United States
 
Knowledge Base - Article 10040

Differences between I2C and SMBus

In general, the I2C bus and SMBus are compatible, but there are some subtle differences between the two that could cause some problems. The following table summarizes the differences between the two buses.

Clock Speed Comparison

I2C
 SMBus
Minimum none 10 kHz
Maximum 100 kHz (Standard mode)
400 kHz (Fast mode)
2 MHz (High Speed mode)		 100 kHz
Timeout none 35 ms


Electrical Characteristics Comparison

I2C
 SMBus
VHIGH Fixed Voltage: 3.0 to VDD_max + 0.5V
VDD Relative: 0.7 to VDD_max + 0.5V
 2.1V to VDD
VLOW Fixed Voltage: -0.5V to 1.5V
VDD Relative: -0.5 to 0.3VDD
 to 0.8V
Max Current 3 mA 350 µA

For more detailed information, check out:

Related Products

Product Name Description
Beagle I2C/SPI Protocol Analyzer Beagle I2C/SPI Protocol Analyzer

Non-intrusive bus monitor for embedded engineers working on I2C- or SPI-based products.

Aardvark I2C/SPI Host Adapter Aardvark I2C/SPI Host Adapter

USB interface to I2C and SPI for your Windows, Linux, or Mac OS X computer.
I2C Development Kit I2C Development Kit

A comprehensive kit that bundles a set of Total Phase's industry-leading I2C tools and accessories.
EEPROM Programming Kit EEPROM Programming Kit

A bundled set of tools for programming I2C- and SPI-based serial EEPROMs.