AAT1232
24V 100mA Step-Up Converter
Functional Block Diagram
VIN
LIN
VP
Output
Timer
EN/SET
SW
Control
FB1
1.2V
Output
Select
VREF
FB2
SEL
PGND
GND
The AAT1232 modulates the power MOSFET
switching current in response to changes in output
voltage. This allows the voltage loop to directly
program the required inductor current in response
to changes in the output load.
Functional Description
The AAT1232 consists of a DC/DC boost controller,
an integrated slew rate controlled input disconnect
MOSFET switch, and a MOSFET power switch. A
high voltage rectifier, power inductor, output capac-
itor, and resistor divider network are required to
implement a DC/DC boost converter.
The switching cycle initiates when the N-channel
MOSFET is turned ON and current ramps up in the
inductor. The ON interval is terminated when the
inductor current reaches the programmed peak
current level. During the OFF interval, the input
current decays until the lower threshold, or zero
inductor current, is reached. The lower current is
equal to the peak current minus a preset hystere-
sis threshold - which determines the inductor ripple
current. The peak current is adjusted by the con-
troller until the output current requirement is met.
Control Loop
The AAT1232 provides the benefits of current mode
control with a simple hysteretic feedback loop. The
device maintains exceptional DC regulation, tran-
sient response, and cycle-by-cycle current limit with-
out additional compensation components.
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1232.2006.12.1.3
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
