LM3433 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – Common Anode Capable High Brightness LED Driver with High Frequency Dimming

November 26, 2007
LM3433
Common Anode Capable High Brightness LED Driver with
High Frequency Dimming
General Description
The LM3433 is an adaptive constant on-time DC/DC buck
(step-down) constant current controller (a true current
source). The LM3433 provides a constant current for illumi-
nating high power LEDs. The output configuration allows the
anodes of multiple LEDs to be tied directly to the ground ref-
erenced chassis for maximum heat sink efficacy. The high
frequency capable architecture allows the use of small exter-
nal passive components and no output capacitor while main-
taining low LED ripple current. Two control inputs are used to
modulate LED brightness. An analog current control input is
provided so the LM3433 can be adjusted to compensate for
LED manufacturing variations and/or color temperature cor-
rection. The other input is a logic level PWM control of LED
current. The PWM functions by shorting out the LED with a
parallel switch allowing high PWM dimming frequencies. High
frequency PWM dimming allows digital color temperature
control, interference blanking, field sequential illumination,
and brightness control. Additional features include thermal
shutdown, V_CC under-voltage lockout, and logic level shut-
down mode. The LM3433 is available in a low profile LLP-24
package.
Features
■ ^{Operating input voltage range of -9V to -14V w.r.t. LED}
anode
■ ^{Control inputs are referenced to the LED anode}
■ ^{Output current greater than 6A}
■ ^{Greater than 30kHz PWM frequency capable}
■ ^{Negative output voltage capability allows LED anode to be}
tied directly to chassis for maximum heat sink efficacy
■ ^{No output capacitor required}
■ ^{Up to 1MHz switching frequency}
■ ^{Low I}_Q^{, 1mA typical}
■ ^{Soft start}
■ ^{Adaptive programmable ON time allows for constant ripple}
current
■ ^{LLP-24 package}
Applications
■ ^{LCD backlighting}
■ ^{Projection systems}
■ ^{Solid state lighting}
■ ^{Automotive lighting}
Typical Application Circuit
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