AAT1143 데이터 시트보기 (PDF) - Analog Technology Inc

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AAT1143

1MHz 400mA Step-Down Converter

Analog Technology Inc 

AAT1143

1MHz 400mA Step-Down Converter

Figure 2: AAT1143 Evaluation Board

Top Side.

Figure 3: Exploded View of Evaluation

Board Top Side Layout.

Figure 4: AAT1143 Evaluation Board

Bottom Side.

The maximum output capacitor RMS ripple current

is given by:

I = RMS(MAX)

1

2·

·

3

VOUT · (VIN(MAX) - VOUT)

L · F · VIN(MAX)

Dissipation due to the RMS current in the ceramic

output capacitor ESR is typically minimal, resulting in

less than a few degrees rise in hot-spot temperature.

Adjustable Output Resistor Selection

For applications requiring an adjustable output volt-

age, the 0.6V version can be externally pro-

grammed. Resistors R1 and R2 of Figure 5 program

the output to regulate at a voltage higher than 0.6V.

To limit the bias current required for the external

feedback resistor string while maintaining good

noise immunity, the minimum suggested value for

R2 is 59kΩ. Although a larger value will further

reduce quiescent current, it will also increase the

impedance of the feedback node, making it more

sensitive to external noise and interference. Table 2

summarizes the resistor values for various output

voltages with R2 set to either 59kΩ for good noise

immunity or 221kΩ for reduced no load input current.

R1

=

⎛ VOUT

⎝ VREF

-1⎞⎠

·

R2

=

⎛ 1.5V

⎝ 0.6V

-

1 ⎞⎠

·

59kΩ

=

88.5kΩ

12

1143.2005.09.1.7

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