AATIAN27 Datasheet, PDF (1/4 Pages) SiGe Semiconductor, Inc. – 1MHz 3A Buck DC/DC Switch Mode Regulator

EV-104
AAT1154EVAL
1MHz 3A Buck DC/DC Switch Mode Regulator
Introduction
The AAT1154 evaluation board demonstrates performance, along with the suggested size and placement of
external components, for the AAT1154 integrated buck regulator. The external components are selected for
minimum size and optimum operation up to 3.0A output current. Please refer to the AAT1154 datasheet for
more details about this product.
Component Summary
Capacitor C4 is a high equivalent series resistance (ESR) tantalum for damping the high Q input network asso-
ciated with the inductance of the leads feeding the input power to the evaluation board and the low ESR 10µF
ceramic input capacitor (C1). R2 is a pull-up resistor to allow the enable pin to be used to enable and disable
the IC by either shorting the enable pin to GND or leaving the pin open. Both R2 and C4 are for demonstra-
tion purposes only and are not necessary in the final solution. Resistors R3 and R4 are used with the 1V model
to set the out voltage to any desired value from 1V to as high as 200mV below the minimum input voltage.
They are not required for the fixed output voltage versions of the AAT1154. For fixed output voltage versions,
R4 is omitted and R3 is replaced with a short.
Layout
As with all switching power supplies, the board layout for the AAT1154 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 placed immediately adjacent to the AAT1154. As can be seen in Figure 2, the LX node trace has
been routed under C1 in order to facilitate placement of C1 close to the IC. The output voltage feedback trace
has been routed on the portion of the back side of the board which has a ground plane on the top side (see
Figure 3). The trace is routed to avoid the LX node and associated noise. Please refer to Table 1 for AAT1154
evaluation board specifications.
V_IN+
C4
100µF
Enable
R1
100
R2
100k
C1
10µF
C3
0.1µF
R3
R4
10.0k
U1
AAT1154
1
FB
8
VP
2
7
GND LX
3
EN
6
LX
4
5
VCC VP
CR1
B340LA
V_O+
L1
1.5uH
C2
120µF
GND
Figure 1: AAT1154 Evaluation Board Schematic.
EV-104.2005.01.1.0
1