Total Phase - Differences between I2C and SMBus

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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

V_HIGH

Fixed Voltage	3.0 to V_{DD_max} + 0.5V
V_DD Relative	0.7 to V_{DD_max} + 0.5V

2.1V -> V_DD

V_LOW

Fixed Voltage	-0.5 to 1.5
V_DD Relative	-0.5 to 0.3V_DD

to 0.8V

Max Current

3 mA

350 µA

For more detailed information, check out:

Related Products

Name	Description
Beagle I2C/SPI/MDIO Protocol Analyzer Part Number: TP320121	The versatile Beagle I2C/SPI/MDIO Protocol Analyzer is the ideal tool for the embedded engineer who is developing an I2C, SPI, or MDIO based product. The Beagle analyzer provides a high performance monitoring solution in a small and portable package.
Aardvark I2C/SPI Host Adapter Part Number: TP240141	Connect your Windows, Linux, or Mac OS X PC to I2C and SPI bus through USB with the Aardvark I2C/SPI Host Adapter. Multi-master, slave, and GPIO are featured in this versatile development and testing tool.
I2C Development Kit Part Number: TP120111	The I2C Development Kit is a comprehensive and cost-effective kit that bundles together a complete set of Total Phase's industry-leading I2C development tools and popular accessories.
Programming Kit Part Number: TP120311	The Programming Kit bundles together a complete set of tools for programming I2C- and SPI-based serial EEPROMs and Serial Flash chips both in-system and stand-alone.