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How to use resettable fuses?

colhany , 06-05-2022, 11:08 AM
Hello everyone
i wanted to know how to use resettable fuses in a PCB?
Do I just connect them in series with the supply or are there additional components needed?
And is a fuse enough for short circuit protection, or is it better to use something like an E-Fuse ic?
Thank you
qdrives , 06-06-2022, 09:35 AM
All depends. A PTC is slow, has a maximum voltage and a (high) resistance.
I have used a resettable fuse more for long term overload and not so much short circuit protection (going external).
E-fuse are components that can fail too.
Most fail safe are the non-resettable fuses.
colhany , 06-06-2022, 09:46 AM
So non resettable fuses are fast enough to protect against shorts?
qdrives , 06-07-2022, 01:51 PM
So it is the speed?
That also depends on the load profile. If you have soft-start or not.
The fastest is electronic. Both resettable and non resettable fuse are driven by temperature. So it needs to heat up first.
The (glass) fuses are - simply speaking - in fast and time lag variants. The fast can open in 10ms.

colhany , 06-07-2022, 01:54 PM
Thank you very much
robertferanec , 06-13-2022, 07:22 AM
Often, the regulators itself have a protection for shorts - means if there is a short, the voltage will not even come up (or only for a very short period of time). We often use fuses for overload protection (e.g. something drives higher currents than it should - but it is not necessary a short circuit).
colhany , 06-13-2022, 03:56 PM
Thank you very much, Mr Robert
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