I am assigned with the design of a LED driver with 1 A current and 5 V system power. The customer wants to control all the LEDs with simple switches, nothing digital is involved. So I am thinking of using this LED driver:
http://www.monolithicpower.com/DesktopModules/DocumentManage/API/Document/getDocument?id=66
I thought that if I apply 5V system supply to EN/DIM pin via a switch I can get a constant continuous current(1A). And when the switch is OFF, LED will turn off.
These are diagrams in the datasheet also:
And here is the description for EN/DIM pin:
On/Off Control Input and Dimming Command Input. A voltage greater than 0.7V will turn on
the chip. When the EN/DIM pin voltage (with respect to INGND) rises from 0.7V to 1.4V, the
LED current will change from 0% to 100% of the maximum LED current. To use PWM
dimming, apply a 100Hz to 1kHz square wave signal with amplitude greater than 1.4V to this
pin.
So I am a little confused. I thought Analog dimming was the thing I was up to. However, in pin description, it says apply 100Hz to 1KHz square signal. So question is simple as this. Do I get constant Current for over half hour if I apply constant 5V to EN/DIM pin, or it does not work that way?
Best Answer
Please look at page 8 of the datasheet under "Dimming Control". You can do either PWM or analog dimming. For analog, you vary the EN/DIM pin between 0.7V (0%) and 1.4V (100%). For PWM, you use a 1HKz signal with on > 1.4V and the duty cycle controls the brightness.
You can do it either way.
And to answer your question, putting 5V into EN should give you 1A to the LEDs continuously.