ArduinoPinCurrent

ARDUINO PIN CURRENT LIMITATIONS:

Be Nice to your Arduino!

(Thanks to @CrossRoads !)

If you want the real details on these chips, CLICK to download their data sheets below:

Official DataSheet for ATmega328P (UNO, RoboRED etc.) : Media:Atmel-42735-8-bit-AVR-Microcontroller-ATmega328-328P Datasheet.pdf

Official DataSheet for ATmega1280/2560 (MEGA etc.) : Media:Atmel-2549-8-bit-AVR-Microcontroller-ATmega640-1280-1281-2560-2561 datasheet.pdf

A Few Definitions:
VOH - Voltage Output High (I/O Pin "HIGH")
VOL - Voltage Output Low (I/O Pin " LOW")
IOH - Current Output High (I/O Pin "HIGH")
IOL - Current Output Low (I/O Pin " LOW")

Detailed Vin, Voltage Regulator Power Considerations HERE

ATMEL ATMEGA328 (UNO and Duemilanove and YourDuino RoboRED) Current Specifications:

Absolute Maximum Ratings
DC Current per I/O Pin ............................................... 40.0 mA (Good Design Value is 20.0 mA)
DC Current VCC and GND Pins................................ 200.0 mA

1 VCC pin: Means these Arduinos can Source a total of 200mA
2 GND pins: Means these Arduinos can Sink a total of 400mA

Only the 32 pin surface mount packages (UNO Surface-Mount version) have 2 VCC pins.

Pin SOURCE Current Limitations:

NOTE: Although each I/O port can source more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed.

• The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not exceed 150 mA.
• The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 150 mA.
• If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition.

Pin SINK Current Limitations:

NOTE: Although each I/O port can sink more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:

• The sum of all IOL, for ports C0 - C5, ADC7, ADC6 should not exceed 100 mA.
• The sum of all IOL, for ports B0 - B5, D5 - D7, XTAL1, XTAL2 should not exceed 100 mA.
• The sum of all IOL, for ports D0 - D4, RESET should not exceed 100 mA.
• If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition.

<Arduino (UNO and YourDuino RoboRED) Chip Pin#s VS Ports:

ATMEL ATMEGA 640/1280/2560 (MEGA) Current Specifications:

Absolute Maximum ratings:
DC Current per I/O Pin ............................................... 40.0 mA
DC Current VCC and GND Pins................................ 200.0 mA

This apparently is saying you get 800mA to play with as there are 4 Vcc and 4 Gnd pins, further limited by subgroups of pins for Sink (IOL) and Source (IOH) current:

Pin SINK Current Limitations:

• The sum of all IOL, for ports J0-J7, A0-A7, G2 should not exceed 200 mA.
• The sum of all IOL, for ports C0-C7, G0-G1, D0-D7, L0-L7 should not exceed 200 mA.
• The sum of all IOL, for ports G3-G4, B0-B7, H0-B7 should not exceed 200 mA.
• The sum of all IOL, for ports E0-E7, G5 should not exceed 100 mA.
• The sum of all IOL, for ports F0-F7, K0-K7 should not exceed 100 mA.

[looks like 800mA Total!]

NOTE: If IOL exceeds the test condition [(20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient)], VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition.

<Pin SOURCE Current Limitations:

• The sum of all IOH, for ports J0-J7, G2, A0-A7 should not exceed 200 mA.
• The sum of all IOH, for ports C0-C7, G0-G1, D0-D7, L0-L7 should not exceed 200 mA.
• The sum of all IOH, for ports G3-G4, B0-B7, H0-H7 should not exceed 200 mA.
• The sum of all IOH, for ports E0-E7, G5 should not exceed 100 mA.
• The sum of all IOH, for ports F0-F7, K0-K7 should not exceed 100 mA.

[looks like 800mA Total!]

NOTE: If IOH exceeds the test condition [(20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient)], VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition.