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A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
DESCRIPTION
FEATURES
The A8440 is a complete backlight display solution that is
designed to independently control LEDs. The A8440 is
a charge pump WLED driver capable of driving up to 4
LEDs with 30mA each LED. Its four tightly regulated
current sources ensure excellent LED current and
brightness matching. LED driver current is programmed
by an external resistor.
The A8440 operates over an input voltage range from 3V
to 5.5V, optimized for WLED applications powered by
Li-Ion battery, requiring only for low cost ceramic
capacitors.
The A8440 provides excellent efficiency by operating the
charge pump in a gain of 1 or 1.5. Maximum efficiency
is achieved over Li-Ion battery voltage range by selecting
the proper gain based on the LED forward voltage
requirements.
The A8440 has a fixed 1MHz switching frequency,
consuming less than 1uA of supply current when
shutdown.
The A8440 LED dimming can be accomplished by
several methods including using a DC voltage to set the
RSET pin current, applying a PW signal on the control
signals, or adding a switched resistor in parallel with
RSET. The enable input pin allows the A8440 to be
placed in power-down mode.
The A8440 is available in 16pin TQFN (3x3mm)
(4x4mm) package.
QFN16
Typical Application
Individually Current Regulation for Up to 4
LEDs with a Typical Tolerance of 5%
Input Voltage Range: 3V to 5.5V
Wide Current Range, up to 30mA per LED
3-bit Digital Output Control
3%Typical Tolerance Current Matching
1x and 1.5x mode Operating with Automatic
Switchover
High Available Total LED Current 120mA (4
x 30mA)
Peak Efficiency Over 91%
Fixed Frequency 1MHz
Power-Saving Shutdown mode of 1uA
Open LED Protection
Soft-Start Over-Current-Protection and
Current Limiting
Available in TQFN-16 (3x3mm) and QFN16
(4x4mm) Package
APPLICATION
Portable Devices, Mobile Phone, DVR,
Smart Phone...etc.
Hand-held Devices, PDA, PMP, MP3,
DSC...etc.
White LED Backlight Application
LED Modules
ORDERING INFORMATION
Package Type
Part Number
TQFN16(3x3mm)
TQ16
QFN16 (4x4mm)
Q16
A8440TQ16R
A8440TQ16VR
A8440Q16R
A8440Q16VR
R: Tape & Reel
Note
V: Green Package
AiT provides all Pb free products
Suffix “ V “ means Green Package
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-1-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
PIN DESCRIPTION
Top View
Top View
Pin #
Pin Name
1
EN
2
CTR0
Digital Control Input 0
3
CTR1
Digital Control Input 1
4
CTR2
Digital Control Input 2
5
RSET
Set LED Output Current by the Current Sourced out of the RSET pin
6
VOUT
Output Pin, Charge Pump output connected to the LED anodes
7
VIN
Input Pin, Supply Voltage
8
C1+
Bucket Capacitor 1 Terminal
9
C1-
Bucket Capacitor 1 Terminal
10
C2-
Bucket Capacitor 2 Terminal
11
C2+
Bucket Capacitor 2 Terminal
12
GND
Ground Pin
13
LED4
LED4 Cathode Terminal
14
LED3
LED3 Cathode Terminal
15
LED2
LED2 Cathode Terminal
16
LED1
LED1 Cathode Terminal
REV1.2
Function
Enable Input Active High
- JAN 2007 RELEASED – JUN 2008 REVISED -
-2-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
ABSOLUTE MAXIMUM RATINGS
VIN, LEDx, VOUT Voltage
-0.3V ~ 7.0V
EN, CTRx Voltage
-0.3V ~ VIN (V)
RSET Voltage
-0.3V ~ VIN (V)
RSET Current
±1mA
Storage Temperature Range
Lead Temperature (Soldering, 10s)
Operating Temperature Range
-65oC ~ +150oC
+300oC
-40oC ~ +85oC
ESD Ratings
Human Body Model (HBM)
Machine Model (MM) (Note1)
ILED per LED pin
Thermal Resistance (Junction to Ambient) (θJA)
Power Dissipation (PD=@TA=25oC)
2kV
200V
0 to 30uA
68oC/W
1.47W
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 .
Note1: Machine models are with 200pF capacitor discharged directly into each pin.
