LM3519 Datasheet, PDF (1/20 Pages) National Semiconductor (TI) – High Frequency Boost White LED Driver with High-Speed PWM Brightness Control

LM3519
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SNVS394A – AUGUST 2005 – REVISED SEPTEMBER 2005
LM3519 High Frequency Boost White LED Driver with High-Speed PWM Brightness
Control
Check for Samples: LM3519
FEATURES
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•2 Drives 2 to 4 LEDs at 20mA
• Up to 30kHz PWM Dimming Control Capability
• >80% Peak Efficiency
• Up to 8MHz Switching Frequency
• Small External Components: 1µH -
3.3µH(typ.2.2μH) Inductor and 1µF Output
Capacitor
• True Shutdown Isolation
• Over-Voltage Protection
• Wide Input Voltage Range: 2.7V to 5.5V
• Small Footprint SOT23-6 Package
APPLICATIONS
• LCD, White LED Backlighting on Mobile
Phones
• Digital Still Cameras and PDAs
• General Purpose LED Lighting in Handheld
Devices
DESCRIPTION
The LM3519 drives up to 4 white LEDs with constant current to provide LCD backlighting in handheld devices.
The LED current is internally set to 20mA. The series connection allows the LED current to be identical for
uniform brightness and minimizes the number of traces to the LEDs. Brightness control is achieved by applying a
PWM signal on enable with frequencies up to 30kHz.
The LM3519 features a proprietary PFM regulation architecture with switching frequencies between 2MHz to
8MHz, minimizing inductor size.
Over-voltage protection circuitry and high frequency operation permit the use of low-cost small output capacitors.
During shutdown, the output is disconnected from the input in order to avoid leakage current path through the
LEDs to ground.
The LM3519 is available in a tiny 6-pin SOT23 package.
Typical Application
L
2.2 PH
D
Vout
Vin
Sw
Vin
Cin
Vout
4.7 PF
LM3519
En
Gnd ^LED_rtn
Logic
Voltage
Signal
Input
Cout
1 PF
Vx
Figure 1. Typical Application Circuit
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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 © 2005, Texas Instruments Incorporated