ISO7761: Creepage on Dig. Isolators

Florian Kolb

Part Number: ISO7761

Hi everyone,
i found the description of the creepage definition:
The shortest path between two conductive parts measured along the surface of the insulation.

A common practice is to add grooves in the PCB to increase the creepage distance. Is this correct, because the IC is directly above the PCB and no distance between the bottom side of the IC and (!) the PCB itself. I have the fear, that during certification the lab can complaint in the way that the bottom side of the IC "shorten" a possible creepage groove.

Does anyone got feedback during certification during usage of grooves?

Best regards

1 month ago

0 Sara Milliken 1 month ago

TI__Prodigy 210 points

Hi Florian,

You are correct that adding a groove to the PCB increases the creepage distance. This is a common practice throughout the industry. You can take a look at our app note Digital Isolator Design Guide (Rev. G) (section 4.3) which discusses this process in more detail. Further, we have another FAQ ([FAQ] What is Comparative Tracking Index (CTI)? - Isolation forum - Isolation - TI E2E support forums) that is helpful when designing with PCBs that have different CTIs.

Let me know if you have any other questions or concerns.

Best,

Sara