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AAT1143 Datasheet, PDF (12/20 Pages) Advanced Analogic Technologies – 1MHz 400mA Step-Down Converter | |||
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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 59kâ¦. 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 59k⦠for good noise
immunity or 221k⦠for reduced no load input current.
R1
=
â VOUT
â VREF
-1ââ
·
R2
=
â 1.5V
â 0.6V
-
1 ââ
·
59kâ¦
=
88.5kâ¦
12
1143.2005.09.1.7
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