AAT1154(2003) Ver la hoja de datos (PDF) - Analog Technology Inc
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AAT1154 Datasheet PDF : 16 Pages
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AAT1154
1MHz 3A Buck DC/DC Converter
Input Capacitor
The input capacitor ripple is:
IRMS = IO ·
VO · 1- VO = 1.42Arms
VIN VIN
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
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.
Vin 3.5V-5.5V
C4
100µF
R1 R2
100 100k
C1
10µF
C3
0.1µF
U1
AAT1154-3. 3
FB VP
GND LX
EN LX
VCC VP
Vout 3.3V @ 3A
L1
1.5µH
D1
C2
B340LA 120µF
+
-
rtn C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C2 Vishay120µF 6.3V 594D127X96R6R3C2T
C3 0.1µF 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)
Figure 3. 3.3 Volt 3 Amp Output
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
Efficiency vs. Load Current
VIN = 5.0V, VOUT = 3.3V
100
95
90
85
80
75
70
65
60
0.01
0.1
1
10
Output Current (A)
Figure 4. 5 Volt Input 3.3 Volt Output
accurate results (less than 1% error for all outputs)
select R4 to be 10kΩ. Once R4 has been selected
R3 can be calculated. For a 1.25 Volt output with R4
set to 10k R3 is 2.5kΩ.
R3 = (VO - 1) · R4 = 0.25 · 10kΩ = 2.5kΩ
14
1154.2003.08.0.91
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