EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: danners430 on January 29, 2019, 01:39:58 pm
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Afternoon folks,
I've got a project ongoing at the moment, involving umpteen tiles being installed in a control panel. These tiles are all different and mostly unique, but the various LED configurations can be generalised into 6 "master" designs, with only the necessary LEDs for the individual tile being added at installation. Saves me money on PCBs :D
However, I've come across a minor problem - what do I do with unused pins on the driver chips, the WS2811? I'm guessing it won't do any harm leaving them NC, but would best practice be to tie them to ground, since the chip is open drain...?
Any clarification would be much appreciated!!
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Where did you get the idea the WS2811 LED outputs are open drain? If one carefully reads its datasheet (https://cdn-shop.adafruit.com/datasheets/WS2811.pdf), it tells you that they are PWMed 18.5mA (typ.) current sinks, that drop 0.4V (presumably minimum). Why would you think grounding them would be desirable? Depending on how the current sinks are implemented, that could disrupt non-grounded outputs.
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That was my assumption... hence my question - assumptions make fools!!
I'm guessing then it would be more desirable to either leave them NC, or fit "dummy LEDs" in the form of resistors (3V @ 18.5mA ~ 160Ω)...?