Electronics > Projects, Designs, and Technical Stuff
Cheap LED driver and cheap RGB LED quality
3dgeo:
Hm, I don't like that IS31FL3741 has 9 anodes, it's a bit too much on routing and it reduces light significantly. To get same light amount I have to drive each led @~23mA, that's not a big deal, but cheap LEDS may not like that. Also if I use only 8 anodes I would get only 104 leds instead of 105 I need :( And leaving out 3 cathodes and using all 9 anodes seems a bit wasteful ???
Big advantage IS31FL3741 is a memory buffer for entire matrix! In my current configuration I have to send new data if I change active fet.
Also there is "open detection" and "short detection" – I'm guessing it's used for key press detection? :o If so than's a very nice feature!
IS31FL3731 – can't see myself using this chip.
LP5036 – has very nice features, tho way too expensive.
I will nag LCSC about IS31FL3741, if they can get it at descent price I'll role with them, otherwise IS31FL3236A.
3 * IS31FL3236A I would give 35*3 + 1 extra output per chip (I'm using free outputs to reduce resistance on R_EXT and increase LED current if PSU allows it).
--- Quote from: mariush on November 17, 2019, 10:16:59 am ---but it would be a bitch to do the wire layout for a 35x3 display ... lots of traces on just two layers. Going with 4 layers would significantly reduce the PCB difficulty but what you save on led drivers, you put in the circuit board.
--- End quote ---
Tell me about it ;D I have working 2 layer PCB prototypes with 45x7 (3 ICs with 16 outputs), and it is tight..... Tho I managed to squeeze 0.3mm traces, but if my assumptions are correct with new ICs I have room for 0.15mm at best and some traces are 25cm long.
No, my assumptions were wrong, if I use this chip routing will be at the same level or even simpler!
Edit:
I noticed in datasheet that IS31FL3741 has resistors on every input (20/51ohms), but no info on them. If they are required this chip is not suited for me, I don't have place for 39 resistors on the PCB, plus PNP cost will be huge...
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