PRODUCT DATASHEET
AAT3221/2
PowerLinearTM
150mA NanoPower™ LDO Linear Regulator
The power dissipation for a 150mA load occurring for
8.2% of the duty cycle will be 20.9mW. Finally, the two
power dissipation levels can summed to determine the
total true power dissipation under the varied load:
Printed Circuit Board Layout
Recommendations
In order to obtain the maximum performance from the
AAT3221/2 LDO regulator, very careful attention must
be considered in regard to the printed circuit board lay-
out. If grounding connections are not properly made,
power supply ripple rejection and LDO regulator tran-
sient response can be compromised.
PD(total) = PD(100mA) + PD(150mA)
PD(total) = 229.5mW + 30.75mW
PD(total) = 260.25mW
The LDO regulator external capacitors CIN and COUT
should be connected as directly as possible to the ground
pin of the LDO regulator. For maximum performance
with the AAT3221/2, the ground pin connection should
then be made directly back to the ground or common of
the source power supply. If a direct ground return path
is not possible due to printed circuit board layout limita-
tions, the LDO ground pin should then be connected to
the common ground plane in the application layout.
The maximum power dissipation for the AAT3221/2
operating at an ambient temperature of 85°C is 267mW.
The device in this example will have a total power dis-
sipation of 260.25mW. This is within the thermal limits
for safe operation of the device.
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