PRODUCT DATASHEET
AAT2146W
TM
SwitchReg
Low Noise, FastTransient 600mA Step-Down Converter
Figure 2: AAT2146W Evaluation Board
Component Side Layout.
Figure 3: Exploded View of AAT2146W
Evaluation Board Component Side Layout.
Figure 4: AAT2146W Evaluation Board
Solder Side Layout.
Adjustable Output Resistor Selection
V
1.5V
OUT
R1 =
-1 · R2 =
- 1 · 59kΩ = 88.5kΩ
FeedbackꢀresistorsꢀR1ꢀandꢀR2ꢀofꢀFigureꢀ5ꢀprogramꢀtheꢀ
output to regulate at a voltage higher than 0.6V. To limit
the bias current required for the external feedback resis-
tor string while maintaining good noise immunity, the
minimumꢀ suggestedꢀ valueꢀ forꢀ R2ꢀ isꢀ 59kW. Although a
larger value will further reduce quiescent current, it will
also increase the impedance of the feedback node, mak-
ing it more sensitive to external noise and interference.
Table 2 summarizes the resistor values for various out-
putꢀvoltagesꢀwithꢀR2ꢀsetꢀtoꢀeitherꢀ59kW for good noise
immunity or 221kW for reduced no load input current.
V
0.6V
REF
The AAT2146W combined with an external feedforward
capacitorꢀ(C4ꢀinꢀFigureꢀ5),ꢀdeliversꢀenhancedꢀtransientꢀ
response for extreme pulsed load applications.
w w w . a n a l o g i c t e c h . c o m
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2146W.2011.02.1.0
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