PRODUCT DATASHEET
AAT2503178
SystemPower
TM
Pin Descriptions
Pin #
1
2
3
4
Adjustable 3-Channel Regulator
Symbol
FBB
ENA
ENB
MODE/SYNC
Function
Feedback input pin for LDOB. This pin is connected to OUTB via an external resistor. It is used to see the
output of LDOB to regulate to the desired value via an external resistor divider. For
fi
xed versions, short
FBB to OUTB.
Enable pin for LDOA. When connected low, LDOA is disabled and consumes less than 1μA of current. When
connected high, normal operation.
Enable pin for LDOB. When connected low, LDOB is disabled and consumes less than 1μA of current. When
connected high, normal operation.
Connect to ground for PWM/PFM mode and optimized efficiency throughout the load range. Connect high
for low noise PWM operation under all operating conditions. Connect to an external clock for synchroniza-
tion (PWM only).
Feedback input pin for the step-down converter. This pin is connected to the converter output via an ex-
ternal resistor. It is used to see the output of the converter to regulate to the desired value via an external
resistor divider.
Ground connection pin.
Main power ground return pin for the step-down converter. Connect to the output and input capacitor return.
Connect inductor to this pin. Switching node internally connected to the drain of both high- and low-side
MOSFETs.
Input supply voltage for the converter. Must be closely decoupled.
Not connected.
Bias supply. Supply power for the internal circuitry. Connect to input power via low pass
fi
lter with decou-
pling to AGND.
Enable for the step-down converter. A logic low disables the converter and it consumes less than 1μA of
current. A logic high enables normal operation.
Power-OK pin with open drain output. It is pulled low when the OUTA pin is outside the regulation window.
Place a pull-up resistor between POK and OUTA.
Feedback input pin for LDOA. This pin is connected to OUTA via an external resistor. It is used to see the
output of LDOA to regulate to the desired value via an external resistor divider. For
fi
xed versions, short
FBA to OUTA.
LDOA output pin; should be closely decoupled with a low-ESR ceramic capacitor.
Input voltage pin for linear regulator A; should be closely decoupled.
Input voltage pin for linear regulator B; should be closely decoupled.
LDOB output pin; should be closely decoupled with a low-ESR ceramic capacitor.
Exposed paddle; connect to ground directly beneath the package.
5
6
7
8, 9
10
11, 12
13
14
15
16
17
18
19
20
EP
FB
AGND
PGND
LX
VP
N/C
VIN
EN
POK
FBA
OUTA
VLDOA
VLDOB
OUTB
2
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2503.2008.02.1.4
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