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Where do we start? Optocoupler or Digital Isolator?

-October 09, 2012

So you need isolation in your design?  Unless I completely misunderstand the engineering mind, no one gets up in the morning thinking "Yes, I'm excited for the day!  I get to decide what to use to isolate my design today!!”  No, you add isolation to your design because you have to, not because you want to.  Designers incorporate isolation because of safety regulations or to reduce ground loops, etc.  That's it, nothing magical about it.

Now if you are under the same constraints of the rest of the world, your boss has told you that you need to add isolation in a small space, with lower power consumption, better performance and higher reliability. Oh, by the way, it needs to meet safety requirements and, of course, be low cost.  And this is where we start. How do you balance the competing requirements for protection against bursts and surges, design complexity, and cost, all while getting to market as quickly as possible to remain competitive?

As my parents always told me, you have choices with everything in life.  To incorporate isolation in your design you have choices too.  You can use optocouplers.  Why not?  They've been around forever.  It works.  All you need to do is use what's been used before. Simple!  You could also consider digital isolators but can you really achieve everything that you need to?  They've only been around for about 10 years?  Is anyone really using them?

So here's your dilemma. Do you go with what you've always used or do you try something that may make you a hero to the boss by solving his requirements.  Where do you want to start?  Here’s some good reading until next time!

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