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I am new in this forum . I had an issue with my newly designed PCB where I use LM3414hv as a constant current driver for led strings. Everything works perfectly except for one thing. When I turn of the main power of my card all leds strings flash briefly. I think its because of the internal pull up of the lm3414hv that activates the driver when pin is HIGH or left open "high impedance". My DC voltage source always shuts down a few seconds after my 5 volt microcontroller when I unplug the main power. The question is How can I force by default this DIM pin at GND when the dim pin is left open 'high impedance state'? Or any other idea to avoid that annoying flashing? Here is the datasheet of LM3414HV and the internal diagram of lm3414 enter image description here Thanks in advance http://www.ti.com/lit/ds/symlink/lm3414.pdf

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  • \$\begingroup\$ have you googled anything about pulling floating pins to ground? \$\endgroup\$ – jsotola May 3 '18 at 22:43
  • \$\begingroup\$ Do you have a 1 µF cap on the VCC pin? \$\endgroup\$ – Misunderstood May 5 '18 at 23:31
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Try putting a 10K resistor from the DIM pin to ground. This should keep the pin at a low enough voltage to stop the LED's from turning on while allowing the micro controller to function properly.

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