I have an changing input voltage. I would like to feed it into LM3406 and have varying brightness from the Led. So I go through the datasheet.
However,the only information and characteristic of the IC I can understand is that the duty cycle of the output is Vout/Vin when PWM dimming is being applied. I dont know how to obtain desired Vout.
I am not familiar with LEDs. The datasheet tell me high power LEDs can be used. What is high power Led actually. I can find many types of LED on the street and I dont know the compatiblity of each one.
In my case , is it dim pin is not necessary to connect anything? I find that that pin is left open in input voltage comparator for PWM dimming.
Best Answer
The DIM pin is used for PWM dimming from a control signal:
So if you connect a 50% PWM signal to the dim pin, the led connected to the driver is dimmed to 50%.
The VINS pin is used to detect PMW dimming on the Voltage input:
It uses a diode and a capacitor to smooth the input, and allow it to dim that way. See 8.11 for details.
If you want to take a steady but variable voltage input, and dim the led by the range of the input, you would need a circuit to measure the voltage, and produce a PWM signal to the DIM pin. Any common microcontroller should do.