Digital Isolators vs Optical isolators

Designers come across the need to have isolation in their circuits. Isolation basically helps to achieve electrical path without the need to have a physical connection. So, if a designer comes across a design to have isolation between input and output, then he might have to think of which type of technology to use. The need comes for a isolator when the circuit board designed has to operate in harsh environments. The basic problem in such harsh environments is the surges that can occur to damage your devices. One has to remember that isolation helps noise to get isolated, helps to isolate unintended problems which cause system failure. Basically, there is no direct current flow between the two sides of the isolator. 

Take ADUM152N as an example of Digital isolator from analog Devices.

Specifications those are important to isolator selection:

• Technology Type – Opto based, inductive, magnetic, capacitive
• Number of channels
• Data Rate allowed
• Isolation rating – the insulation rating of the isolator decides the cost
• Working/Supply voltage – Input and Output (Sometimes Input and output voltage can be different which helps in level translation)
• Internal protection
• Propagation delay
• Operating Temperature
• UL Recognition/VDE conformity certificate
• Common mode transient Immunity (CMTI)
• Reliability - FIT rate – Failure in Time (Fails/10^9 hours)

Application Areas:

·         Medical

·         Industrial

The below table explains the difference between digital isolator and optical isolator.