AATIAN22 Datasheet, PDF (1/11 Pages) SiGe Semiconductor, Inc. – 3MHz Fast Transient 400mA Step-Down Converter

EV-139
AAT1149 EVAL: 3MHz Fast Transient
400mA Step-Down Converter
Introduction
The AAT1149 Evaluation Board provides a platform for test and evaluation of the AAT1149 3MHz Fast
Transient 400mA Step-Down Converter. The evaluation board demonstrates suggested size and placement
of external components to achieve the best performance. The external components are limited and selected
for small size to suit portable device applications while the layout has been optimized to achieve high efficien-
cy and low output noise with the SC70JW-8 package. The design operates across an input voltage range from
2.7V to 5.5V.
The AAT1149 Evaluation Board provides an adjustable output voltage from 1V to V_IN at 400mA maximum out-
put current. Resistors R1 and R2 program the output to regulate at a voltage higher than 0.6V. The suggest-
ed value for R2 is 59kΩ. Table 2 summarizes the resistor values for various output voltages. Connecting EN
to IN will turn on the part while connecting EN to GND will disable the part.
Schematic and BOM
VIN
ON/OFF
C2
4.7μF
SC70JW-8
3
IN
4
LX
1 _EN
2
FB
6
PGND
AAT 1149
5
AGND
L1
1.8μH
R1
C6
Adj.
100pF
(Optional)
R2
59K
VOUT
C1
4.7μF
7
PGND
8
PGND
Figure 1: AAT1149 Evaluation Board Schematic.
Symbol
U1
C1, C2,
C3
L1
R1
R2
Description
AAT1149 SC70JW-8
4.7μF 10V 0805
100pF 10V 0402(Optional)
1.8µH Sumida CDRH2DO9
See Table 2; 10V 0402
59kΩ 10V 0402
Table 1: AAT1149 Evaluation Board Build of Materials (BOM).
EV-139.2007.08.1.0
1