LM3431_08 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – 3-Channel Constant Current LED Driver with Integrated Boost Controller

January 8, 2008
LM3431/LM3431A
3-Channel Constant Current LED Driver with Integrated
Boost Controller
General Description
The LM3431 is a 3-channel linear current controller combined
with a boost switching controller ideal for driving LED back-
light panels in space critical applications. The LM3431 drives
3 external NPN transistors or MOSFETs to deliver high ac-
curacy constant current to 3 LED strings. Output current is
adjustable to drive strings in excess of 200 mA. The LM3431
can be expanded to drive as many as 6 LED strings.
The boost controller drives an external NFET switch for step-
up regulation from input voltages between 5V and 36V. The
LM3431 features LED cathode feedback to minimize regula-
tor headroom and optimize efficiency.
A DIM input pin controls LED brightness from analog or digital
control signals. Dimming frequencies up to 25 kHz are pos-
sible with a contrast ratio of 100:1. Contrast ratios greater than
1000:1 are possible at lower dimming frequencies.
The LM3431 eliminates audible noise problems by maintain-
ing constant output voltage regulation during LED dimming.
Additional features include LED short and open protection,
fault delay/error flag, cycle by cycle current limit, and thermal
shutdown for both the IC and LED array. The enhanced
LM3431A features reduced offset voltge for higher accuracy
LED current.
Features
■ ^{3-channel programmable LED current}
■ ^{High accuracy linear current regulation}
■ ^{Analog and digital PWM dimming control}
■ ^{Up to 25kHz dimming frequency}
■ ^{>100:1 contrast ratio}
■ ^{Integrated Boost controller}
■ ^{5V-36V input voltage range}
■ ^{Adjustable switching frequency up to 1MHz}
■ ^{LED short and open protection}
■ ^{Selectable fault shutdown or automatic restart}
■ ^{Programmable fault delay}
■ ^{Programmable cycle by cycle current limit}
■ ^{Output Over Voltage Protection}
■ ^{No Audible Noise}
■ ^{Enable pin}
■ ^{LED Over-Temperature shutdown input}
■ ^{Thermal Shutdown}
■ ^{TSSOP-28 exposed pad package}
Applications
■ ^{Automotive Infotainment Displays}
■ ^{Small to Medium Format Displays}
Typical Application Circuit
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