Beyond the specs of the ISO721 digital isolator

Beyond the specs of the ISO721 digital isolator

Texas Instruments won a 2006 Product of the Year Award for its ISO721 digital isolator. I recently spoke with Ashish Gokhale, business development manager, about the need, challenges, and unexpected hurdles encountered while designing the part.

The Need

“In the past, optocouplers were sufficient for most industrial customers’ isolation requirements. However, our customers urged us to attain higher levels of performance that are not possible with optical techniques. TI developed a way to integrate high-voltage capacitors on-chip in a proven manufacturing technology in order provide higher data rates, faster propagation delays, higher reliability, better noise immunity, improved signal integrity, longer lifetime, and lower power consumption.

“The design and process team decided to focus on the concept of capacitive isolation, which required extensive research and fundamental development of a new technology.

The design team

A special cross-functional team collaborated to bring the diverse set of expertise needed to get the product together—mixed-signal IC design, process technology development, and packaging development, along with testing and reliability studies to ensure quality and applications knowledge to fully utilize the potential of this new technology.”

Design challenges

“This is the first time in the semiconductor industry that integrated capacitive technology for isolating up to 4,000 V has been developed and used successfully. The team had to work through many technical challenges to ensure that the product would withstand the high-stress environment that the product would be subjected to in its field of use without compromising the quality of performance.

“During the design process, we unexpectedly realized that it would be beneficial to both the end users and ourselves to initiate a process of revolution rather than evolution so we could offer something of real value. We saw an opportunity to provide the end user with an entirely new technology that would solve challenging system design issues and significantly enhance performance, rather than simply modify an existing product into something slightly better.”

Christina Nickolas