IRU1502-33 Datasheet, PDF (9/11 Pages) International Rectifier – MICROPOWER 1A LOW DROPOUT PMOS VOLTAGE REGULATOR

IRU1502-33
The thermal pad of MLPM is connected to a 1 inch square
copper through vias for a four layer PCB board design.
From the datasheet, this thermal junction-to-ambient re-
sistance is given as:
ΘJA=428C / W
Where:
ΘJC ≅ 2.38C
ΘCH ≅ 18C
ΘHA ≅ 38.78C
Layout Consideration
The IRU1502-33, like many other high-speed regulators,
requires that the output capacitors be close to the de-
vice for stability. For power consideration, a ground plane
pad of approximately one-inch square on the compo-
nent side must be dedicated to the device where all
ground pins are connected to dissipate the power. If a
multilayer board is used, it is recommended that the
inner layers of the board are also dedicated to the size
of the pad for better thermal characteristics.
For IRU1502-33, the thermal design needs to be con-
sider so that the resultant junction temperature is lower
than the maximum operating temperature, which is 1258C.
Therefore:
TJ = ΘJA3PD+TA [ 1258C
Assuming, the following conditions:
VOUT = 3.3V
VIN = 5V
IOUT = 1A (DC Avg)
Calculate the maximum power dissipation using the fol-
lowing equation:
PD = IOUT3(VIN - VOUT)
PD = 13(5 - 3.3) = 1.7W
For MLPM package, we have:
uJA = 428C/W
TA = 458C
DT = PD3uJA = 1.7342 = 71.4
TJ = TA+DT = 116.48C
Rev. 1.0
07/17/03
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Data and specifications subject to change without notice. 02/01
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