PRODUCT DATASHEET
AAT2687
SystemPower
TM
PMIC Solution for 24V Systems with 2 High Performance Step-Down Converters
Functional Block Diagram
VINT
VL1
Reg.
IN1
OSC
OT
FB1
COMP1
Error
Amp
Comp.
Comp.
BST1
Logic
Control
Logic
Voltage
Ref 1
Ref
EN1
LX1
20Ω
Comp
OT
V
OCP1
= 0.1V
RS1
OS1
IN2
OCP
FB_LDO
Error
Amp
OUT2
Logic
FB_LDO
Voltage
Ref 2
Control
Logic
EN2
GND
Functional Description
The AAT2687 provides two independently regulated DC
outputs, consisting of a high voltage step-down regulator
and a low input voltage linear low dropout (LDO) regula-
tor. The PMIC is optimized for low cost 12V adapter inputs,
making the device an ideal system-on-a-chip power solu-
tion for consumer communications equipment.
Channel 1 is a step-down regulator with an input voltage
range 6.0 to 24V, providing up to 4.5A output current.
The 490kHz fixed switching frequency allows small L/C
filtering components.
Channel 1 utilizes voltage mode control configured for
optimum performance across the entire output voltage
and load range. The controller includes integrated over-
current, soft-start and over-temperature protection. Over-
current is sensed through the output inductor DC winding
resistance (DCR). An external resistor network adjusts
the current limit according to the DCR of the desired
inductor and the desired output current limit. Frequency
reduction limits over-current stresses during short-circuit
events. The operating frequency returns to the nominal
setting when over-current conditions are removed.
Channel 2 is a linear low-dropout (LDO) regulator provid-
ing up to 600mA output current at a factory set output
voltage. The device provides extremely low output noise,
low quiescent current and excellent transient response.
The controller includes integrated over-current, soft-
start and over-temperature protection. Independent
input and enable pins provide maximum design flexibil-
ity. The AAT2687 is available in the Pb-free, 4x5mm
24-pin TQFN package. The rated operating temperature
range is -40°C to 85°C.
2687.2008.06.1.0
www.analogictech.com
9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