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-3-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
ELECTRICAL CHARACTERISTICS
VIN=3.5V, TA=25oC, IRSET=5uA, unless otherwise specified.
Parameter
VIN at mode Transition
Symbol
VIN-Transition
from 1x to 1.5x
RSET Regulated Voltage
Programmed LED Current
ILED
ILED-ACC
LED Channel Matching
ILED-DEV
Output Resistance (Open Loop)
Charge Pump Frequency
1x to 1.5x Mode
Iq
ROUT
Min
Typ
ILED=15mA
3.45
ILED=20mA
3.60
VRSET
LED Current Accuracy
Quiescent Current
Conditions
1.19
1.23
Max
Unit
V
1.24
V
ISET = 6uA
2.5
mA
ISET=41uA
15.0
mA
ISET=83uA
30.0
mA
0.6
%
(ILED - ILEDAVG) / ILEDAVG
3
%
VEN=0V Shutdown Mode
0.05
1
uA
1x Mode, No Load
0.5
1
mA
1.5x Mode, No Load
2.5
5
mA
1x Mode, IOUT=100mA
1.7
Ω
1.5x Mode, IOUT=100mA
4.3
Ω
1.0
MHz
fOSC
TDROPOUT
0.4
0.6
0.9
ms
0.001
1
uA
Transition Dropout Delay
Input Leakage Current
IEN-CTR
ON Inputs EN, CTR0,
1&2
Detect Threshold
VEN-CTR
On Inputs EN,
High
CTR0, 1 & 2
Low
Input Current Limit
ISC
VOUT=GND
Maximum Input Current
ILIM
VOUT>1V
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
0.8
V
0.7
V
30
45
60
mA
200
400
600
mA
-4-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
TYPICAL PERFORMANCE CHARACTERISTICS
VIN=3.6V, EN=VIN, TA=25oC, RSET=24KΩ, CIN=COUT=1uF, unless otherwise specified.
1. Input Current vs. PWM Duty Cycle
4LEDs @60mA, 100Hz PWM Duty Cycle
LEDs @60mA, 1KHz PWM Duty Cycle
2. LED Current vs. Input Voltage
3. Supply Current vs. Input Voltage
4LEDs @60mA
4. LED Cathode Voltage vs. Input Voltage
1LED @15mA
5. Output Voltage vs. Input Voltage
1LED @15mA
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-5-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
6. Efficiency vs. Line Voltage
4LEDs @60mA
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
4LEDs @80mA
7. Efficiency vs. Total LED Current (4LEDs)
8. Efficiency vs. Input Voltage
4LEDs
9. Efficiency vs. Line Voltage
4LEDs @15mA
10. Efficiency vs. Line Voltage
4LEDs @20mA
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-6-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
11. Switching Waveform in 1x Mode
VIN=4.2V, 4LEDs @80mA
12. Switching Waveform in 1.5x Mode
VIN=3.2V, 4LEDs @80mA
13. 1KHz PWM Signal, Vcc=4.2V, 4ILED=60mA
Positive Duty Cycle=30%
PWM Control Enable (CTR0=0, CTR1=1, CTR2=1)
CH1: PWM (DC Decoupling)
CH2: VOUT (DC Decoupling)
CH3: IOUT (AC Decoupling)
14. 1KHz PWM Signal, Vcc=3.2V, 4ILED=60mA
Positive Duty Cycle=30%
PWM Control Enable (CTR0=0, CTR1=1, CTR2=1)
CH1: PWM (DC Decoupling)
CH2: VOUT (DC Decoupling)
CH3: IOUT (AC Decoupling)
15. 100Hz PWM Signal, Vcc=4.2V, 4ILED=60mA
Positive Duty Cycle=40%
PWM Control Enable (CTR0=0, CTR1=1, CTR2=1)
CH1: PWM (DC Decoupling)
CH2: VOUT (DC Decoupling)
CH3: IOUT (AC Decoupling)
16. 100Hz PWM Signal, Vcc=3.2V, 4ILED=60mA
Positive Duty Cycle=30%
PWM Control Enable (CTR0=0, CTR1=1, CTR2=1)
CH1: PWM (DC Decoupling)
CH2: VOUT (DC Decoupling)
CH3: IOUT (AC Decoupling)
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-7-
AiT Semiconductor Inc.
