AAT2503
Adjustable 3-Channel Regulator
Functional Block Diagram
FB
VP
VIN
Voltage
Reference
DH
Err.
Amp.
LX
MODE/SYNC
Logic
Control
Logic
DL
PGND
OUTA
EN
VLDOA
ENB
Over-Current
Protection
VLDOB
ENA
Err.
Amp.
Voltage
Reference
FBA
POK
94ꢀ
VREF
OUTB
FBB
AGND
operation maintains high efficiency under light load
conditions (typically <50mA). The MODE/SYNC pin
allows an optional "PWM Only" mode. This main-
tains constant frequency and low output ripple
across all load conditions. Alternatively, the IC can
be synchronized to an external clock via the
MODE/SYNC input. External synchronization is
maintained between 1MHz and 3MHz. It consumes
30µA of typical no load quiescent current, making it
also ideal for light load applications. The oscillator
operates at 2MHz, minimizing the cost and size of
external components.
Functional Description
The AAT2503 is a high performance power man-
agement IC comprised of a step-down converter
and two linear regulators. The step-down convert-
er operates in both fixed and variable frequency
modes for high efficiency performance. The switch-
ing frequency is 2MHz, minimizing the size of the
inductor. The converter requires only three external
components (CIN, COUT, and L). The LDOs can
deliver up to 150mA each. Each regulator has
independent input voltage and enable pins and
operates with ceramic capacitors.
A logic low on the EN pin shuts the converter down
and makes it consume less than 1µA of current.
Switch-Mode Step-Down Converter
Soft start increases the inductor current limit point
in discrete steps when the input voltage or enable
input is applied. It limits the current surge seen at
the input and eliminates output voltage overshoot.
The switching regulator is a monolithic step-down
converter operating with input voltage range of 2.7V
to 5.5V. Power devices are sized for 800mA current
capability and achieve over 95ꢀ efficiency. PFM
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2503.2007.04.1.1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
