IRU1150 Ver la hoja de datos (PDF) - International Rectifier
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IRU1150 Datasheet PDF : 9 Pages
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IRU1150(PbF)
Stability
The IRU1150 requires the use of an output capacitor as
part of the frequency compensation in order to make the
regulator stable. Typical designs for the microprocessor
applications use standard electrolytic capacitors with
typical ESR in the range of 50 to 100mς and an output
capacitance of 500 to 1000µF. Fortunately as the ca-
pacitance increases, the ESR decreases resulting in a
fixed RC time constant. The IRU1150 takes advantage
of this phenomena in making the overall regulator loop
stable.
For most applications a minimum of 100µF aluminum
electrolytic capacitor such as Sanyo, MVGX series,
Panasonic FA series as well as the Nichicon PL series
insures both stability and good transient response.
Assuming, the following conditions:
VOUT = 2.7V
VIN = 3.3V
VCTRL = 5V
IOUT = 2A (DC Avg)
Calculate the maximum power dissipation using the fol-
lowing equation:
( ) PD = IOUT3(VIN - VOUT)+
IOUT
60
3(VCTRL - VOUT)
( ) PD = 23(3.3 - 2.7)+
2
60
3(5 - 2.7) = 1.28W
Using table below select the proper package and the
amount of copper board needed.
Thermal Design
The IRU1150 incorporates an internal thermal shutdown
that protects the device when the junction temperature
exceeds the allowable maximum junction temperature.
Although this device can operate with junction tempera-
tures in the range of 1508C, it is recommended that the
selected heat sink be chosen such that during maxi-
mum continuous load operation the junction tempera-
ture is kept below this number. The example below
shows the steps in selecting the proper surface mount
package.
Pkg Copper θJA(°C/W)
Area
TO-263 1.4"X1.4" 25
TO-263 1.0"X1.0" 30
TO-263 0.7"X0.7" 35
TO-263 Pad Size 45
SO-8 1.0"X1.0" 55
Max Pd
(TA=25°C)
4.4W
3.7W
3.1W
2.4W
2.0W
Max Pd
(TA=45°C)
3.6W
3.0W
2.6W
2.0W
1.63W
Note: Above table is based on the maximum junction
temperature of 1358C.
As shown in the above table, any of the two packages
will do the job. For low cost applications the SOIC 8-pin
package is recommended.
Rev. 1.8
www.irf.com
5
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