AAT1149 Analogic Corporation, AAT1149 Datasheet - Page 10

• Manufacturer Part Number: AAT1149
• Manufacturer: Analogic Corporation

Functional Block Diagram
Functional Description
The AAT1149 is a high performance 400mA 3.0MHz
monolithic step-down converter. It minimizes exter-
nal component size, enabling the use of a tiny 0603
inductor that is only 1mm tall, and optimizes effi-
ciency 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 (C
and L) are required. Output voltage is programmed
with external feedback resistors, ranging from 1.0V
to the input voltage. An additional feed-forward
10
EN
Reference
Voltage
INPUT
FB
Amp
Err
.
IN
, C
OUT
,
capacitor can also be added to the external feed-
back to provide improved transient response (see
Figure 4).
At dropout, the converter duty cycle increases to
100% and the output voltage tracks the input volt-
age minus the R
side MOSFET.
The input voltage range is 2.7V to 5.5V. The con-
verter efficiency has been optimized for all load
conditions, ranging from no load to 400mA.
The internal error amplifier and compensation pro-
vides excellent transient response, load, and line
regulation. Soft start eliminates any output voltage
overshoot when the enable or the input voltage is
applied.
Logic
400mA Step-Down Converter
DH
DL
DS(ON)
3MHz Fast Transient
IN
drop of the P-channel high-
LX
PGND
AGND
1149.2006.11.1.0