AAT2554
Total Power Solution for Portable Applications
VINB
VINB
ADP
C1
4.7µF
U1
VBAT
ADP
16
11
9
8
1
2
VINB
BAT
OUTA
LX
5
VOUTA
L1
R4
1K
ADP
STAT
VINA
ENA
ENB
C3
4.7µF
VOUTA
VOUTB
C8
15
1
VOUTB
D1
4
FB
R2
118K
ENA
13
3
14
12
10
2
R5
100K
C4
4.7µF
GND
GND
VINB
VINA
100pF
C7
2.2µF
FB
JP2
6
C6
2.2µF
C5
2.2µF
R3
59K
R6
100K
JP3
C8 optional for
enhanced step-
down converter
transient
3
2
1
EN_BAT GND
ADP
7
ISET
GND
response
ENA
R7
100K
JP1
3
2
1
AAT2554
ENB
R1
8.06K
ENB
3
2
1
EN_BAT
GND
EN_BAT
Figure 5: AAT2554 Evaluation Board Schematic.
3. The feedback pin (Pin 1) should be separate
from any power trace and connect as closely as
possible to the load point. Sensing along a high-
current load trace will degrade DC load regula-
tion. Feedback resistors should be placed as
closely as possible to the FB pin (Pin 1) to mini-
mize the length of the high impedance feedback
trace. If possible, they should also be placed
away from the LX (switching node) and inductor
to improve noise immunity.
4. The resistance of the trace from the load return
GND (Pins 2, 10, 12, and 14) should be kept to
a minimum. This will help to minimize any error
in DC regulation due to differences in the poten-
tial of the internal signal ground and the power
ground.
Printed Circuit Board Layout
Considerations
For the best results, it is recommended to physi-
cally place the battery pack as close as possible to
the AAT2554 BAT pin. To minimize voltage drops
on the PCB, keep the high current carrying traces
adequately wide. Refer to the AAT2554 evaluation
board for a good layout example (see Figures 6
and 7). The following guidelines should be used to
help ensure a proper layout.
1. The input capacitors (C1, C3, C7) should con-
nect as closely as possible to ADP (Pin 11),
VINA (Pin 4), and VINB (Pin 16).
2. C4 and L1 should be connected as closely as
possible. The connection of L1 to the LX pin
should be as short as possible. Do not make the
node small by using narrow trace. The trace
should be kept wide, direct, and short.
5. A high density, small footprint layout can be
achieved using an inexpensive, miniature, non-
shielded, high DCR inductor.
26
2554.2007.01.1.2
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