Guest georgedb Posted February 15, 2015 Report Share Posted February 15, 2015 I came accross the development board project to have a Maxim MAX6953 control up to 4 dot matrix 5x7 displays. I had a look at the PCB and schematic, but aren't current limiting resistors needed? The dot matrix displays are just row and column organised LED's I'd say and as far as I know, no resistor is integrated. A current limiting resistor could be integrated in the MAX6953, but I couldn't really find that in the datasheet (which is a bit too technical for me). I read something about the intensity that can be controlled, maybe through PWM, but even then I'd expect current limiting resistors... I'd be happy if they're no needed as it saves quite some hassle ;-) Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 15, 2015 Report Share Posted February 15, 2015 The resistor value from the ISET pin to ground sets the LED peak current. You can also program the IC to change (maybe using PWM) the (average) current in each digit. Quote Link to comment Share on other sites More sharing options...
Guest georgedb Posted February 15, 2015 Report Share Posted February 15, 2015 Thanks! OK, this works totally diffetrent then I expected, as I always learned the the LED will take as much current as it can (and therefore destroy itself), but this ISET limits the max current on the output pins in some sort of "soft" controlled setting... Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 16, 2015 Report Share Posted February 16, 2015 Many ICs regulate LED current without using series resistors. Examples are the LM3914, LM3915 and LM3916. Quote Link to comment Share on other sites More sharing options...
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