AAT2504_08 Datasheet, PDF (11/21 Pages) Advanced Analogic Technologies – Adjustable 3-Channel Regulator

SystemPower^TM
Functional Block Diagram
FB
PRODUCT DATASHEET
AAT2504178
Adjustable 3-Channel Regulator
VIN
VP
MODE/SYNC
EN
VLDOA
ENB
Voltage
Reference
Err.
Amp.
Control
Logic
DH
Logic
DL
VLDOB
OUTB
Err.
Amp.
Voltage
Reference
90%
VREF
LX
PGND
OUTA
ENA
FBA
POK
FBB AGND
Functional Description
The AAT2504 is a high performance power management
IC comprised of a step-down converter and two linear
regulators. The step-down converter operates in both
fixed and variable frequency modes for high efficiency
performance. The switching frequency is 2MHz, minimiz-
ing the size of the inductor. The converter requires only
three external power components (C_IN, C_OUT, and L). Each
LDO can deliver up to 300mA. Each regulator has inde-
pendent input voltage and enable pins and operates with
ceramic capacitors.
Switch-Mode Step-Down Converter
The switching regulator is a monolithic step-down con-
verter operating with input voltage range of 2.7V to 5.5V.
Power devices are sized for 800mA current capability and
achieves over 95% efficiency. The internal oscillator
operates at 2MHz, minimizing the cost and size of exter-
nal components. Light Load operation maintains high
efficiency under light load conditions (typically <50mA)
when MODE/SYNC is grounded. The MODE/SYNC pin tied
high allows optional “PWM Only” operation. This main-
tains constant frequency and low output ripple across all
load conditions. Alternatively, by connecting an external
clock to the AAT2504’s MODE/SYNC pin, the internal
clock is disabled. The external synchronization must stay
between 1MHz and 3MHz.
The current through the P-channel MOSFET (high side)
is sensed for current loop control, as well as short-circuit
and overload protection. A fixed slope compensation sig-
nal is added to the sensed current to maintain stability
for duty cycles greater than 50%. The peak current
mode loop appears as a voltage-programmed current
source in parallel with the output capacitor.
2504.2008.02.1.2
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