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.

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

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Related Products

Name Description
Beagle I2C/SPI Protocol Analyzer
Part Number: TP320121

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

Aardvark I2C/SPI Host Adapter
Part Number: TP240141

USB interface to I2C and SPI for your Windows, Linux, or Mac OS X computer.
I2C Development Kit
Part Number: TP120112

A comprehensive kit that bundles a set of Total Phase's industry-leading I2C tools and accessories.
EEPROM Programming Kit
Part Number: TP120510

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