Maximum current of a microcontroller circuit

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I've recently purchased a few Teensy boards (Teensy USB Development Board), and I'm curiofgjmbus if there are limits built into microcontrollers for the maximum total current going through it. I know there is a maximum limit on how much current each pin can output (~25mA-40mA depending on the chip), but what about all pins at the same time?

Basically, I'm looking to drive 39 individual LEDs directly from the Teensy++ board without multiplexing, and I'm wondering if I can do so or if I need to get some Darlington arrays.

I know that Arduinos have a voltage regulator on-board that limits total current to about 250mA, but the Teensy board expects a power source that is already regulated. My hope is that if I plug in a 5V @ 1A power supply to the Teensy, I can utilize all of that power to drive the LEDs via the microcontroller at once. What do you think?

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The best place to find answers to voltage / current / power questions is the datasheet...
http://www.pjrc.com/teensy/datasheets.html

Search for "Electrical Characteristics"

h4t:
I know there is a maximum limit on how much current each pin can output (~25mA-40mA depending on the chip),

Nope...

30.1 Absolute Maximum Ratings*

DC Current per I/O Pin ............................................... 40.0 mA

*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.

The AVR processors used for Arduinos consistently have an absolutely maximum per pin current of 40 mA. Try to stay close to half that; 20 mA.

but what about all pins at the same time?

For the entire processor...

DC Current VCC and GND Pins................................ 200.0 mA

Basically, I'm looking to drive 39 individual LEDs directly from the Teensy++ board without multiplexing,

No problem. 200 mA - 30 mA for the CPU = 170 mA for your LEDs. 170 mA / 39 LEDs = 4.35 mA per LED.

Be sure to check the datasheet for "per port" limits.

and I'm wondering if I can do so or if I need to get some Darlington arrays.

If you plan to drive the LEDs at more than 4.35 mA then the answer is "yes".

My hope is that if I plug in a 5V @ 1A power supply to the Teensy, I can utilize all of that power to drive the LEDs via the microcontroller at once. What do you think?

In the words of the great Mr. Lizard, "We're gonna need another Timmy Teensy!" I think you would quickly turn your Teensy into slag.

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I know there is a maximum limit on how much current each pin can output (~25mA-40mA depending on the chip), but what about all pins at the same time?

Look in the "Electrical Characteristics" section of the data sheet for your particular device (you didn't specify which one you are using). Then go to the "DC Characteristics" subsection and below the chart there are some notes. Note 3 has the information you are seeking. I'm pretty sure you will need some driver transistors/ICs.

EDIT: CB types faster than I do.

Don

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Ah, I had been looking over the datasheet for things I understood, and didn't know thats what that meant. Thanks!

Each LED will require either 20mA or 35mA (depending on color), which raises another question: would Darlington pairs be overkill? I have a bag full of 2n2222s, whose datasheet says they can switch up to 1A (collector current max). If I used one 2n2222 transistor per LED, would that cause any problems?

My understanding is that Darlington pairs would be required for more significant current loads, but single LEDs don't need that amount of power. Am I correct on that at least?

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If I used one 2n2222 transistor per LED, would that cause any problems?

That should work just fine.

Lefty

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If I used one 2n2222 transistor per LED, would that cause any problems?

No problem that is how to do it.

Darlington pairs would be required for more significant current loads

Not strictly true. Basically Darlingtons have more gain than a single transistor so you need less current to drive them. There is also the popular ULN2003 array of Darlingtons, they are only half an amp but you get 7 (or 8) in one package.