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AL3157

HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER


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AL3157 pdf
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Description
The AL3157 is a low noise, constant frequency charge
pump DC/DC converter that uses a Dual mode load switch
(1x), and doubling (2x) conversion for driving white LEDs.
Low external part count (one 1µF flying capacitor and two
2.2µF capacitors at VIN and VOUT) make this part ideally
suited for small, battery-powered applications
The AL3157 drives 3 channels at up to 30mA for small
screen backlighting and an additional channel up to 210mA
for LED Flash or LED Flashlight – All from a 2.7V to 5.5V
input.
The AL3157 uses two control inputs (EN1/2) to
enable/disable it and PWM dim the LED current. EN2
controls/PWM dims the backlight LEDs at 30mA per
channel and EN1 controls/PWM dims the Flash/Flashlight
LEDs at 210mA.
Each output is equipped with built-in protection for VOUT
short circuit and auto-disable for LED failure conditions.
Built-in soft-start circuitry prevents excessive in-rush
current during start-up and mode switching. A low-current
shutdown feature disconnects the load from VIN to reduce
quiescent current less than 1µA.
The AL3157 is available in a lead-free, space-saving
thermally enhanced 12-pin 3x3mm DFN package.
Features
Pin Assignments
( Top View )
EN2 1
PGND 2
CN 3
VIN
CP
VOUT
4
5
6
Exposed Pad
12 D1
11 EN1
10 D2
9 GND
8 D3
7 D4
U-DFN3030-12
Applications
Dual-Mode 1x and 2x Charge Pump
Up to 300mA drive capability
o 3-channel for backlight – 30mA/ch
o 1-channel for Flight/light – 210mA
VIN Range: 2.7V to 5.5V
Two simple PWM dimming control inputs up to
50kHz
1.2 MHz Constant Switching Frequency
Built-In Thermal, Open-Circuit and VOUT short circuit
Protection
Soft Start for reducing in-rush current
IQ <1µA in Shutdown
Thermally-Enhanced DFN3030-12 Package:
Available in “Green” Molding Compound (No Br, Sb)
Lead Free Finish/ RoHS Compliant (Note 1)
Smart Touch Phone LED Backlighting
PDA White LED backlighting
Backlighting + Torch light
Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at
http://www.diodes.com/products/lead_free.html
Typical Application Circuit
VIN
2.2µF
CIN
1µF
C1
EN1
EN2
4
VIN
Flash/
Light
(EN1)
5
CP
3
CN
11
EN1
1
EN2
AL3157
6
VOUT
12
D1
10
D2
D3 8
D4 7
PGND GND
29
Backlight
(EN2)
2.2µF
COUT
AL3157
Document number: DS35116 Rev. 1 - 2
1 of 9
www.diodes.com
March 2011
© Diodes Incorporated



No Preview Available !

AL3157 pdf
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
Pin Descriptions
Pin Name
EN2
PGND
CN
VIN
CP
VOUT
D4
D3
GND
D2
EN1
D1
EP
Pin Number
Description
1 Enable Pin 2: Controls outputs D2, D3 and D4
2 Charge Pump Switch Ground: Connect to GND
3 Negative Terminal of Flying Capacitor
4 Input Power Supply. Decouple with a 2.2µF capacitor between this pin and ground.
5 Positive Terminal of Flying Capacitor
Charge pump output to drive D1~D4 load circuit. Decouple with a 2.2µF capacitor between
6 this pin and ground.
7 Current sink input #4. Drive up to 30mA LED current. Connect to VOUT when un-used.
8 Current sink input #3. Drive up to 30mA LED current. Connect to VOUT when un-used.
9 Ground
10 Current sink input #2. Drive up to 30mA LED current. Connect to VOUT when un-used.
11 Enable Pin 1: Controls output D1
12 Current sink input #1. Drive up to 210mA LED current. Connect to VOUT when un-used.
EP PAD Exposed Pad (bottom). Connect to GND directly underneath the package.
Functional Block Diagram
CN CP
VIN
EN1
EN2
CHARGE PUMP
SWITCHES
SHORT
CIRCUIT
PROTECTION
DIGITAL CONTROL BLOCK
BANDGAP
OSCILLATOR
OVER
TEMPERATURE
PROTECTION
UNDER
VOLTAGE
LOCKOUT
CURRENT
CONTROL
OVER
VOLTAGE
PROTECTION
VOUT
D1
D2
D3
D4
GND
AL3157
Document number: DS35116 Rev. 1 - 2
2 of 9
www.diodes.com
March 2011
© Diodes Incorporated



Part Number AL3157
Description HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
Maker Diodes - Diodes
Total Page 9 Pages
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