Summary:
You must distinguish between "guaranteed operating conditions" and "absolute maximum ratings". Also between current from an eg a logic high output pin at a usefully high voltage and short circuit current from a pin.
At 80 mA you are exposing the IC to conditions that exceeds the manufacturer's guarantees for product survival and the manufacturer explicitly advises that such practices may cause permanent damage to the IC.
YMMV :-)
Operating and Absolute-maximum figures
Manufacturers publish data that tells you what conditions they guarantee a device will meet in practice when operating normally. They also publish absolute maximum ratings for a device, beyond which damage to the device may occur.
On pages 519 and 520 are tables that specify the voltage and current output conditions which Atmel guarantees. Not that as current increases the voltage drops due to increased voltage drop across the internal circuitry. They do not specify what current you can get when you load a high output pin down to almost 0 Volts - but you can be sure it would be more than the maximum guaranteed figure and that it would probably risk damaging the IC.
The most important specification with respect to your question is on page 317 of the ATmega328 datasheet
This says
29.1 Absolute Maximum Ratings*
DC Current per I/O Pin ................................................ 40.0mA
and
- NOTICE Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent damage
to the device. This is a stress rating only and
functional operation of the device at these or
other conditions beyond those indicated in the
operational sections of this specification is not
implied. Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.
"Absolute Maximum Ratings" are in all reputable data sheets and mean just what they say. They are the absolute maximum at which the device is guaranteed by the manufacturer not to suffer permanent damage at. Usually the guaranteed operating conditions are lower than the absolute maximum ratings.
You say that "you have tried this on every pin. Note the manufacturer's comment
- Exposure to absolute maximum rating
conditions for extended periods may affect
device reliability.
Here "extended periods" is at the manufacturer's and Murphy's discretion.
Chances are you have not damaged the IC. But if you operate it at above maximum values you may. And if you operate it at above maximum operating values you may get misoperation in practice. "Proper" designs must always observe operating limits set by the manufacturer.
According to the data sheet, the 3 RGB LEDs are electrically separate. This means that you can connect them in series, using a higher voltage with fewer resistors and transistors. Nick Alexeyev's answer then applies. Assuming a 36 volt power supply, and strings of 8 for green and blue, 16 for red, and 24 for IR, total is 18 channels. I would not go with Nick's suggestion of 48v/12x strings for green and blue, since there isn't enough excess voltage for the limiting resistors to operate reliably, particularly with the Vf variations given in the data sheet. I'd expect that you'd need to measure the voltage drop of each string and tailor the limit resistor values accordingly.
What I think you've missed is power. Assuming 20mA for each LED, total power is 3.6 watts each for green and blue, 2.3 watts for red, and 1.5 watts for IR. Total power is 11 watts in the LEDs. I have no idea how you're going to heatsink this. Well, I do, but it involves using a beryllium oxide substrate for your LED PC board, bonded either to a pretty hefty heat sink, or maybe a TEC cooler. You want the LEDs to run as cool as possible for better lifetime. But trying to do it with FR4 is asking for early death of your LEDs. Similarly, you would also need to calculate the dissipation in your limiting resistors, although for the values I've given I'd expect total dissipation in the 4-5 watt range, and this can be handled with forced air cooling. And with the cooling requirements indicating a certain amount of increased size, I don't think you really need to worry about minimizing the driver board size, although at 18 channels you shouldn't have much difficulty.
Best Answer
First, the TLC59116 should be able to drive 120mA Per channel, ideally with a small VLED - VF voltage of VOL, to minimize heat issues. The higher the "unused" voltage, the less current can be driven per channel before thermal shutdown happens.
A TI employee responded to a user with the TLC59116. More info at the link
Question:
Answer:
So you need to match your LED VCC to the Forward Voltage of each led on that channel. Don't have too much left over voltage, as the internal transistor will need to dissipate that into heat.
From the Datasheet:
As for more current, you can tie multiple channels together.