AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
Functional Block Diagram
VCC
VP
FB
Error
Amp.
DH
See
Note
LX
Logic
Voltage
Reference
DL
Control
Logic
PGND
EN
SGND
VLDO
OUT
Over-Current
Protection
Error
Amp.
Fast Start
Control
ENLDO
POK
Voltage
Reference
94%
+
-
GND
Note: Internal resistor divider included for ≥ 1.2V versions. For low voltage versions, the feedback pin is tied directly to the error amplifier input.
cuit which accelerates the power-up behavior of
fundamental control and feedback circuits within
Functional Description
the LDO regulator. Fast turn-off time response is
The AAT2505 is a high performance power man-
achieved by an active output pull-down circuit,
agement IC comprised of a buck converter and a
which is enabled when the LDO regulator is placed
linear regulator. The high efficiency buck convert-
in shutdown mode. This active fast shutdown cir-
er is capable of delivering up to 600mA. Designed
cuit has no adverse effect on normal device opera-
to operate at 1.4MHz, the converter requires only
tion. The LDO regulator output has been specifi-
three external components (CIN, COUT, and LX) and
cally optimized to function with low-cost, low-ESR
is stable with a ceramic output capacitor. The lin-
ceramic capacitors; however, the design will allow
ear regulator delivers 300mA and also is stable
for operation over a wide range of capacitor types.
with a ceramic output capacitor.
Other features include an integrated Power-OK
comparator which indicates when the output is out of
Linear Regulator
regulation. The POK open-drain output is low when
The advanced circuit design of the linear regulator
OUT is 6% below its nominal regulation voltage. The
has been specifically optimized for very fast start-up
open-drain signal is held low when the linear regula-
and shutdown timing. This proprietary CMOS LDO
tor is in shutdown mode. The regulator comes with
has also been tailored for superior transient response
complete short-circuit and thermal protection. The
characteristics. These traits are particularly important
combination of these two internal protection circuits
for applications that require fast power supply timing.
gives a comprehensive safety system to guard
The high-speed turn-on capability is enabled
through implementation of a fast-start control cir-
against extreme adverse operating conditions.
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2505.2006.06.1.1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