www.ait-ic.com
A8440
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
17. 100Hz PWM Signal, Vcc=3.2V, 4ILED=60mA
Positive Duty Cycle=74%
PWM Control Enable (CTR0=0, CTR1=1, CTR2=1)
CH1: PWM (DC Decoupling)
CH2: VOUT (DC Decoupling)
CH3: IOUT (AC Decoupling)
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-8-
AiT Semiconductor Inc.
www.ait-ic.com
A8440
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
BLOCK DIAGRAM
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
-9-
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
DETAILED INFORMATION
At power-up, the A8440 starts operation in 1x mode. If it is able to drive the programmed LED current, it
continues to operate in 1x mode. If the battery voltage drops to a level where the LED current cannot be met,
the driver automatically switches into 1.5x mode. The 1.5x charge pump will boost the output voltage
accordingly to achieve the nominal LED current.
Typical Circuit
LED Current Setting
The LED current is set by the external resistor RSET connected between the RSET pin and ground.
Various
LED Currents and The associated RSET resistor value for standard 1% precision surface mount resistors:
LED Current (mA)
RSET (KΩ)
1
620
2
234.6
5
90
10
44.2
15
30
20
21.0
30
14.5
Table 1. RSET Resistor Selection
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
- 10 -
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
The digital control lines CTR0, CTR1 and CTR2 allow to turn On or Off a combination of LEDs as below:
Control Lines
LED Outputs
CTR2
CTR1
CTR0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
LED4
LED3
LED2
LED1
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
Table 2. LED Selection
Note: 1 =Logic High (or VIN) ,0 =Logic Low (or GND), - =LED Output OFF
Short Circuit Detect/Disable
The unused LED channels can also be turned off by connecting the respective LED pins to VOUT. In this case,
the corresponding LED driver is disabled and the typical LED sink current is only about 20uA.
When the
following equation is true on any channel, the driver turns off the LED channel:
VOUT – VLED ≤ 1V (LED channel OFF)
Note: The A8440 is designed to drive LEDs with forward voltage greater than 1V and is not compatible with
resistive loads.
PCB Layout
For best performance, a solid ground plane is recommended on the back side of the PCB.
The ground tails
of CIN and COUT should be connected together close to the GND pin of A8440.
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
- 11 -
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
PACKAGE INFORMATION
Dimension in TQFN16 (3x3mm)
REV1.2
(Unit: mm)
- JAN 2007 RELEASED – JUN 2008 REVISED -
Symbol
Min
Nom
Max
A
0.7
0.75
0.80
A1
0.00
0.02
0.05
A3
-
0.20REF
-
D
-
300
-
D2
1.55
1.70
1.80
E
-
3.00
-
E2
1.55
1.70
1.80
e
-
0.50
-
L
0.20
0.30
0.40
K
0.20
-
-
b
0.18
0.25
0.30
- 12 -
A8440
AiT Semiconductor Inc.
www.ait-ic.com
Dimension in QFN16 (4x4mm)
REV1.2
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
(Unit: mm)
- JAN 2007 RELEASED – JUN 2008 REVISED -
Symbol
Min
Nom
Max
A
0.80
0.90
1.00
A1
0.00
0.02
0.05
A3
-
0.20ref
-
D
-
4.00
-
D2
2.00
2.15
2.25
E
-
4.00
-
E2
2.00
2.15
2.25
e
-
0.65
-
L
0.45
0.55
0.65
K
0.20
-
-
b
0.25
0.30
0.35
- 13 -
A8440
AiT Semiconductor Inc.
www.ait-ic.com
4CHANNEL WHITE LED DRIVER
1x /1.5x CHARGE PUMP DISPLAY BACKLIGHT SOLUTION
IMPORTANT NOTICE
AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to
discontinue any integrated circuit product or service without notice, and advises its customers to obtain the
latest version of relevant information to verify, before placing orders, that the information being relied on is
current.
AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to
be suitable for use in life support applications, devices or systems or other critical applications.
products in such applications is understood to be fully at the risk of the customer.
Use of AiT
As used herein may
involve potential risks of death, personal injury, or servere property, or environmental damage.
In order to
minimize risks associated with the customer's applications, the customer should provide adequate design and
operating safeguards.
AiT Semiconductor Inc. assumes to no liability to customer product design or application support.
AiT
warrants the performance of its products of the specifications applicable at the time of sale.
REV1.2
- JAN 2007 RELEASED – JUN 2008 REVISED -
- 14 -