Document
AiT Semiconductor Inc.
www.ait-ic.com
A8442
80mA 4-CHANNEL CHARGE PUMP WHITE LED DRIVER WITH LOW DROPOUT CURRENT SOURCE
DESCRIPTION
FEATURES
The A8442 is a high performance white LED driver. It integrates current sources and automatic mode selection charge pump. The part maintains the high efficiency by utilizing an x1/x1.5 fractional charge pump and low dropout current sources. The small equivalent x1 mode open loop resistance and ultra-low dropout voltage of current source extend the operating time of x1 mode and optimize the efficiency of Li-ion battery in white LED applications.
The A8442 supports up to 4 white LEDs and regulates a constant current for uniform intensity. The part implements a 4-bit DAC for brightness control. Users can easily configure the LED current from 1.25mA to 20mA by a serial pulse. The dimming of white LEDs current can be achieved by applying a pulse signal to the EN pin. There are totally 16 steps of current could be set by users. The operating voltage range is 2.7V to 5.5V. Internal soft start circuitry effectively reduces the in-rush current while both start-up and mode transition. The load is disconnected from VIN while shutdown and the shutdown current is less than 1μA.
90% Average Efficiency Over Battery Life Support up to 4 White LEDs 80mV Typical Current Source Dropout Support up to 80mA Output Current 2% Typical LED Current Accuracy 1% Typical LED Current Matching High Active Soft Start Function Auto Charge Pump Mode Selection 500kHz Fixed Frequency Oscillator Output Over Voltage Protection 16-Step Brightness Control Low Input Noise and EMI Low 1μA Shutdown Current Available in QFN16(3x3) Package
APPLICATION
Mobile Phone, DSC, MP3 White LED Backlighting LCD Display Supply
The A8442 is available in QFN16(3x3) package.
TYPICAL APPLICATION
ORDERING INFORMATION
Package Type
Part Number
QFN16(3x3)
A8442Q16R A8442Q16VR
Note
R: Tape & Reel V: Green Package
AiT provides all Pb free products
Suffix “ V “ means Green Package
REV1.0
-APR 2011 RELEASED -
-1-
AiT Semiconductor Inc.
www.ait-ic.com
PIN DESCRIPTION
A8442
80mA 4-CHANNEL CHARGE PUMP WHITE LED DRIVER WITH LOW DROPOUT CURRENT SOURCE
Pin #
1 2 3 4 5 6 7 8 9,15 10 11 12 13 14 16 Exposed Pad
Symbol
C1N C2N C2P C1P AGND PGND VIN EN NC LED4 LED3 LED2 LED1 VOUT VNG GND
Top View
Function
Negative Terminal of Bucket Capacitor 1 Negative Terminal of Bucket Capacitor 2 Positive Terminal of Bucket Capacitor 2 Positive Terminal of Bucket Capacitor 1 Analog Ground Power Ground Power Input Voltage Chip Enable (Active High), and connects to GPIO pin of MCU No Internal Connection Current Sink For Led4. (If Not In Use ,Pin Should Be Connected To GND) Current Sink For Led3. (If Not In Use ,Pin Should Be Connected To VIN) Current Sink For Led2. (If Not In Use ,Pin Should Be Connected To VIN) Current Sink For Led1. (If Not In Use ,Pin Should Be Connected To VIN) Output Voltage Source for LED1 to LED4 charge pump output exposed pad should be soldered to PCB board and connected to GND
REV1.0
-APR 2011 RELEASED -
-2-
AiT Semiconductor Inc.
www.ait-ic.com
A8442
80mA 4-CHANNEL CHARGE PUMP WHITE LED DRIVER WITH LOW DROPOUT CURRENT SOURCE
ABSOLUTE MAXIMUM RATINGS
Input Voltage
−0.3V to 6V
Output Voltage
−0.3V to 6V
EN Voltage
−0.3V to 6V
Power Dissipation, PD @ TA = 25°C
QFN−16(3X3)
1.47W
Package Thermal Resistance
QFN−16(3x3), θJA
68°C/W
Junction Temperature
150°C
Lead Temperature (Soldering, 10 sec.)
260°C
Junction Temperature Range
−40°C to 125°C
Storage Temperature Range
−65°C to 150°C
ESD Susceptibility
HBM (Human Body Mode)
3kV
MM (Machine Mode)
200V
Stresses above may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated in the Electrical Characteristics are not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
REV1.0
-APR 2011 RELEASED -
-3-
AiT Semiconductor Inc.
www.ait-ic.com
A8442
80mA 4-CHANNEL CHARGE PUMP WHITE LED DRIVER WITH LOW DROPOUT CURRENT SOURCE
ELECTRICAL CHARACTERISTICS
TA = 25°C, Otherwise specified
Parameter
Symbol
Conditions
Min Typ Max
Input Supply Voltage
V IN
2.7 - 5.5
Undervoltage Lockout Threshold
VUVLO
VIN rising or falling
1.8 2.0 2.4
Undervoltage Lockout Hysterresis
- 100 -
Shutdown Current
ISHDN
VIN = 4.2V, EN = LOW
- 1 10
Quiescent of x1 Mode
IQ×1
x1 Mode, VIN = 5.5V, LED off -
1
-
ILED Accuracy
ILED-ERR
2mA < ILED < 20mA
-28
Current Matching
ILED-LED-ERR 2mA < ILED < 30mA
-15
×1 mode to ×1.5 mode Transition voltage(VIN falling)
VLED = 3.4V,
VTRANS
- 3.5 -
ILED1=ILED2=ILED3=ILED4=15mA
Oscillator Frequency
FOSC
VIN-VOUT
- 500K -
Output Over Voltage Protection
VOVP
- 5.5 6
Thermal Shutdown Threshold
- 150 -
Thermal Shutdown Hysteresis
- 10 -
EN Low Time for Shut Down
TSHDN
2- -
EN Low Time for Dimming
TLO.