AATIAN25 Datasheet, PDF (1/5 Pages) SiGe Semiconductor, Inc. – 850kHz 700mA Buck Regulator

EV-109
AAT1151 QFN EVAL
850kHz 700mA Buck Regulator
Introduction
The AAT1151 evaluation board demonstrates performance, along with the suggested size and placement of
external components, for the AAT1151 integrated buck regulator. The external components are selected for
minimum size and optimum operation up to 700mA output current. The output voltage can be adjusted with
the use of the 1.0V version of the AAT1151 and external resistors R3 and R4. Please refer to the AAT1151
product datasheet for more details about the AAT1151.
Layout
As with all switching power supplies, the board layout for the AAT1151 is critical (see Figure 1). Special care
has been taken with the placement of the external components. The input capacitor (C1) placement is critical.
It must be located immediately adjacent to the AAT1151. As shown in Figure 2, the LX node trace has been
routed under C1 in order to facilitate a close placement of C1 next to the IC. The output voltage feedback
trace has been routed on the portion of backside of the board which has a ground plane on the top side (see
Figure 3). The trace is also routed to avoid the LX node and associated noise.
V_IN+
C1
10µF
Enable
GND
R1
100
R2
100k
C2
0.1µF
U1
AAT1151-QFN
12
VP
4
FB
11
VP
15
LX
10
VP
14
LX
9
VCC
13
LX
7
EN
8
N/C
6
3
SGND PGND
16
2
N/C PGND
5
1
SGND PGND
V_O+
R3
L1
3.3µH
R4
10.0 kΩ
C3-C7
4x 10µF
(2x 22µF)
GND
Figure 1: AAT1151 QFN Evaluation Board Schematic.
Specification
Input Voltage
Output Error Voltage
Output Current
Test Conditions
Min
Typ
2.7
3.6
-3
0
Table 1: AAT1151 QFN Evaluation Board Specifications.
Max
5.5
+3
700
Units
V
%
mA
EV-109.2005.04.1.1
1