MOSFET help.

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07-21-2005, 10:04 PM
Nanometer

MOSFET help.

Before I begin, I would like to say I know I made a mistake and I wont ever do it again. First off my motherboard is a P4C800 Deluxe. I had copper heatsinks on all my mosfets, and I wanted to test my voltage on my Vdimm before I upgraded my ram to 4000 VX. When I was using the probe I tried to push it underneath the copper heatsink and it came loose, so I pulled( oops). I know had the Mosfet dangling by one leg, split in half. I didn't power the computer on, I didn't want to risk anything. I know have to find a Mosfet for this motherboard. The Mosfet is made by a company located in China, of course, by a company named APEC or Advanced Powered Electronics C. The mosfet model number is AP9918H I've found it on their website, and I'm sad to report that it costs about a few bucks for the actual component, and 150 dollars to ship. Is there any possible subsitute, or do I have to keep looking for a used/dead motherboard.( somone can point me in the right direction and I've tried Ebay already). I'm really not looking to upgrade, since I just upgraded my ram 2 days ago, and my CPU about 4 months ago. I've had lots of experience working on motherboards, and I'm just interested in getting that one part. I've looked into other motherboards so that I might scrap the MOSFET.

I was also wondering if possible to get a simlar MOSFET with the same values. But having no past experience it's really difficult to pin point the exact typ that I need.

Below I have linked the website and the stats of the MOSFET:

http://www.a-power.com.tw/

9918H
TO252, N-MOS, 20V, low gate drive, Rds(on) < 14 m£[ for DDR switching regulator

The page below is more stats on the same website, the model number the MOSFET is labled AP9918H
http://www.a-power.com.tw/products_05.htm

Thanks in advance!
07-23-2005, 12:37 AM
Para

You can search for an equivalent from either Infineon - the IPD06N03 - or Vishay - SUB70N03 - but make sure it's in TO252 or TO263 (SMD) packaging, so you can solder it in place.
On the P4C800, the Vcore switching regulator uses 3 FETs per phase, of which 2 are cascaded towards the load and one goes to +12V. If you ruined one of the pair going to the coil, the board will pretty much work OK, but you'll probably get some more voltage drop in full load. However, if you ruined the FET towards the power supply, you have to look for the ADP3180 controller, find the line to the FET pilot in the defective phase (pins 20-23 on the ADP3180) and ground it.
You'll get a 2-phase power supply instead of 3-phase, and you'll have to say good-bye to any overclocking, but at least you'll have a functional mobo until you find a replacement FET.
07-23-2005, 02:17 AM
mike047

Quote:

Originally Posted by Para

You can search for an equivalent from either Infineon - the IPD06N03 - or Vishay - SUB70N03 - but make sure it's in TO252 or TO263 (SMD) packaging, so you can solder it in place.

HI, What did you use to cross reference these parts? Do you have a link to an online reference chart?

Thanks,
07-23-2005, 08:43 PM
Elder Young

I could be wrong, but I believe the IRFR3706 from International Rectifier should work. Go to digikey.com and do a search for IRFR3706-ND. They're $1.44 each, then they have a $5 charge for orders under $25, then maybe $10 for shipping.

It has the same voltage rating as the one from your board, but it's rated for higher current and power dissipation as well as slightly lower drain to source resistance, which shouldn't be a problem.

The Vishay model that Para suggested can be bought here:
http://www.newark.com/NewarkWebComme...KU=95B4661&N=0
They also have a spec sheet for it. The Infineon model can be found on digikey.com. I agree that these models should work as well so choose whatever you want. You could also see if any of them are available on mouser.com because it might be cheaper than digikey or newark.

Hope this helps.
07-24-2005, 12:47 PM
Para

Quote:

Originally Posted by mike047

HI, What did you use to cross reference these parts? Do you have a link to an online reference chart?

Thanks,

I used to work at the local Asus wholesale company, and studied all the P4C800 boards they imported over 1 year. I was extremely annoyed by the drop in Vcore whenever the CPU went in full load, and searched - in vain - for a revision with better power source.
04-28-2006, 05:43 AM
Johnny Bravo

Sorry to revive this thread, but has anyone tried these suggested MOSFETs? I'm about to get International Rectifier equilivents (IRLR3715) and would like to know if they are suitable for the application. The Gate threshold voltage is alot higher on the IR chips compared to those of the standard ones, is this OK?

John
04-28-2006, 06:24 AM
freecableguy

thats fine, but there are A LOT of different specifications that go into selecting MOSFETs....rarely will you find an "equivalent" MOSFET for replacement, espcially since the circuit's feedback loop and active regulation component selection is tuned for these...

you would be much better off finding the same MOSFET or contacting the manufacture and asking for a "suitable substitute" if its no longer produced.
04-28-2006, 06:47 AM
Johnny Bravo

Too true, the problem is the companies based in the far east and dont seem to have more westernly based outposts. I may try to get engineering samples but I don't hold much hope on that front. We'll see how this pans out.