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 LLP-24
package.