applied identically.
Micrel
Power SOIC-8 Thermal Characteristics
The power-SOIC-8 package follows the same idea as the
power-MSOP-8 package, using four ground leads with the
die attach paddle to create a single-piece electrical and
thermal conductor, reducing thermal resistance and increas-
ing power dissipation capability.
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 9, which shows safe
operating curves for three different ambient temperatures,
25°C, 50°C, and 85°C. From these curves, the minimum
amount of copper can be determined by knowing the maxi-
mum power dissipation required. If the maximum ambient
temperature is 50°C, and the power dissipation is 632mW,
the curve in Figure 9 shows that the required area of copper
is less than 100mm²,when using the power SOIC-8.
Adjustable Regulator Application
MIC5239BM/MM
2
3
V_IN
IN OUT
V_OUT
4
1 ^R1
EN ADJ
1µF
GND
R2
5-8
Figure 10. Adjustable Voltage Application
The MIC5239BM can be adjusted from 1.24V to 20V by using
two external resistors (Figure 10). The resistors set the output
voltage based on the following equation:
R1
V_OUT = V_REF (1 + _R2 )
Where V_REF = 1.23V.
Feeback resistor R2 should be no larger than 300kΩ.
MIC5239
10
January 2002