LM3430 datasheet(4/16 Pages) NSC

4 / 16 page

Configuration of the Demonstration Board for Evaluation

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Analog PWM Dimming Mode

•

Leave jumper JP3 open to enable the Analog Dimming

Mode;

•

Short pins 1-2 of jumper JP5 to select the Analog control

input;

•

The VR1 is used to derive the analog control voltage from

LM3432's VCC output (5V nominal) and pass to LM3432's

DIM input pin to control the dimming of the LED;

•

Adjust VR5 to change the LED brightness. The ON current

of the LED is still maintained, only the duty ratio of ON time

is adjusted to achieve the effect of dimming. This ensures

the correct color is preserved even in dimmed output

conditions.

Digital PWM Dimming Mode

•

Short jumper JP3 to enable the Digital Dimming Mode;

•

Short pins 2-3 of jumper JP5 to select the Digital control

input;

•

The external PWM dimming control signal applied to CN2

is then routed to LM3432's DIM input pin;

•

The control of LED current ON-OFF is passed to the

externally applied PWM dimming control signal. The ON

duty of the PWM control signal governs the LED

brightness.

LM3430 Datasheet(PDF) 4 Page - National Semiconductor (TI)