I have my 9 RGB LED circuit. A PIC 16F1825 running at 32MHz with 9 pins used to connect to a pair of ULN2003ANs - 6 pins to one of them and 3 to the other (maybe I would balance them out more in future - 4 and 5 - if the answer to this question is "yes").
The ULN2003ANs are then used to connect my RGB LEDs to 12v.
I have run my circuit for hours at a time and everything appears fine. The LEDs switch colours, flash and fade. I'm really just asking this question for my own due diligence and safety.
I've noticed that the ULN2003AN with 6 connections does get warm. I'm not sure how warm, but much warmer than room temperature but not warm enough to hurt / burn when I touch it.
My other ICs (MAX667 and PIC) do not get warm at all. The other ULN2003AN (with 3 connections) gets warm, but not as warm as the first ULN2003AN.
The ULN2003AN is, apparently, rated to 70 degrees Centigrade and I don't think it's anywhere near that (I really should buy something to measure this) but I'm curious as to whether I should bite the bullet now and pro-actively consider some kind of heatsink in the small space that I have available to me, or whether I'm concerned about nothing?
Any thoughts appreciated... firstly, I guess... is it normal with what the IC is doing? I guess that nearly all its transistors are changing state all the time with what is going on in the circuit. That must be expected to generate heat.
If I decided I wanted / needed a heatsink, would I just glue some metal to the top of the IC?