ARDUINO PIN CURRENT LIMITATIONS:

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Questions/Comments/Critique: terry@yourduino.com

More Detail: http://arduino-info.wikispaces.com/ArduinoPinCurrent

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")

ATMEL ATMEGA328 (UNO and Duemilanove) Current Specifications:

Absolute Maximum Ratings

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

Arduno (UNO and Duemilanove) Chip Pin#s VS Ports:

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.

ATMEL ATMEGA2560-1280-640(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.