18V 100mA Step-Up Converter
Functional Block Diagram
VIN
AAT1230/1230-1
VP
LIN
Soft-Start
Timer
EN/SET
Control
FB1
V
REF1
Output
Select
V
REF2
FB2
SEL
GND
PGND
SW
Functional Description
The AAT1230/1230-1 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, out-
put capacitor, and resistor divider network are
required to implement a DC/DC boost converter.
output voltage. This allows the voltage loop to
directly program the required inductor current in
response to changes in the output load.
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.
The magnitude of the feedback error signal deter-
mines the average input current. Therefore, the
AAT1230/1230-1 controller implements a pro-
Control Loop
The AAT1230/1230-1 provides the benefits of cur-
rent mode control with a simple hysteretic feedback
loop. The device maintains exceptional DC regula-
tion, transient response, and cycle-by-cycle current
limit without additional compensation components.
The AAT1230/1230-1 modulates the power MOS-
FET switching current in response to changes in
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1230.2006.10.1.4
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
