AAT1143 Advanced Analogic Technologies, AAT1143 Datasheet - Page 12

• Manufacturer Part Number: AAT1143
• Description: 1MHz 400mA Step-Down Converter
• Manufacturer: Advanced Analogic Technologies

The maximum output capacitor RMS ripple current
is given by:
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
12
Figure 2: AAT1143 Evaluation Board
I
RMS(MAX)
=
2
·
1
3
Top Side.
·
V
OUT
L · F · V
· (V
IN(MAX)
IN(MAX)
Figure 4: AAT1143 Evaluation Board
- V
OUT
)
Bottom Side.
1MHz 400mA Step-Down Converter
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 =
Figure 3: Exploded View of Evaluation
⎛
⎝
V
V
OUT
REF
-1 · R2 =
Board Top Side Layout.
⎞
⎠
⎛
⎝
1.5V
0.6V
- 1 · 59kΩ = 88.5kΩ
⎞
⎠
AAT1143
1143.2005.09.1.7