CFXYY datasheet(13/16 Pages) ANALOGICTECH

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AAT3221/2

150mA NanoPower™ LDO Linear Regulator

PowerLinearTM

PRODUCT DATASHEET

3221.2007.11.1.12

www .analogictech.com

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:

PD(total) = PD(100mA) + PD(150mA)

PD(total) = 229.5mW + 30.75mW

PD(total) = 260.25mW

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.

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.

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.

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