AAT1154 Advanced Analogic Technologies, AAT1154 Datasheet - Page 14

• Manufacturer Part Number: AAT1154
• Description: 1MHz 3A Buck DC/DC Converter
• Manufacturer: Advanced Analogic Technologies

Input Capacitor
The input capacitor ripple is:
In the examples shown C1 is a ceramic capacitor
located as close to the IC as possible. C1 provides
the low impedance path for the sharp edges asso-
ciated with the input current. C4 may or may not be
Adjustable Output
For applications requiring an output other than the
fixed outputs available, the 1V version can be pro-
grammed externally. Resistors R3 and R4 of figure 5
force the output to regulate higher than 1 Volt. For
14
100µF
Vin 3.5V-5.5V
C4
rtn
10µF
C1
Figure 3. 3.3 Volt 3 Amp Output
I
C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C2 Vishay 120µF 6.3V 594D127X96R6R3C2T
C3 0. 1 µF 0603ZD104M AVX
C4 Vishay Sprague 100µF 16V 595D107X0016C 100µF 16V
D1 B340LA Diodes Inc.
L1 CDRH6D28-1.5µH Sumida
Options
C2 MuRata 100µF 6.3V GRM43-2 X5R 107M 100µF 6.3V (two or three in parallel
C2 TDK 100µF 6.3V C3325X5R0J107M 100µF 6.3V (two or three in parallel)
RMS
R1
100
=
I
R2
100k
O
C3
0.1µF
·
V
V
O
IN
·
AAT1154-3. 3
FB
GND
EN
VCC
1
U1
-
LX
LX
V
VP
VP
V
IN
O
=
1.42
Arms
Vout 3. 3 V @ 3A
B340LA
D1
L1
1.5µH
C2
120µF
+
-
required depending upon the impedance charac-
teristics looking back into the source. It serves to
dampen out any input oscillations that may arise
from a source that is highly inductive. For most
applications where the source has sufficient bulk
capacitance and is fed directly to the AA1154
through large PCB traces or planes it is not
required. When operating the AAT1154 evaluation
board on the bench C4 is required due to the
inductance of the wires running from the laborato-
ry power supply to the evaluation board.
accurate results (less than 1% error for all outputs)
select R4 to be 10k . Once R4 has been selected
R3 can be calculated. For a 1.25 Volt output with R4
set to 10k R3 is 2.5k .
100
1MHz 3A Buck DC/DC Converter
95
90
85
80
75
70
65
60
Figure 4. 5 Volt Input 3.3 Volt Output
0.01
R3 = (V
Efficiency vs. Load Current
O
V
- 1) · R4 = 0.25 · 10k = 2.5k
IN
Output Current (A)
= 5.0V, V
0.1
OUT
= 3.3V
1
AAT1154
1154.2003.08.0.91
10