AAT2784 Analogic Corporation, AAT2784 Datasheet - Page 11

• Manufacturer Part Number: AAT2784
• Manufacturer: Analogic Corporation

SystemPower
SystemPower
Functional Block Diagram
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.
All converters operate with an input voltage range of
2.7V to 5.5V. The output voltage range is 0.6V to V
and is adjustable with an external resistor divider.
Channel 3 power devices are sized for 1.5A output cur-
rent.
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.
2784.2007.11.1.1
2784.2007.11.1.1
Channels 1 and 2 power devices are sized for
TM
TM
AGND
EN1
EN3
EN2
FB3
FB2
FB1
IN
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w w w . a n a l o g i c t e c h . c o m
Voltage
Ref
Error
Amp
Error
Amp
Error
Amp
Control
Control
Control
Logic
Logic
Logic
IN
Comp.
Comp.
Comp.
OT
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.
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 V
bias and proper operation of all internal circuits prior to
activation.
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-
3-Channel Step-Down DC/DC Converter
3-Channel Step-Down DC/DC Converter
Logic
Logic
Logic
OSC
OSC
LX 3
PGND3
LX2
LX1
PGND1
VP3
PGND2
PRODUCT DATASHEET
PRODUCT DATASHEET
VP1_2
AAT2784
AAT2784
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IN