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PDF AAT2868 Data sheet ( Hoja de datos )
| Número de pieza | AAT2868 | |
| Descripción | constant-frequency charge pump DC/DC converter | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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PRODUCT DATASHEET
AAT2868
SystemPowerTM CABC Compatible 4 Channel Backlight Driver with Dual LDO Regulators
General Description
The AAT2868 is a low-noise, constant-frequency charge
pump DC/DC converter that uses a dual-mode load switch
(1x) and fractional (1.5x) conversion to maximize effi-
ciency for white LED Content Adaptive Brightness Control
(CABC) applications. The AAT2868 is capable of driving 4
white LEDs at a total 124mA from a 2.7V to 5.5V input.
The current sinks may be operated individually or in par-
allel for driving higher-current LEDs. A low external parts
count (two 1μF flying capacitors and two small 1μF capac-
itors at IN and OUTCP) makes the AAT2868 ideally suited
for small battery-powered applications. The AAT2868 also
includes two 150mA low dropout (LDO) linear regulators
as additional power supplies for display and related cam-
era power. The LDO voltage is also programmable.
AnalogicTech’s Advanced Simple Serial Control™
(AS2Cwire™) serial digital input is used to enable, dis-
able and set the maximum LED current to one of 32
levels for the LEDs. The current ranges from 31mA to
0.4mA. An external PWM input is adopted to dim the LED
current from 100% to 1% of the maximum LED current
by varying the PWM duty cycle with frequencies up to
100kHz. To eliminate flicker or noise associated with
PWM control, the input PWM signal is filtered to provide
a steady state output current.
Each output of the AAT2868 is equipped with built-in
protection for short-circuit and auto-disable for load
short-circuit conditions. The soft-start circuitry prevents
excessive inrush current at charge pump start-up and
mode transitions.
The AAT2868 is available in the Pb-free, space-saving
TQFN3.0x2.2-18L package, and operates over the -40°C
to 85°C ambient temperature range.
Features
• 2.7V to 5.5V Supply Voltage Range
• Charge Pump for LED Driver
▪ Dual Mode 1x/1.5x
▪ Drives Up to 4 LEDs with up to 31mA each
▪ Linear LED Output Control Options
• Maximum LED Current Set by AS2Cwire
Interface, 32 Steps
• PWM Interface Dimming from 100% to 1% Duty
Cycle with Frequency up to 100kHz
• 0.9MHz Constant Frequency
• Automatic Soft-Start Limits Inrush Current
• Dual 150mA LDOs
▪ Enable and Output Voltage Set by AS2Cwire
Sixteen Combinations of 5 Output Voltages:
1.2V, 1.5V, 1.8V, 2.8V, and 3.0V
▪ Integrated Discharge Resistor when Disabled
• < 1.0μA in Shutdown
• Short-Circuit Protection
• Small Application Circuit
• -40°C to 85°C Temperature Range
• RoHS Compliant, Halogen-Free TQFN3.0x2.2-18
Package
Applications
• Camera Phones
• Digital Still Cameras (DSC)
• LED Photo Flash/Torch
• MP3 Players
• PDAs and Notebook PCs
• Smartphones
Typical Application
VIN
2.7~5.5V
C1
1μF
CIN
2.2μF
AS2Cwire
PWM
CF
56nF
C1+ C2+
C1- C2-
IN OUTCP
INLDO
AAT2868
EN/SET
PWM
FCAP
D1
D2
D3
D4
LDOA
LDOB
GND AGND
C2
1μF
COUT
1μF
WLEDs
D1 D2 D3
D4
LDOB
CLDOB
2.2μF
LDOA
CLDOA
2.2μF
2868.2010.01.1.0
www.DataSheet.in
www.analogictech.com
1
1 page  
PRODUCT DATASHEET
AAT2868
SystemPowerTM CABC Compatible 4 Channel Backlight Driver with Dual LDO Regulators
Electrical Characteristics (continued)1
VIN = 3.6V; CIN = 1μF; COUT = 1μF; CFLY = 1μF; CFLT = 56nF; TA = -40°C to 85°C, unless otherwise noted. Typical values
are TA = 25°C.
Symbol Description
Linear Regulators
ΔVOUT[A/B]/
VOUT[A/B]
IOUT[A/B](MAX)
VOUT[A/B](DO)
ΔVOUT/
VOUT*ΔVIN
PSRR[A/B]
ROUT_(DCHG)
Thermal
TSD
THYS
LDOA, LDOB Output Voltage Tolerance
LDOA, LDOB Maximum Load Current
LDOA, LDOB2
Line Regulation
LDOA, LDOB Power Supply Rejection Ratio
LDOA, LDOB Auto-Discharge Resistance
TJ Thermal Shutdown Threshold
TJ Thermal Shutdown Hysteresis
Conditions
IOUT = 1mA to 150mA; TA = 25°C
IOUT = 1mA to 150mA; TA = -40°C to +85°C
VOUT[A/B] ≥ 3.0V; IOUT = 150mA
VIN = (VOUT[A/B] + 1V) to 5V
IOUT[A/B] = 10mA, 1kHz
Min Typ Max Units
-2
-3.0
200
100
0.09
50
720
2
3.0
150
%
%
mA
mV
%/V
dB
Ω
140 °C
20 °C
1. The AAT2868 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
2. VDO[A/B] is defined as VIN – LDO[A/B] when LDO[A/B] is 98% of nominal.
2868.2010.01.1.0
www.analogictech.com
5
www.DataSheet.in
5 Page 
PRODUCT DATASHEET
AAT2868
SystemPowerTM CABC Compatible 4 Channel Backlight Driver with Dual LDO Regulators
Typical Characteristics
Dropout Characteristics
(VOUTA = 2.8V)
3.4
IOUT = 0mA
3.2 IOUT = 10mA
IOUT = 50mA
IOUT = 100mA
3.0 IOUT = 150mA
IOUT = 200mA
2.8
2.6
2.4
2.7
2.8 2.9
3.0 3.1
Input Voltage (V)
3.2
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.7
Dropout Characteristics
(VOUTA = 3.0V)
IOUT = 0mA
IOUT = 10mA
IOUT = 50mA
IOUT = 100mA
IOUT = 150mA
IOUT = 200mA
2.8 2.9
3.0 3.1
Input Voltage (V)
3.2
PSRR vs. Frequency
(VIN = 3.6V, VRIPPLE = 500mVPP, CIN = COUT = 2.2μF, IL = 10mA)
100
80
60
40
20
0
0.1 1 10 100
Frequency (KHz)
2868.2010.01.1.0
www.DataSheet.in
www.analogictech.com
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| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet AAT2868.PDF ] | |
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