Another Driving LED question

[ryamac]

Hi.

Im wanting to drive LED's using a MAX6974. My problem is that the driver can only output 5 to 7 volts and the LED's run off 12V. Why 12V, well there are 3 RGB LED's per pixel. And these LED's come on a strip with there own resistors cuttable every 3 LED's. As this is is going to be a square RGB matrix there are going to be a lot of LED'S, 300 RGB SMB which makes 100 pixels.

My question is... what would you do to 'step up' the voltage. Ive already looked in quad CMOS inverters and optocouplers. The optocouplers look to be the best option so far, but only being quads there are going to be a lot of them. Anything else you guys can think of?

 

[Laplace]

The LED driver outputs of the MAX6974 have a current sinking interface. They do not "output 5 to 7 volts" as stated. Each MAX6974 will drive at most 16 pixels with multiplexing enabled, so how will you drive 100 pixels "using a MAX6974"? Also, the MAX6974 is intended to drive each LED individually so why would you use an LED configuration driven in tandem requiring 12 volts?

 

[ryamac]

Hi Laplace.

Im aware that this chip has a current sinking interface but the data sheet also states that the anode voltage should range from 3V to 7V. I would really like to make a pixel that has 3 smb RGB Leds. The pixels will be spread 16 per meter, so i need the light intensity and the strip is cuttable every 3 LEDS.

At the moment i will only use one chip to test a proof of concept, but these chips can be cascaded so this is how i plan to expand the project. Once i have eight pixels working i will expand.

If you can think of a better chip that would do this job better, or really recommend that i only use one RGB LED per pixel , i open for suggestions.