AAT1149 查看數據表（PDF） - Advanced Analogic Technologies
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AAT1149 Datasheet PDF : 21 Pages
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Functional Block Diagram
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PRODUCT DATASHEET
AAT1149
3MHz Fast Transient 400mA Step-Down Converter
IN
Err
Am. p
Voltage
Reference
EN
INPUT
DH
Logic
DL
LX
PGND
AGND
Functional Description
The AAT1149 is a high performance 400mA 3.0MHz
monolithic step-down converter. It minimizes external
component size, enabling the use of a tiny 0603 inductor
that is only 1mm tall, and optimizes efficiency over the
complete load range. Apart from the small bypass input
capacitor, only a small L-C filter is required at the output.
Typically, a 1.8μH inductor and a 4.7μF ceramic capacitor
are recommended (see table of values).
Only three external power components (CIN, COUT, and L)
are required. Output voltage is programmed with exter-
nal feedback resistors, ranging from 1.0V to the input
voltage. An additional feed-forward capacitor can also be
added to the external feedback to provide improved
transient response (see Figure 4).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the RDS(ON) drop of the P-channel high-side MOSFET.
The input voltage range is 2.7V to 5.5V. The converter
efficiency has been optimized for all load conditions,
ranging from no load to 400mA.
The internal error amplifier and compensation provides
excellent transient response, load, and line regulation.
Soft start eliminates any output voltage overshoot when
the enable or the input voltage is applied.
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1149.2008.08.1.3
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