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PDF AAT2803 Data sheet ( Hoja de datos )
| Número de pieza | AAT2803 | |
| Descripción | Six-Channel White LED Backlight Charge Pump | |
| Fabricantes | AAT | |
| Logotipo |  |
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AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
General Description
Features
ChargePump™
The AAT2803 is a dual charge pump designed to sup-
port both white LED backlight and flash applications
• VIN Range: 2.7V to 5.5V
• Dual Charge Pump:
for systems operating with lithium-ion/polymer batter-
— Flash: Charge Pump Doubler
ies. The backlight charge pump is capable of driving
— Backlight: Tri-Mode Charge Pump
up to six LEDs at a total of 180mA. The current sinks
• Backlight Charge Pump:
may be operated in group or in parallel for driving
— Programmable Current With Single GPIO
higher current LEDs. To maximize power efficiency,
— 16 Current Steps
the charge pump operates in 1X, 1.5X, or 2X mode,
— 15/20/30mA Max Current
where the mode of operation is automatically select-
— Four Low Current Settings
ed by comparing the forward voltage of each LED
— Individual Main/Sub-Group Control
with the input voltage. AnalogicTech's AS2Cwire™
(Advanced Simple Serial Control™) serial digital input
— Low IQ (50μA) for Low-Current Mode
— Drives Six Channels of LEDs
is used to enable, disable, and set current for each
• Flash Charge Pump:
LED with a 16-level logarithmic scale plus four low-
current settings down to 50μA for optimized efficien-
— Regulated VOUT_FL 4.5/5.0 Volts
— Up to 300mA of Current for Flash
cy, with a low housekeeping current of only 50μA.
• 1MHz Constant Switching Frequency
The flash charge pump is a charge pump doubler
with a regulated output voltage. It is designed to
deliver 120mA of continuous current and up to
300mA of pulsed current. It has an independent
enable pin for improved power savings.
• Independent Backlight/Flash Control
• Built-In Thermal Protection
• Built-In Auto-Disable for Open Circuit
• Automatic Soft Start
• IQ <1μA in Shutdown
• Available in QFN44-24 Package
The AAT2803 is equipped with built-in protectwiwown.D,ataSheet4U.com
short-circuit, and auto-disable for load short-circuit
condition. Built-in soft-start circuitry prevents exces-
sive inrush current during start-up. A low-current
shutdown feature disconnects the load from VIN and
reduces quiescent current to less than 1μA.
The AAT2803 is available in a Pb-free, space-saving,
thermally enhanced 24-pin 4x4mm QFN package
and is rated over the -40°C to +85°C temperature
range.
Applications
• Color (RGB) Lighting
• Programmable Current Sink
• White LED Backlighting
• White Photo Flash for Digital Still Cameras
Typical Application
C1 C2
1μF 1μF
C3
1μF
C1+ C1- C2+ C2- C3+ C3-
VIN VOUT
VIN CIN
1μF
AAT2803
EN_FL
EN/SET
ENFL
EN/SET
GND
D6
D5
D4
D3
D2
D1
Flash
COUT
1μF
Backlight
D6 D5 D4 D3 D2 D1
COUT
1μF
2803.2006.04.1.5
1
1 page  
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
Electrical Characteristics1
VIN = 3.6V, CIN = COUT = C1 = C2 = C3 = 1.0μF; TA = -40°C to +85°C, unless otherwise noted.
Typical values are TA = 25°C.
Symbol
TEN/SET LO
TEN/SET_HI_MIN
TEN/SET_HI_MAX
TOFF
TLAT
IEN/SET;EN_FL
Description
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
Input Leakage
Conditions
VEN/SET;EN_FL = 5V; VIN = 5V
Min Typ Max Units
0.3 75
50
75
μs
ns
μs
500 μs
500 μs
-1.0 1.0 μA
1. The AAT2803 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2803.2006.04.1.5
5
5 Page 
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
Functional Block Diagram
EN_FL
Soft-Start
1MHz
Oscillator
C1+ C1-
2X
Charge Pump
VIN
EN/SET
AS 2Cwire
Interface
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
1X
1.5X
2X
Charge
Pump
6 x 16 bit
ROM
6 x 16 bit
ROM
VREF
D/A
D/A
D/A
D/A
D/A
D/A
VOUT_FL
C2 +
C2 -
C3 +
C3 -
VOUT_BL
D1
D2
D3
D4
D5
D6
GND
Functional Description
The AAT2803 is a dual charge pump targeted for
backlight and flash applications. The charge pump
for white LED applications is a tri-mode load switch
(1X) and high efficiency (1.5X or 2X) charge pump
device. To maximize power conversion efficiency,
an internal sensing circuit monitors the voltage
required on each constant current sink input and
sets the load switch and charge pump modes based
on the input battery voltage and the current sink
input voltage. As the battery discharges over time,
the backlight charge pump is enabled when any of
the six current sink inputs near dropout. The charge
pump initially starts in 1.5X mode. If the charge
pump output drops enough for any current source
output to become close to dropout, the charge pump
will automatically transition to 2X mode.
For flash applications, charge pump doubler archi-
tecture is used to support the high current demand
required by the application. Charge pump regula-
tion is achieved by sensing the output voltage
2803.2006.04.1.5
through an internal resistor divider network. A
switch doubling circuit is enabled when the divided
output drops below a preset trip point controlled by
an internal comparator. The free-running charge
pump switching frequency is approximately 1MHz.
The charge pump is designed to deliver 120mA of
continuous current and 300mA of pulsed current.
The AAT2803 requires only six external compo-
nents: three 1μF ceramic capacitors for the charge
pump flying capacitors (C1, C2, and C3), one 1μF
ceramic input capacitor (CIN), one 0.33μF to 1μF
ceramic capacitor for the backlight charge pump
output, and one 1μF for the flash charge pump out-
put. The six constant current sink inputs (D1 to D6)
can drive six individual LEDs with a maximum cur-
rent of 30mA each. The unused sink inputs must be
connected to VOUT_BL, otherwise the part will operate
only in 2X charge pump mode. The AS2Cwire serial
interface enables the backlight charge pump and
sets the current sink magnitudes. AS2Cwire
addressing allows independent control of two
groups of current sink input: D1 to D4 and D5 to D6.
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AAT2803.PDF ] | |
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