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Differences and connections between SMBus, I2C and PMBus protocols

Overview

SMBus（System Management Bus）、I2C（Inter-Integrated Circuit) and PMBus (PowerManagement Bus) are serial communication protocols and are widely used in data transmission between electronic devices. Although they are similar in some ways, there are some differences in functionality, application scenarios, and specifications.

I2C Protocol

I2CIt is a two-way two-wire synchronous serial bus protocol developed by Philips (now NXP). It is mainly used to connect microcontrollers and their peripheral devices, and supports multiple masters and multiple slaves. I2C uses two lines for communication:

  • SCL（Serial Clock）: Clock line
  • SDA（Serial Data）: Data line

The I2C supports different transmission rates, including standard mode (100 kbps), fast mode (400 kbps), and high-speed mode (3.4 Mbps).

SMBus protocol

SMBusIt is a subset of the I2C protocol developed by Intel and is mainly used for system management. SMBus adds some specific command and timing requirements on the basis of I2C to meet the needs of system management. SMBus usually has a transfer rate of 100 kbps, but it can also support higher rates.

Features of SMBus include:

  • Supports host and slave roles
  • Define specific commands and protocols
  • Added timeout and error detection mechanisms
PMBus protocol

PMBusis a communication protocol based on SMBus, specially used for power management and monitoring. PMBus defines a standard set of commands for controlling and monitoring power supplies such as power converters,Battery Management Systemand power module.

Features of PMBus include:

  • Based on the SMBus protocol
  • Defines standard command sets and data formats
  • Supports configuration, monitoring and troubleshooting of power equipment
Differences and connections

  1. Basic Agreement：

    • I2C is a basic serial communication protocol.
    • SMBus is a subset of I2C that adds specific features of system management.
    • PMBus is a SMBus-based protocol designed for power management and monitoring.

  2. Transmission rate：

    • The I2C supports a variety of transfer rates, including 100 kbps, 400 kbps, and 3.4 Mbps.
    • SMBus usually uses a transfer rate of 100 kbps, but can also support higher rates.
    • PMBus uses the transfer rate of SMBus.

  3. Application scenarios：

    • I2C is widely used in communication between various electronic devices.
    • SMBus is mainly used for system management and monitoring.
    • PMBus is designed for power management and monitoring.

  4. Command sets and protocols：

    • I2C provides basic communication functions.
    • SMBus adds specific commands and protocols for system management.
    • PMBus defines a standard set of commands for power management and monitoring.
Summarize

Although SMBus, I2C, and PMBus are similar in some ways, they differ in application scenarios, functions, and specifications. I2C is a basicSerial Communication Protocol, SMBus adds specific functions of system management on its basis, while PMBus is a SMBus-based protocol dedicated to power management and monitoring. Understanding the differences and connections of these protocols can help select the appropriate communication protocol in practical applications.