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When to Use Digital Isolators vs. Optocouplers

Authored on: Sep 8, 2009

Technical Paper

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Designing isolation into your system is critical to protect both systems and users from potentially hazardous voltages. Since industrial equipment must operate safely and reliably in the harshest environments—where strong electromagnetic fields, surges, fast transients, and high noise floors are the norm—designing reliable isolation circuits that deliver error-free operation over long equipment lifetimes can be challenging. This white paper discusses isolation circuits designed to withstand the rigors of industrial environments, comparing optocouplers to RF-based digital isolators to help you select the best technology for your application.

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Bob Lacovara Posted Jul 22, 2010

This is a nicely written comparison between opto-isolators and rf-isolators. If you work with optocouplers, then this is a recommended read if you aren't familiar with the RF alternative. For many applications, there seem to be advantages to the RF route. The article reminds me of a long-past design that I executed on an RS-232 AB switch. The primary requirement was that there be no copper/copper interconnection between A, B and C ports. (Yep... it ran on three distinct power supplies.) The optos available then gave me some tussel, but the design made it out the door eventually. Dealing with the analog circuitry and voltage translation for "legal" RS-232 was part of the headache. In another application, I used a pair of couplers in the feedforward and feedback path of an analog signal conditioning circuit that needed very high isolation between the process and the measurement electronics. This was a design where the analog optocoupler worked very well... the RF isolator wouldn't have fit quite as nicely. For many more conventional applications, though, and partiuclarly in speed and power consumption, the ISOpro RF isolator is worth a look.

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hm Posted Aug 14, 2010

This is nice isolator tutorial useful for both novice and experienced. Do we get these new isolators in MIL QPL approved product range? Are they available for -55 C and work at 55,000 feet or higher? What is their reliability data and have they been used in aerospace applications? Also, is it possible to get dual direction isolators? They are needed for many communication and bus architecture. Also, I may like to see 0.05% linear isolator made with this new RF isolation technique.

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GREATTerry Posted Aug 16, 2010

There are several vendors actively provides the RF isolation interface. It will be good to see how the market evolve. It is time to think about this better approach. Linear Technology do similar product with her great power supply family together so it also care the power across the isolation barrier that may make the application more sexy.

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komodo2k9 Posted Jul 29, 2012

pretty sad to go to all the effort of signing up inorder to take a look at a paper; just to find out that either the link is broken or this is just another site looking to generate leads for some marketing firm

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FredDagg Posted Aug 10, 2012

Same here - this is hopeless

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