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PDF AAT2869 Data sheet ( Hoja de datos )
| Número de pieza | AAT2869 | |
| Descripción | constant-frequency charge pump DC/DC converter | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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SystemPowerTM
PRODUCT DATASHEET
AAT2869
Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs
General Description
The AAT2869 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
efficiency for white LED applications. The AAT2869 is
capable of driving 4 white LEDs at a total of 124mA from
a 2.7V to 5.5V input. The current sinks may be operated
individually or in parallel for driving higher-current LEDs.
A low external parts count (two 1μF flying capacitors and
two small 1μF capacitors at IN and OUTCP) makes the
AAT2869 ideally suited for small battery-powered appli-
cations. The fade-in/fade-out feature makes backlight
turn-on/turn-off more visual comfortable. The AAT2869
also includes two 150mA low, drop-out 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, to enable/disable the LDOs, and to
set the LDO's output. The programmable LED current
ranges from 31mA to 0.4mA.
Each output of the AAT2869 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 AAT2869 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
• Fade In and Fade Out
• 0.9MHz Constant Frequency
• Automatic Soft-Start Limits Inrush Current
• Dual 150mA LDOs
▪ Five Voltages with 1.2V, 1.5V, 1.8V, 2.8V, and 3.0V,
Sixteen Combinations Set by AS2Cwire
▪ Enable Control Independently by AS2Cwire
▪ 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 (DSCs)
• LED Photo Flash/Torch
• MP3 Players
• PDAs and Notebook PCs
• Smartphones
Typical Application
VIN
2.7~5.5V
C1
1μF
CIN
2.2μF
AS2Cwire
CF
1μF
C1+ C2+
C1- C2-
IN OUTCP
INLDO
AAT2869
EN/SET
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
2869.2010.01.1.0
www.DataSheet.in
www.analogictech.com
1
1 page  
SystemPowerTM
PRODUCT DATASHEET
AAT2869
Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs
Typical Characteristics
CP Operating Current vs. Input Voltage
(1x Mode)
0.6
0.5
0.4
0.3
0.2
85°C
0.1 25°C
-40°C
0.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
CP Operating Current vs. Input Voltage
(1.5x Mode)
3.0
2.5
2.0
1.5
1.0
85°C
0.5 25°C
-40°C
0.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
CP Input Current vs. Input Voltage
200
VF = 3.3V, ILED = 31mA
VF = 3.2V, ILED = 20mA
160 VF = 3.1V, ILED = 10mA
VF = 2.9V, ILED = 5mA
120
80
40
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Shutdown Current vs. Temperature
0.10
0.08
0.06
0.04
0.02
0.00
-40
VIN = 3.6V
VIN = 5.5V
-15 10
35 60
Temperature (°C)
85
LDO Operating Current vs. Input Voltage
(LDOA + LDOB)
0.25
0.20
0.15
0.10
0.05 85°C
25°C
-40°C
0.00
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
LDO Operating Current vs. Input Voltage
(LDOA Only)
0.25
0.20
0.15
0.10
0.05 85°C
25°C
-40°C
0.00
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
2869.2010.01.1.0
www.DataSheet.in
www.analogictech.com
5
5 Page 
SystemPowerTM
PRODUCT DATASHEET
AAT2869
Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs
Functional Block Diagram
IN
C1+
C1-
C2+
C2-
FCAP
EN/SET
INLDO
Dual-mode
Charge Pump
1X/1.5X
4
Fade Filter
32-step AS2Cwire
Backlight Control
and LDO Setting
Control
Logic
OUTCP
D1
D2
D3
D4
LDOA
LDOB
GND AGND
Functional Description
The AAT2869 is a high efficiency charge pump white LED
driver for portable applications. It can drive up to 4 white
LEDs. The two integrated LDOs can provide 1.2V, 1.5V,
1.8V, 2.8V and 3.0V output voltages in 16 combinations
with up to 150mA load capability.
The AAT2869's charge pump is a fractional charge pump
and can multiply the input voltage by 1 or 1.5 times. The
charge pump switches at a fixed frequency of 0.9MHz.
The internal mode-selection circuit automatically switch-
es the mode between 1x and 1.5x based on the input
voltage, white LED forward voltage VF, and the pro-
grammed LED current. This mode switching maximizes
the efficiency throughout the entire LED load range.
When the input voltage is high enough, the charge pump
operates in 1x mode (no charge pump) to provide max-
imum efficiency. If the input voltage is too low to supply
the programmed LED current, typically when the battery
discharges and the voltage decays, the 1.5x charge
pump mode is automatically enabled. When the battery
is connected to a charger and the input voltage rises suf-
ficiently, the device will switch back to 1x mode.
Six registers are designed for charge pump enable/dis-
able control, LED current programming, fade-in, fade-
out enable/disable, two LDOs enable/disable control and
LDO output voltage combination setting through the
AS2Cwire interface. After writing address 3, the LED cur-
rent value is programmed by the EN/SET serial data
AS2Cwire interface. The AS2Cwire interface records rising
edges of the EN/SET pin and decodes them into 32 indi-
vidual current level settings from 0.4mA to 31mA. To get
a visual fade in and fade out effect, a small external
capacitor is used to set LED current rising exponentially
to the programmed value and decreasing exponentially
to the programmed floor LED current level.
The AAT2869 has five registers with up to four bits each
to control LED backlighting enable/disable, LED current,
enable/disable for the two LDOs, output voltages, etc. as
shown in Table 1. Each data register can be written with
1 to 16 EN/SET rising edges. Some bits are internally
reserved and should only be written with data 0, such as
address 0, bit D0, D1 and D3, etc. in order to avoid
unexpected results. Address 0 is the default address.If
EN/SET is pulled high after a low level lasting for at least
2869.2010.01.1.0
www.analogictech.com
11
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AAT2869.PDF ] | |
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