A communication bus in a lithium battery system is a network that allows the battery management system (BMS) to communicate with individual battery cells and other components of the system. This network is used to monitor and control the charging and discharging of the batteries, as well as to ensure that each cell is operating within safe limits. The communication bus can be wired or wireless, and it typically uses a protocol such as CAN (Controller Area Network) or SMBus (System Management Bus) to transmit data between the components of the system. Today we are going to introduce two communication bus-SM Bus and I2C Bus. Let’s move on.

What is SM Bus?

The System Management Bus (SMBus) is a communication bus used for low-speed communications in a computer system. It is used for simple communication between different components on the motherboard, such as the CPU, memory, and peripheral devices. The SMBus is responsible for tasks such as monitoring system temperatures, controlling fans, and managing power consumption. It is a subset of the I2C (Inter-Integrated Circuit) bus and uses a two-wire interface for communication.

The Features of SMBus Include:

  1. Low-speed communication: SMBus is designed for low-speed communication, making it suitable for communicating with low-speed devices like temperature sensors, fan controllers, and power management chips.
  2. Simple protocol: The SMBus protocol is simple and easy to implement, making it a cost-effective solution for communication between devices.
  3. Standardized protocol: SMBus is a standardized protocol, meaning that devices from different manufacturers can communicate with each other using the same protocol.
  4. Built-in error detection: SMBus has built-in error detection and correction mechanisms to ensure data integrity.
  5. Power management: SMBus supports power management features, such as device sleep and wake-up, to help reduce power consumption in a system.
  6. Hot-plugging: SMBus supports hot-plugging, allowing devices to be added or removed from a system without the need for a system reboot.
  7. Low pin count: SMBus uses a low pin count, which helps reduce the complexity of a system and the cost of manufacturing.

Advantages of SM Bus:

  1. Easy to use: SM Bus is a simple and easy-to-use interface that enables communication between different components of a computer system.
  2. Low power consumption: SM Bus is designed to consume very little power, making it ideal for use in portable devices like laptops and tablets.
  3. Standardized interface: SM Bus is a standardized interface that is used across different computer systems, making it easy for manufacturers to design and produce compatible components.
  4. Cost-effective: SM Bus is a cost-effective solution for communication between different components of a computer system, as it does not require expensive hardware or software.

Disadvantages of SM Bus:

  1. Limited bandwidth: SM Bus has a limited bandwidth, which means it can only transfer a limited amount of data at a time. This can be a bottleneck for high-performance systems that require a lot of data transfer.
  2. Limited distance: SM Bus is designed for use within a single computer system and has a limited distance over which it can communicate. This makes it unsuitable for use in large-scale networks.
  3. Lack of versatility: SM Bus is designed for a specific set of tasks and is not as versatile as other communication protocols like USB or Ethernet.
  4. Limited compatibility: SM Bus is not compatible with all computer systems, which can limit its usefulness in certain situations.

What is I2C?

I2C (Inter-Integrated Circuit) is a communication protocol used for transferring data between integrated circuits or microcontrollers. It was developed by Philips Semiconductors (now NXP Semiconductors) in the 1980s and is now widely used in various electronic devices.

Features of I2C include:

  1. Two-wire communication: I2C uses only two wires, a serial data line (SDA) and a serial clock line (SCL), for communication between devices.
  2. Master-slave architecture: I2C uses a master-slave architecture, where the master device initiates the communication and controls the data transfer.
  3. Multiple devices on the bus: I2C allows multiple devices to be connected to the same bus, with each device having a unique address.
  4. Bit-oriented protocol: I2C is a bit-oriented protocol, where data is transferred one bit at a time.

Advantages of I2C include:

  1. Simplicity: I2C is a simple and easy-to-implement protocol, making it ideal for low-speed communication between devices.
  2. Low power consumption: I2C uses less power than other communication protocols, making it suitable for battery-powered devices.
  3. Flexibility: I2C allows multiple devices to be connected to the same bus, making it a flexible and cost-effective solution for communication between devices.
  4. Addressing: I2C uses a unique addressing scheme, which allows multiple devices to be connected to the same bus without the need for additional hardware.

Disadvantages of I2C include:

  1. Limited speed: I2C is a low-speed protocol, with a maximum data transfer rate of 400 kbps.
  2. Limited distance: I2C is designed for communication within a single circuit board or device, and is not suitable for long-distance communication.
  3. Limited number of devices: The number of devices that can be connected to an I2C bus is limited by the available addresses and the bus capacitance.
  4. Limited error detection: I2C does not provide robust error detection and correction mechanisms, making it vulnerable to data corruption and transmission errors.

Comparison Between SM Bus and I2C

Feature SM Bus I2C
Full Form System Management Bus Inter-Integrated Circuit
Developed By Intel Corporation Philips Semiconductors (Now NXP Semiconductors)
Purpose Used for communication between low-speed peripherals and the motherboard Used for communication between integrated circuits
Communication Speed Up to 100 Kbps Up to 3.4 Mbps
Maximum Devices Up to 255 Up to 128
Addressing Scheme 7-bit and 10-bit addressing 7-bit addressing
Voltage Range 2.0V to 3.6V 1.8V to 5V
Clock Speed Synchronous and asynchronous operation Synchronous operation only
Error Detection Uses CRC error checking Uses ACK/NACK error checking
Applications Used in desktops, laptops, and servers Used in embedded systems, sensors, and smart devices

SMBus (System Management Bus) and I2C (Inter-Integrated Circuit) are two communication protocols used for communication between different electronic components. Although these two protocols share some similarities, they differ in several aspects.


1. Voltage Levels: One of the main differences between SMBus and I2C is the voltage levels. SMBus operates at a lower voltage level (3.3V) than I2C (5V).

2. Speed: SMBus is slower than I2C. SMBus has a maximum speed of 100 kbps, while I2C can operate at speeds up to 3.4 Mbps.

3. Addressing: SMBus uses 7-bit addressing, while I2C can use both 7-bit and 10-bit addressing.

4. Hardware: SMBus has a more stringent hardware requirement than I2C. SMBus requires a dedicated controller, while I2C can use a simple microcontroller.


1. Master-Slave Architecture: Both SMBus and I2C follow the master-slave architecture, where one device acts as the master and controls the communication, and other devices act as slaves.

2. Serial Communication: Both SMBus and I2C use serial communication for data transfer, where the data is transmitted bit by bit.

3. Acknowledgment: Both SMBus and I2C use acknowledgment to confirm the successful transmission of data.

4. Bi-Directional Communication: Both SMBus and I2C support bi-directional communication, where data can be transmitted in both directions.

In summary, SMBus and I2C are two communication protocols used in different electronic components. Although they share some similarities, they differ in voltage levels, speed, addressing, and hardware requirements.