Mosfet NTMFS4899NF

[LA9CHA Thorvald]

Hello, anybody who know where to buy 8 pieses of the above mosfet?

[greg_simons]

Our old friends aliexpress have them, quality unknown...
Greg.

[Diabolical Artificer]

Doesn't look anything special apart from an intergrated schottky 30v 75A would another similar type not do the job?. Always amazes me when little parts like this are rated at such high current.

Andy.

[duncanlowe]

Originally Posted by Diabolical Artificer

Doesn't look anything special apart from an intergrated schottky 30v 75A would another similar type not do the job?. Always amazes me when little parts like this are rated at such high current.

Andy.

You have to be very careful about rated currents on MOSFETs. The real limitation on MOSFETS is the power dissipation and heat sinking. So a device rated at 30A for example means that 30A won't blow it up (usually a bond wire limitation). But if that current flows for long enough, and any heat generated in the siliconas a result of RDSon x I it's likely to be a fraction of that for any time. It also applies only when fully ON and not in the linear region where RDS is higher. So switching on and off a lot can also increase power dissipation.

This very badly caught a company out. Their Chief of Electronics was actually Chief of designing by data sheet and missed this important point and threatened to sue ST over misleading specs because they even ignored the prorotype testing stage before ordering a production size batch. When they did do some testing, the lids came off. The specs were fine, he was clueless that's all.

[Diabolical Artificer]

Aye, sounds about right Duncan, obviously any parts wattage rating is only as good as how much heat you can get rid of.

I've had a dig around and found some 75N03 fets - https://pdf1.alldatasheet.com/datash...EMI/75N03.html , pulls, but test good if you want them. I think I have about 7.

Andy.

[Radio Wrangler]

They are listed as obsolete.

It is possible that the same die is available in a different package.
It is possible that it went obsolete because it has been superseded by an improved part.

These mean that you need to look for a different part number having different specifications which meets or improves on those of the original part.

In order to progress, you need to understand the circuit the original device was used in, so that you can judge which specifications are important, and which give you some freedom. As it's a surface mount part, you will need something in the same package as a definite 'must have' requirement. Onsemi would be the logical place to start searching to see if they have a suggested replacement.

There is no easy answer which can be given without even knowing the application.

There may be some stocks somewhere in the world left at a distributor, but large authorised distributors are required by their accountants to minimise inventory of parts without mass turnover, so they dump them on the market.

This secondary market is where the chip fakers operate. You don't know whether you're dealing with someone who has real ones, or with a faker ready to write that part number on anything in what looks like the right package.

The safest route is to find a current part which will do the job, and which you can still get from an authorised distributor.

Additionally, this sort of MOSFET does not usually die quietly, there may be other damage around it.

A long answer because of a short wquestion.

David

[duncanlowe]

Originally Posted by Radio Wrangler

There is no easy answer which can be given without even knowing the application.

The safest route is to find a current part which will do the job, and which you can still get from an authorised distributor.

Additionally, this sort of MOSFET does not usually die quietly, there may be other damage around it.

David

Clipped some parts of your reply, but agree with all of it. Just wanted to add my comments to these particular points.

Without knowing the application it's not possible to know which parameters are important. The nature of the load, whether it's simply on / off or linear, etc etc.

Without knowing which parameters are important to match, especially if the device is being operated in the linear (not fully on or off) region.

All of the applications I have been involved with have been fairly straightforward loads being simply on off switches for low voltage non-inductive loads, or straightforward brushed DC motors. Sometimes they failed simply open circuit. But other times they failed low resistance D-S. I say low resistance but R of 1 or 2 ohms, which is much higher than the RDSon. So the die got hot. VERY hot. So there was other damage but it was simply by melting. On the other hand although not in my field of experience they are often used for inductive things like SMPSUs, and the intrinsic body diode is important, so nasty EMFs that would be clamped by this aren't when the FET fails. In this type of application, a failure does indeed wreak havoc. So again, it's important to know the application.

[Syrinx1]

You could try alltransistors.com to try and find a suitable equivalent.

[LA9CHA Thorvald]

Ok fine! Thanks to all answers§