PRODUCT DATASHEET
AAT2784
SystemPowerTM
3-Channel Step-Down DC/DC Converter
Functional Block Diagram
VP3
Comp.
FB3
EN3
Error
Amp
Logic
LX3
Control
Logic
PGND3
VP1_2
OT
OSC
Comp.
FB2
EN2
Error
Amp
Logic
LX2
Control
Logic
PGND2
AGND
IN
OSC
Comp.
FB1
EN1
Error
Amp
Logic
LX1
Voltage
Ref
Control
Logic
PGND1
Soft start limits the current surge seen at the input and
eliminates output voltage overshoot. The enable inputs,
when pulled low, force the respective converter into a
low power non-switching state consuming less than 1μA
of current.
Functional Description
The AAT2784 is a high performance power management
IC comprised of 3 buck converters. Each channel has an
independent enable pin. Operating at a switching fre-
quency of 1.8MHz, the converter requires a minimum of
small external components, reducing the solution cost
and PCB footprint.
For overload conditions, the peak input current is limit-
ed. Also, thermal protection completely disables switch-
ing if internal dissipation becomes excessive, thus pro-
tecting the device from damage. The junction over-
temperature threshold is 140˚C with 15˚C of hysteresis.
Under-voltage lockout (UVLO) guarantees sufficient VIN
bias and proper operation of all internal circuits prior to
activation.
All converters operate with an input voltage range of
2.7V to 5.5V. The output voltage range is 0.6V to VIN
and is adjustable with an external resistor divider.
Channel 3 power devices are sized for 1.5A output cur-
rent. Channels 1 and 2 power devices are sized for
300mA output current while maintaining over 85% effi-
ciency at full load. Peak efficiency is above 95%. Light
load efficiency is maintained at greater than 80% down
to 85% of full load current. All channels have excellent
transient response, load and line regulation. Transient
response time is typically less than 20μs.
Control Loop
The AAT2784 is a peak current mode step-down con-
verter. The current through the P-channel MOSFET (high
side) is sensed for current loop control, as well as short-
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