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By tiandao
#181731
Hi all, I plan to get some pcbs made up, very similar to the following:
http://kitili.en.made-in-china.com/prod ... turer.html

http://en.ofweek.com/manufacturer/3w-rgb-power-led

I have got hold of some 3w RGB LEDs - this type: http://www.rapidonline.com/electronic-c ... led-200101

I'm wondering what to connect the thermal pad on the bottom of the leds too, it appears to be connected to the VCC side of the red chip in the led. I will be running them in series so I can't connect the three heat pads to a common plane in the pcb.

I'd like some suggestions on how to do this, the PCB in the first link I posted is hard to examine what the heatsink pads are connected too, but they look like they are all on the same plane?

cheers
#181735
Usually the heatsink pad is connected to ground.

The image of the board has the LEDs running in series.. To me, the silkscreen is wrong though.. Search Google, there are thousands of schematics and board layouts for high wattage RGB LEDs.
By n1ist
#181741
I agree; the silkscreen is wrong. I would guess the board has a common anode and three separate cathodes; at least the traces look like they are connected that way.

As for the heat slugs; if they are not isolated, then they need to go to their own copper pours on the PCB
/mike