Terminology » What is I2C and I3C: Difference Between I2C and I3C

What is I2C and I3C: Difference Between I2C and I3C

I2C (Inter Integrated Circuit) and I3C (Improved Inter Integrated Circuit) are widely used serial communication protocols for connecting sensors, processors and peripheral devices in embedded systems. I2C is 2-wire (SDA, SCL) synchronous serial interface while I3C is also 2-wire with improvement over I2C and SPI protocols.

What is I2C?

I2C, or Inter-Integrated Circuit, was created by Philips Semiconductor (now NXP Semiconductors) in 1982. It’s a 2-wire (SDA, SCL) synchronous serial interface commonly used for short-distance communication between peripherals, processors, and microcontrollers.

Over time, many companies like Texas Instruments, Nordic Semiconductor, STMicroelectronics, NEC, Siemens, and Intersil have adopted and developed products compatible with I2C specifications.

I2C Interface Protocol

Initially, I2C was limited to 100 Kbps. However, the I2C bus now supports various speed categories, as shown below:

Modes	Data rate	Bus Direction
Standard mode (Sm)	Up to 100 Kbps	Bidirectional
Fast mode (Fm)	Up to 400 Kbps	Bidirectional
Fast mode plus (Fm+)	Up to 1 Mbps	Bidirectional
High speed mode (Hs mode)	Up to 3.4 Mbps	Bidirectional
Ultra Fast mode (UFm)	Up to 5 Mbps	Unidirectional

Key Features of I2C

Includes electrical and timing specifications and associated bus protocol
Two-wire interface using SDA (Serial Data) and SCL (Serial Clock) lines
Unique start and stop conditions
7-bit slave device addressing (can be extended to 10 bits)
Bi-directional data transfer
Acknowledgement after each transferred byte
No fixed transfer length

What is I3C?

The I3C specification was initially released in 2018 and updated in 2021. I3C stands for Improved Inter Integrated Circuit. It is a 2-wire digital interface similar to I2C, but with improvements over both I2C and SPI interfaces. The MIPI Alliance Inc. manages the I3C specifications.

I3C provides a low-power, low-cost, and fast digital interface, supporting multi-master and multi-drop connections between host processors and peripheral devices like sensors.

I3C Interface Protocol

Key Features of I3C

2-wire serial interface (SDA and SCL) with up to 12.5 MHz using push-pull configuration
Legacy support for I2C devices on the same bus
Dynamic addressing for I3C devices
Supports static I2C addressing, I2C messaging, and I2C Single Data Rate (SDR) messaging
Supports optional High Data Rate (HDR) messaging modes
Supports multi-drop and multi-controller capabilities
Supports In-Band Interrupt
Supports Hot-Join

Difference between I2C and I3C

The following table provides difference between I2C and I3C as per various parameters.

Parameters	I2C Interface	I3C Interface
In-Band Interrupt	Not supported	Supported
Effective Data Rate	Lower (Max. 3 Mbps)	Higher (Max. 33.3 Mbps)
Dynamic Addressing	Not supported	Supported
Energy Consumption	Higher	Lower
Hot Joining	Not supported	Supported
Advantages and disadvantages	I2C interface	I3C interface

Summary

I2C and I3C are serial communication protocols used to connect multiple devices in embedded and electronic systems. I2C has been a reliable industry standard for decades, offering simple and cost effective communication. I3C, developed as its successor, delivers higher data transfer speeds, lower power consumption, improved bus efficiency and advanced device management features while maintaining backward compatibility with many I2C devices.