AAT1152 Просмотр технического описания (PDF) - Advanced Analogic Technologies
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AAT1152 Datasheet PDF : 17 Pages
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AAT1152
850kHz 1A Buck DC/DC Converter
R5
100k
POK
VIN+ 3.3V
C1
10μF
R1 100
EN
R2
100k
C2
0.1μF
U1
AAT1152-1.0
VP
FB
VCC POK
EN
LX
SGND PGND
R3
2.55k 1%
VO+ 1.25V 1A
R4
10k 1%
L1
LX 2.7μH
C3, C4, C5
3x 22μF
6.3V
V-
C1 Murata 10μF 6.3V X5R GRM42-6X 5R106K6.3
C3, C4, C5 MuRata 22μF 6.3V GRM21BR60J226ME39L X5R 0805
L1 Sumida CDRH4D28-2R 7μH
Figure 3: 3.3V to 1.25V Converter.
R5
100k
POK
VIN + 2.7V - 5.5V
C1
10μF
R1 100
R2
EN
100k
C2
0.1μF
U1
AAT1152-1.5
VP
FB
VCC POK
EN
LX
SGND PGND
VO+ 1.5V 1A
L1
4.1μH
LX
C3, C4, C5
3x 22μF
6.3V
V-
C1 Murata 10μF 6.3V X5R GRM42-6X5R106K6.3
C3, C4, C5 MuRata 22μF 6.3V GRM21BR60J226ME39L X5R 0805
L1 Sumida CDRH5D 18-4R 1μH
100
80
60
40
20
0
10
Efficiency vs. Output Current
(VOUT = 1.5V)
2.7V
4.2V
3.6V
100
1000
Output Current (mA)
Figure 4: Lithium-Ion to 1.5V Output Converter.
Power Good
The AAT1152 features an integrated POK com-
parator and open-drain output signal. The POK pin
goes low when the converter output is 12% or more
below its nominal regulation voltage or when the
device is in shutdown. Connect a pull-up resistor
from POK to the converter input or output. Typical
resistor pull-up values range from 100k to 10k.
Inductor
The output inductor is selected to limit the ripple
current to some predetermined value, typically 20%
to 40% of the full load current at the maximum input
voltage. Manufacturer's specifications list both the
inductor DC current rating, which is a thermal limi-
tation, and the peak current rating, which is deter-
mined by the saturation characteristics. The induc-
tor should not show any appreciable saturation
under normal load conditions. During overload and
short-circuit conditions, the average current in the
inductor can meet or exceed the ILIMIT point of the
AAT1152 without affecting converter performance.
Some inductors may have sufficient peak and aver-
age current ratings yet result in excessive losses
due to a high DCR. Always consider the losses
associated with the DCR and its effect on the total
converter efficiency when selecting an inductor.
1152.2006.09.1.7
11
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