AAT2842
High-Current Charge Pump with S
2
Cwire™
Control and Dual LDO for Backlight and Flash
General Description
The AAT2842 is a highly integrated charge pump
with dual linear regulators optimized for systems
operating with lithium-ion/polymer batteries. The
charge pump provides power for both white LED
backlight/keypad and flash. Up to four backlight
LEDs can be driven at up to 30mA each and key-
pad LEDs can be driven using lower currents set by
the S
2
Cwire interface. In addition, up to four flash
LEDs can be driven with up to 600mA total. Two
separate S
2
Cwire™ (Simple Serial Control™) serial
digital interfaces are used to enable, disable, and
set the current to one of 16 levels for both backlight
and flash LEDs. Backlight/keypad and flash current
settings are also controlled through external resis-
tors for increased versatility with reduced accuracy
and matching. Backlight/keypad current matching
is 1% for uniform display brightness, and flash cur-
rent matching is 4% for uniform power dissipation.
An internal flash timer set by an external capacitor
protects the flash LED should a fault occur.
The AAT2842 offers two high-performance
MicroPower™ low dropout (LDO) linear regulators.
A single enable input controls both regulators and
each supplies up to 200mA to the load. Both LDOs
consume only 85µA quiescent current, making
them ideal for battery-operated applications.
The AAT2842 is equipped with built-in short-circuit
and over-temperature protection. The charge pump
soft-start circuitry prevents excessive inrush current
at start-up. The product is available in a Pb-free,
space-saving TQFN44-28 package and operates
over the -40°C to +85°C ambient temperature range.
Features
•
•
ChargePump
™
•
•
•
•
•
V
IN
Range: 2.7V to 5.5V
Tri-Mode Charge Pump:
— Drives up to Four Backlight/Keypad and
Four Flash LEDs
— Separate S
2
Cwire Control for
Backlight/Keypad and Flash Currents
— Backlight/Keypad and Flash Current Set
by Separate External Resistors
— Flash Timer Set with External Capacitor
— Up to 2MHz Switching Frequency
Two Linear Regulators:
— 200mA Output Current
— 200mV Dropout
— Output Voltage Adjustable from 1.2V to
V
BATTERY
— Output Auto-Discharge for Fast Shutdown
— 85µA Quiescent Current
Built-In Thermal Protection
Automatic Soft Start
-40°C to +85°C Temperature Range
Available in 4x4mm TQFN44-28 Package
Applications
•
•
•
Camera-Enabled Mobile Devices
Digital Still Cameras
Multimedia Mobile Phones
Typical Application
C1
1μF
C1+
C2
1μF
C1- C2+
C2-
IN
V
BAT
C
IN
4.7μF
EN_BACKLIGHT
EN_FLASH
OUT
AAT2842
BL1
BL2
BL3
BL4
FL1
FL2
FL3
FL4
OUTA
C
OUT
2.2μF
IN
BENS
FENS
CT
BSET
R
SET1
C
T
R
SET2
C
REF
EN_LDO
V
OUT
LDOA
R
2A
C
OUTA
FSET
REF
FBA
OUTB
ENL
AGND
R
2B
FBB
PGND
R
1B
V
OUT
LDOB
C
OUTB
R
1A
2842.2007.09.1.2
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
