AAT2505 Datasheet, PDF (12/26 Pages) Advanced Analogic Technologies – Dual Channel, Step-Down Converter/Linear Regulator

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