LM3508 Datasheet, PDF (1/20 Pages) National Semiconductor (TI) – Synchronous Magnetic Constant Current White LED Driver

LM3508
www.ti.com
SNVS494C – APRIL 2007 – REVISED MAY 2013
LM3508 Synchronous Magnetic Constant Current White LED Driver
Check for Samples: LM3508
FEATURES
1
•2 Drives 4 Series White LEDs with up to 30mA
• >80% Peak Efficiency
• Up to 100kHz PWM Brightness Control
• Accurate ±5% LED Current Regulation across
V_IN range
• Internal Synchronous PFET (No Schottky
Diode Required)
• True Shutdown Isolation
• Output Short-Circuit Protection
• 17.5V Over-Voltage Protection
• Internal Soft-Start Eliminates Inrush Current
• Wide Input Voltage Range: 2.7V to 5.5V
• 850kHz Fixed Frequency Operation
• Low Profile 9-Bump DSBGA Package
(1.514mm x 1.514mm x 0.6mm)
DESCRIPTION
The LM3508 is a synchronous boost converter (no
external Schottky diode required) that provides a
constant current output. It is designed to drive up to 4
series white LEDs at 30mA from a single-cell Li-Ion
battery. A single low power external resistor is used
to set the maximum LED current. The LED current
can be adjusted by applying a PWM signal of up to
100kHz to the DIM pin. Internal soft-start circuitry is
designed to eliminate high in-rush current at start-up.
For maximum safety, the device features an
advanced short-circuit protection when the output is
shorted to ground. Additionally, over-voltage
protection and an 850kHz switching frequency allow
for the use of small, low-cost output capacitors with
lower voltage ratings. During shutdown, the output is
disconnected from the input preventing a leakage
current path through the LEDs to ground. The
LM3508 is available in a tiny 9-bump chip-scale
DSBGA package.
APPLICATIONS
• White LED Backlighting
• Handheld Devices
• Digital Cameras
• Portable Applications
Typical Application Circuit
22 PH
2.7V to 5.5V
1 PF
SW
IN
OUT
1 PF
LM3508
EN
ILED
PWM Input
DIM
AGND
SET
PGND
R_SET
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007–2013, Texas Instruments Incorporated