I've been reading the various threads on power dissipation limits on the TLC5940 and am just more confused than ever.
I'm hoping to use 32 30cm strips of single colour LEDs @120ma each on 12v over 2x 5940. They have their own resistors built in to take a 12v supply and run straight off my bench supply fine. I've used a single 5cm strip at 20ma and the TLC dims it nicely.
I would assume then that Vout should be 0 or as close as? With practically no power dissipation needed from the 5940, is this correct?
Hi DC42, thanks for your response
So from that I get an additional drop of 1v at 120mA, giving me 11v at the LEDs? I might be able to live with that. Does that have any effect on power dissipation? To my mind if the LEDs are drawing 1v less than they should the power dissipation of the package would be 0?
Demonic69:
Hi DC42, thanks for your response
So from that I get an additional drop of 1v at 120mA, giving me 11v at the LEDs? I might be able to live with that. Does that have any effect on power dissipation? To my mind if the LEDs are drawing 1v less than they should the power dissipation of the package would be 0?
No, the 1v appears between each output and ground, so the package dissipation is 1v * 120mA per output. You need to add the power dissipated by the its internal workings, which is 5v * 60mA maximum.
dc42:
No, the 1v appears between each output and ground, so the package dissipation is 1v * 120mA per output. You need to add the power dissipated by the its internal workings, which is 5v * 60mA maximum.
That helps a bit, the only numbers I'm confused about now are DCn, I'm not using dot correction, and dPWM, I don't know the duty cycle, would I calculate that at 4096 to be safe?