I've been trying to figure out the PTC fuse I want to use in a little automotive power supply circuit and I'm a little disconcerted by the max Vdc ratings most of these things have.
For instance, looking at Littelfuse's offerings for SMD PTCs… I want something that trips at 3.5A. For the given trip current, only their higher package sizes (like 5mm x 4mm and up) have Vdc max ratings that are over 12V. Yet, they have stuff in the 1210 package that is listed as handling hold currents in the range I want.. albeit with a low max Vdc rating.
At a very basic level.. if the fuse is rated for a given current, why is voltage an issue? This is what I don't understand. 🙁