Low power bidirectional I2C isolators extend industrial isolation lifetime

December 14, 2012 // By Paul Buckley
Texas Instruments Incorporated has introduced a bidirectional isolator family compatible with I2C interfaces that claims to consume as much as 38-percent lower power than competitive devices.

Each of the new integrated circuits (ICs) can replace a typical implementation of 16 or more discrete devices to isolate the I2C signal in industrial applications. In addition, the ISO1540 and ISO1541 offer better transient immunity and faster switching times than optocouplers. This performance provides longer-lasting isolation in a variety of applications, such as power supplies, networking, telecommunications, Power over Ethernet (PoE) and battery management systems.
The ISO1540 and ISO1541 employ a capacitive isolation technology with a silicon dioxide barrier (SiO2) to separate logic input and output buffers. This approach extends the lifetime of the isolators by more than three times compared to optocouplers or magnetic isolators. The ISO1540 provides two isolated bidirectional channels for clock and data lines for use in applications that have multiple masters. The ISO1541 includes a bidirectional data and a unidirectional clock channel for use in single-master applications. The I2C isolator family joins TI’s portfolio of long-lifetime digital isolation products, including devices with isolated CAN or RS-485 interface; isolated amplifiers; or other isolated functions for industrial applications.

The ISO1540 and ISO1541 deliver a maximum current of less than 8.5 mA at 5 V, the ISO1540 and ISO1541 reduce power consumption by up to 38 percent compared to competitive ICs, reducing heat generation in industrial applications.

The devices have a maximum propagation delay of 62 nanoseconds which claims to be 52-percent better than competitive ICs, enabling faster data transfer.

With a ± 50-kV/us typical transient immunity the devices provide better reliability in harsh environments.

Isolated bidirectional communications is accomplished within these devices by employing an offset configuration that prevents device latch-up and ensures reliable operation.

To provide secondary power supply to the ISO1540 and ISO1541, the SN6501 transformer driver can be used in conjunction with a transformer, rectifier and a regulator, such as TI’s 5 V TPS70950 or 3.3 V TPS70933. The result is a small, low-cost, high-efficiency, low electro-magnetic interference (EMI) solution for generating