AL3157 Datasheet, PDF (1/9 Pages) Diodes Incorporated – HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER FOR SMALL SCREEN BACKLIGHTING

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
C_N ³
V_IN
4
C_P ⁵
V_OUT 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
V_IN
2.2µF
C_IN
1µF
C₁
EN1
EN2
4
V_IN
Flash/
Light
(EN1)
5
C_P
3
C_N
11
EN1
1
EN2
AL3157
6
V_OUT
12
D1
10
D2
D3 ⁸
D4 ⁷
PGND GND
2
9
Backlight
(EN2)
2.2µF
C_OUT
AL3157
Document number: DS35116 Rev. 1 - 2
1 of 9
www.diodes.com
March 2011
© Diodes Incorporated