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PDF AAT2785 Data sheet ( Hoja de datos )
| Número de pieza | AAT2785 | |
| Descripción | 3-Channel Step-Down DC/DC Converter | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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SystemPowerTM
PRODUCT DATASHEET
AAT2785
3-Channel Step-Down DC/DC Converter
General Description
Features
The AAT2785 is a 3-channel 1.8MHz step-down con-
verter for applications where power efficiency and solu-
tion size are critical. The input voltage range is 2.7V to
5.5V and the outputs are adjustable from 0.6V to VIN.
The AAT2785 incorporates a unique low noise architec-
ture which reduces ripple and spectral noise. Channel 3
delivers up to 1.5A output current and channels 1 and 2
deliver up to 600mA each. The AAT2785 uses a high
switching frequency to minimize the size of external com-
ponents. The AAT2785 requires a minimum of external
components to realize a high efficiency triple-output buck
converter minimizing solution cost and PCB footprint.
Each of the 3 regulators has an independent enable pin,
adjustable output voltage and operates with low no load
quiescent current, providing high efficiency over the
entire load range.
The AAT2785 is available in a Pb-free 16 pin TDFN34
package, and is rated over the -40°C to +85°C operating
temperature range.
• VIN Range: 2.7 to 5.5V
• Output Voltage Range: 0.6V to VIN
• Output Current:
▪ Channel 3: 1.5A
▪ Channel 1: 600mA
▪ Channel 2: 600mA
• Low Noise Light Load Mode
• Low Ripple PWM Mode
• Highly Efficient Step-Down Converters
• Low RDS(ON) Integrated Power Switches
• 100% Duty Cycle
• 1.8MHz Switching Frequency
• Internal Soft Start
• Fast 150μs Turn-On Time
• Over-Temperature Protection
• Current Limit Protection
• TDFN34-16 Package
• -40°C to 85°C Temperature Range
Applications
Typical Application
• Cellular and Smart Phones
• Digital Cameras
• Handheld Instruments
• Mass Storage Systems
• Microprocessor / DSP Core / IO Power
• PDAs and Handheld Computers
• Portable Media Players
• USB Devices
• Wireless LAN
VIN: 2.7V–5.5V
C1
10μF
C2
10μF
IN LX1
AAT2785
FB1
VP1_2
EN1
LX2
FB2
EN2 PGND
VP3
EN3
GND
LX3
FB3
PGND
L1
4.7μH
L2
4.7μH
L3
1.5μH
VOUT1: 3.3V, 600mA
VOUT2: 3.3V, 600mA
R1
133k
R2
29.4k
C3
4.7μF
R3
133k
R4
29.4k
C4
4.7μF
VOUT3: 1.2V, 1.5A
R5
59.0k
R6
59.0k
C5
10μF
2785.2008.01.1.0
www.analogictech.com
1
1 page  
SystemPowerTM
Typical Characteristics
105
95
85
75
65
55
45
35
25
15
0.1
Efficiency vs. Output Current
(Channel 1, 2; VOUT = 3.3V)
VIN = 3.6V
VIN = 4.2V
VIN = 5V
1 10 100 1000
Output Current (mA)
100
90
80
70
60
50
40
30
20
10
0
0.1
Efficiency vs. Output Current
(Channel 3; VOUT = 1.2V)
VIN = 4.2V
VIN = 3.6V
VIN = 2.7V
1 10 100 1000
Output Current (mA)
10000
Switching Frequency vs. Input Voltage
10
8
6
4
2
0
-2
-4
-6
Channel 3
-8 Channel 1, 2
-10
2.3 2.8 3.3 3.8 4.3 4.8 5.3 5.8
Input Voltage (V)
PRODUCT DATASHEET
AAT2785
3-Channel Step-Down DC/DC Converter
3
2
1
0
-1
-2
-3
-4
-5
0.1
Load Regulation
(Channel 1, 2; VOUT = 3.3V)
VIN = 5V
VIN = 4.2V
VIN = 3.6V
1 10 100
Output Current (mA)
1000
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
0.1
Load Regulation
(Channel 3; VOUT = 1.2V)
VIN = 4.2V
VIN = 3.6V
VIN = 2.7V
1 10 100 1000
Output Current (mA)
10000
Output Error vs. Temperature
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
-40
Channel 3
Channel 1, 2
-15 10 35 60 85
Temperature (°C)
2785.2008.01.1.0
www.analogictech.com
5
5 Page 
SystemPowerTM
Functional Block Diagram
PRODUCT DATASHEET
AAT2785
3-Channel Step-Down DC/DC Converter
VP3
FB3
EN3
FB2
EN2
AGND
IN
FB1
EN1
Error
Amp
Comp.
Control
Logic
Logic
OT OSC
Error
Amp
Comp.
Control
Logic
Logic
OSC
Error
Amp
Comp.
Voltage
Ref
Control
Logic
Logic
LX 3
PGND3
VP1_2
LX2
PGND2
LX1
PGND1
Functional Description
The AAT2785 is a high performance power management
IC comprised of 3 buck converters. Each channel has an
independent input voltage and enable pin. Operating at
a switching frequency 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 VIN and
is adjustable with an external resistor divider. Channel 3
power devices are sized for 1.5A output current.
Channels 1 and 2 power devices are sized for 600mA
output current while maintaining over 85% efficiency at
full load. Peak efficiency is above 95%. Light load effi-
ciency 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.
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 limited.
Also, thermal protection completely disables switching if
internal dissipation becomes excessive, thus protecting
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.
2785.2008.01.1.0
www.analogictech.com
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet AAT2785.PDF ] | |
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