I3C Interface: Advantages and Disadvantages

This page explores the pros and cons of the I3C interface protocol, outlining its benefits and drawbacks.

What is the I3C Interface Bus?

The I3C (Improved Inter-Integrated Circuit) specification, version 1.0, was initially released in October 2018 by the MIPI Alliance, Inc. The specifications were updated in July 2021. I3C is a two-wire interface, similar to I2C. It offers a fast, low-cost, and low-power digital interface with more benefits compared to I2C, SPI, and UART. It is backward compatible with I2C and improves upon it. I3C uses less energy for data/control signal transport and uses fewer physical pins. The specification defines a multi-drop interface between host processors and peripheral devices, such as sensors.

Here are some key features of the I3C interface:

• Data Rate: Up to 33.3 Mbps (Max.) at 12.5 MHz using push-pull configuration
• I2C Compatibility: Coexists with legacy I2C devices on the same bus; supports legacy I2C messaging and static addressing
• Dynamic Addressing: Allows devices to be assigned addresses dynamically
• In-Band Interrupt: Uses the same communication bus for interrupts
• Multi-Master/Multi-Drop: Supports multiple masters and multiple devices on the same bus
• Hot Join Support: Allows devices to join the bus after it has already been configured
• In-Band Command Codes: Supports integrated commands within the communication stream

Benefits or Advantages of the I3C Interface Bus

Here’s a breakdown of the advantages of the I3C interface protocol:

• Backward Compatibility: I3C is backward compatible with I2C, allowing for seamless integration of I2C devices.
• Upgrade Potential: Offers a performance and power consumption upgrade to existing I2C and SPI interfaces.
• Dynamic Addressing: Eliminates the need for hardware-based address configuration, as devices get their specific address using dynamic address assignment. It also supports static addressing for I2C devices, behaving like the I2C standard.
• Simplified Interrupt Handling: The in-band interrupt feature eliminates the need for an extra interrupt pin.
• Reduced Pin Count: Requires only two signal lines, compared to the four lines needed by SPI.
• Collision Avoidance: The multi-drop capability and dynamic addressing technique help avoid collisions on the bus.
• Clear Master Handover: The standard clearly defines the master ownership and handover procedure.
• Integrated Commands: Supports in-band integrated commands, simplifying communication.
• Higher Data Rate: Offers a higher effective data rate (~33.3 Mbps at 12.5 MHz) compared to I2C (~3 Mbps at 3.4 MHz).
• Hot Joining: I3C slaves can join the bus even after it has been configured.

Drawbacks or Disadvantages of the I3C Protocol

Here are the downsides of the I3C interface protocol:

• Lower Data Rate than SPI: Offers a lower effective data rate compared to SPI (~ approx. 60 Mbps at 60 MHz).
• Limited Addressing: Supports only 7 bits for device addressing.
• New Standard: As a relatively new standard, widespread adoption across new devices will take time.