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 illuminating high power LEDs. The output configuration allows the anodes of multiple LEDs to be tied directly to the ground referenced chassis for maximum heat sink efficacy. The high frequency capable architecture allows the use of small external passive components and no output capacitor while maintaining 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 correction. 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, VCC under-voltage lockout, and logic level shutdown mode. The LM3433 is available in a low profile 24-pin WQFN package.

• Operating Input Voltage Range of -9V to -14V w.r.t. LED Anode
• Control Inputs 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 IQ, 1mA Typical
• Soft Start
• Adaptive Programmable ON Time Allows for Constant Ripple Current
• 24-pin WQFN Package