Finding a suitable Mosfet

[JErik.1]

I am working on reparing a battery charger for a campervan and searching for a replacement for Mosfet partnumber h7na80fi.

Is there any suitable one?

[Andrew Neil]

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@JErik.1 wrote:

replacement for Mosfet partnumber h7na80fi.

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Put that part number into your favourite internet search engine - you should be able to find a datasheet.

Use the parameters from that datasheet as the basis for your search for a replacement.

https://www.st.com/en/power-transistors/power-mosfets.html

 

[JErik.1]

Thanks for your reply.
I have already done as you suggested and thought I found a suitable replacement (stw9nk90z) but was unsure if I missed something important in the data comparison.
among other things, there is quite a difference in Rise Time (tr) and Total Gate Charge (Qg) between this two, and I'm unsure if that can make it not to work..
That's why I'm asking here where the pros are.

[Peter BENSCH]

h7na80fi stands for the long discontinued STH7NA80FI. It was an n-channel MOSFET in the package ISOWATT218. Unfortunately, this package has also been discontinued for a long time, so that you can no longer find a direct replacement at ST.

If you can't find the STH7NA80FI at any dealer (you always have to be careful on Ebay and the like), then you could use an alternative in the TO-247 and insulate it from the heat sink with e.g. an mica insulating layer.

The parameters to be selected depend on your device, a similar device could be the STW6N90K5 with similar switching times, but much lower gate charge (typ 11nC vs 58nC). Although the single pulse avalanche energy is higher for the STH7NA80FI, the Rdson of the STW6N90K5 is ~45% smaller, which means that less energy is dissipated.

The only disadvantage of the newer STW6N90K5: the gate threshold voltage is higher. While the STH7NA80FI can already drive 6A current at 5V gate voltage, the STW6N90K5 wants to see 8V at the gate for the same current. You would therefore have to check the voltage with which the MOSFET is driven.

Hope that helps?

Regards
/Peter

[JErik.1]

Thank you so much, exactly the kind of answer I was looking for.