AAT1162
12V, 1.5A Step-Down DC/DC Converter
Functional Block Diagram
AIN
LDO
IN
Note1
FB
Internal
Power
LDO
Current
Sense Amp
+
-
+
-
+
-
Error
Amp
Control
Logic
Current
Mode
LX
Comparator
Reference
PGND
AGND
EN
DGND
COMP
.
Note1: For fixed output voltage versions, FB is connected to the
error amplifier through the resistive voltage divider shown.
Control Loop
Functional Description
The AAT1162 regulates the output voltage using
constant frequency current mode control. The
AAT1162 monitors current through the high-side P-
channel MOSFET and uses that signal to regulate
the output voltage. This provides improved tran-
sient response and eases compensation. Internal
slope compensation is included to ensure the cur-
rent "inside loop" stability.
The AAT1162 is a current-mode step-down DC/DC
converter that operates over a wide 4V to 13.2V
input voltage range and is capable of supplying up
to 1.5A to the load with the output voltage regulated
as low as 0.6V. Both the P-channel power switch
and N-channel synchronous rectifier are internal,
reducing the number of external components
required. The output voltage is adjusted by an exter-
nal resistor divider; fixed output voltage versions are
available upon request. The regulation system is
externally compensated, allowing the circuit to be
optimized for each application. The AAT1162
includes cycle-by-cycle current limiting, frequency
foldback for improved short-circuit performance, and
thermal overload protection to prevent damage in
the event of an external fault condition.
High efficiency is maintained under light load con-
ditions by automatically switching to variable fre-
quency Light Load control. In this condition, transi-
tion losses are reduced by operating at a lower fre-
quency at light loads.
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1162.2007.09.1.2
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
