Diodes AL3157 User Manual
Al3157, Ne w produc t description, Pin assignments
AL3157
HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER
FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT
AL3157
Document number: DS35116 Rev. 1 - 2
1 of 9
March 2011
© Diodes Incorporated
N
E
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PRODUC
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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 V
IN
and V
OUT
) 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 V
OUT
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 V
IN
to reduce
quiescent current less than 1µA.
The AL3157 is available in a lead-free, space-saving
thermally enhanced 12-pin 3x3mm DFN package.
Pin Assignments
V
IN
V
OUT
C
N
D4
C
P
D1
D2
EN1
7
6
5
4
3
2
1
10
11
12
9
8
PGND
EN2
Exposed Pad
( Top View )
D3
GND
U-DFN3030-12
Features
• 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
•
V
IN
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 V
OUT
short circuit
Protection
•
Soft Start for reducing in-rush current
•
I
Q
<1µA in Shutdown
• Thermally-Enhanced
DFN3030-12
Package:
Available in “Green” Molding Compound (No Br, Sb)
•
Lead Free Finish/ RoHS Compliant (Note 1)
Applications
•
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
Typical Application Circuit
AL3157
V
OUT
D1
D2
D3
D4
EN2
EN1
EN2
EN1
2.2µF
C
IN
V
IN
V
IN
1µF
C
1
C
P
C
N
5
3
6
12
10
8
7
1
11
4
PGND
GND
2
9
2.2µF
C
OUT
Flash/
Light
(EN1)
Backlight
(EN2)
AL3157
V
OUT
D1
D2
D3
D4
EN2
EN1
EN2
EN1
2.2µF
C
IN
V
IN
V
IN
1µF
C
1
C
P
C
N
5
3
6
12
10
8
7
1
11
4
PGND
GND
2
9
2.2µF
C
OUT
Flash/
Light
(EN1)
Backlight
(EN2)