PRODUCT DATASHEET
AAT2146
SwitchReg
TM
Functional Block Diagram
OUT
VIN
Low Noise, Fast Transient 600mA Step-Down Converter
See note
Err
Amp
.
DH
Voltage
Reference
Logic
LX
EN
INPUT
DL
PGND
AGND
Note: For adjustable version, the internal feedback divider is omitted and the OUT pin is tied directly
to the internal error amplifier.
Functional Description
The AAT2146 is a high performance 600mA 2MHz mono-
lithic step-down converter. It has been designed with the
goal of minimizing external component size and optimiz-
ing efficiency over the complete load range, and pro-
duces reduced ripple and spectral noise. Apart from the
small bypass input capacitor, only a small L-C filter is
required at the output. Typically, a 4.7μH inductor and a
4.7μF ceramic capacitor are recommended (see table of
values).
The fixed output version requires only three external
power components (C
IN
, C
OUT
, and L). The adjustable ver-
sion can be programmed with external feedback to any
voltage, ranging from 0.6V to the input voltage. An addi-
tional feed-forward capacitor can also be added to the
external feedback to provide improved transient response
(see Figure 1).
At dropout, the converter duty cycle increases to 100%
and the output voltage tracks the input voltage minus
the R
DSON
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 600mA.
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.
2146.2008.10.1.2
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