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ADP8140 Analog dimming

Question asked by Risto.T on Jul 12, 2018
Latest reply on Jul 17, 2018 by Risto.T

Hi,

 

I am using ADP8140 for driver of two string of white led. Both string has different light color so I'm using FET for controlling bot lines so that I can shut down or light up any string I want. I have DAC connected to DIM pin for adjust LED current. I have two LED string, each string has parallel 4+4 LED. I'm feeding LED straight from my power supply, +24V. 

 

Here is my current schematics.

I already add PU for FAULT as I was missing that and also route EN to VREG.

At COMP, I have RC network, C10 0.47uF and R9 1K. 

When I turn on my power +24, led light up immediately and driver start to sink current as much as Rset (R11) resistor allow. Changing voltage at DIM pin does not effect at all.

 

Any Idea, what is wrong at my design?

 

-Risto

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