I2C switches aren't confused by addresses

A NXP Semiconductors product story

Edited by the Electronicstalk editorial team Jun 12, 2002

A novel family of I2C-controlled switches can connect multiple devices with the same I2C address on a single bus, removing the need for multiple I2C buses or bus switches.

Philips has developed the first family of I2C-controlled switches that can connect multiple devices with the same I2C address on a single bus - a task that previously required multiple I2C buses or bus switches.

By using Philips' PCA954x I2C switches, design engineers can greatly simplify board layouts for cost savings and additional flexibility.

This breakthrough product is significant because of the wide range of applications in the computing, communication, telecomms, networking, industrial and consumer markets that depend on sharing one I2C bus with multiple devices with the same I2C address.

"IBM needed to use over 20 identically addressed I2C slave devices on its new IBM E-Server X Series 255 design", said Fernando A Lopez, engineer, IBM Server Division.

"Using two of the new PCA9545 four-channel switches with interrupt and reset provided a very simple and cost effective solution.

This has allowed multiple I2C master devices to talk to one I2C slave device at a time.

Since the PCA9545 I2C switch can also perform voltage level translation we were able to communicate with I2C buses and devices operating on a wide range of voltage levels.

This feature saved us the logic needed to implement I2C bus voltage translation".

"IBM has found that Philips' PCA9545 is a far better solution for our needs than any other solution currently on the market.

It takes up less board real estate and provides increased functionality and I2C-bus signal integrity", added Andy Heinzmann, senior engineer, IBM Server Division.

"Philips is strengthening its leadership in I2C technology by enabling design flexibility and savings in board space and lower system costs", said Pierre-Yves Lesaicherre, general manager, Specialty Logic Product Line in the Semiconductors Division of Philips.

"As the only semiconductor manufacturer offering these devices, the PCA954x family gives our customers a key differentiator as they bring new designs to market".

Philips' PCA954x switches are designed for I2C buses or SMbuses where multiple devices have the same address and/or different voltage levels.

These switches allow voltage level shifting between devices operating at 5.0, 3.3, 2.5 or 1.8V at serial clock frequencies up to 400kHz.

They provide multiplexing and interrupt controlling to eliminate the need for glue logic and general purpose I/Os.

Four devices with two, four, or eight-channel configurations are currently in production.

In addition, these switches are equipped with a hardware reset pin that returns the device to the default state of no channels selected, thereby circumventing the usual step of cycling power to restore the bus from a lockup situation - a major concern in critical server applications.

(This was Electronicstalk's Top Story on 11 June 2002).