AAT2505 Analogic Corporation, AAT2505 Datasheet - Page 12

• Manufacturer Part Number: AAT2505
• Manufacturer: Analogic Corporation

Functional Block Diagram
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
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-
12
ENLDO
SGND
VLDO
POK
EN
FB
IN
, C
OUT
Note
See
, and L
Fast Start
Control
Reference
Voltage
VCC
Error
Amp.
X
) and
+
-
Control
Logic
Reference
Voltage
94%
Error
Amp.
Over-Current
Protection
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.
Logic
GND
DH
DL
Converter/Linear Regulator
Dual Channel, Step-Down
VP
LX
PGND
OUT
2505.2006.06.1.1