Mosfet Advice

[Green Probe]

Hi, Im looking to replace some EMP21N03 mosfets on an Alienware motherboard, but I'm having trouble finding a legit supplier. The ones that are available from China have pictures with the engraved logo looking very scratchy and sketchy. Nobody in the US sells them. I'm trying to find a compatible mosfet, but I'm not well versed enough to be confident im making the right choice. Does anyone have a suggestion or advice that could help me find the right mosfet? Thanks!

[mon2]

This is pretty much jellybean part and does not have to be the same as the original. Digikey / Mouser / Arrow should have valid replacements. TI website may even offer free samples of their version.

To replace this part:

< suggest order of requirements >

a) be the same style of mosfet - this is a single mosfet in a package
b) be the same N-channel or P-channel type. Yours is N-channel type.
c) be the same physical size to make it easier to replace the original. Yours is ~6 x 6mm in body size.
d) be able to handle the voltage of ~30v between source / drain pins. Very common on motherboards.
e) be able to handle the peak current - this may be the only real concern but not impossible to find or exceed.

TI # CSD18510Q5B
https://www.ti.com/product/CSD18510Q...buy&#samplebuy
* looks like a good sub for the original and is able to handle even high currents but only available through TI webstore

The following is also suitable and more readily available:

CSD18563Q5A

https://www.mouser.ca/ProductDetail/...gaAqnLEALw_wcB

[Green Probe]

Thank you kindly, mon2! You're a legend as always.

[mon2]

Here is another one that looks to be promising - what I like about this one is a lower logic level enable threshold (like the original one you are replacing):

STL160N6LF7

https://www.mouser.ca/ProductDetail/...aBnx2pdA%3D%3D

You should be able to find the same from Digikey, etc. The part is from ST Semiconductor.

[Green Probe]

I just ordered some CSD18563Q5A. Should I use STL160N6LF7 instead? It is to replace the first two parallel mosfets where DC power comes into the board. I don't mind having some spare mosfets around, I just wish I could add it to my existing order for shipping lol.

[mon2]

I think either is ok. If all about specs, the ST can handle even higher currents. If you can add to the order, does not hurt to throw in the ST part as a spare.

[Green Probe]

I was able to contact Mouser's customer support and get some ST parts as well. Thank you again, mon2. I'm still using the Alienware m15 r5 you helped me fix by the way!

[mon2]

Awesome! Hope this repair works for you. On paper, the mosfets look good to me. In general, we have more faith on major branded parts like the ones you have ordered as compared to offshore local China brands. Seriously cannot knock their (China) innovations - we are reviewing a mix of their AI / FPGA and extremely low cost (ie. $0.10 USD) microcontrollers. They are kicking in the semiconductor industry and are serious on design wins. The truth is that end customers want the 'best' and want to pay the least.

[Green Probe]

Is Excelliance small brand? I feel like I've seen their logo before. Dell seems to think they're good enough to put in Alienwares. Serendipitously I'm now working on an Alienware m17 r5 that got some liquid into it that smoked the DC-IN mosfets. Can't blame the mosfets for that lol.
Are you going to do a public writeup about their new tech, or are the reviews for private use?

[mon2]

We design & build products for the PC industry and for many OEMs including Dell / HP, Foxconn, blah blah. Have been to Asia for many years and met many brands that are not really known here. They literally will jump you as you walk through the industry fairs if you are not a local. I think it is because they can charge higher margins. Last fall tried to find Master Liu (without alerting him of my visit) and was just blown away by the synergy in Shenzhen. I will post a few pics here. Tons of electronic stores selling everything you can imagine and all concentrated with blocks of each other. Many of the widgets we use at consumer level are contracted out to design houses in Asia. Once in a while, we get lucky and get thrown a bone. Based on their budget, the designer will use brands like you have faced instead of say TI, Infineon, etc. that are often higher grade but more expensive than the brands in Asia. Not stating that all vendors are evil overseas and many are worthy of being used. Sad truth is that we will pay 'tourist' prices for parts that are being purchased out Asia. Mind you, their (China) government subsidizes their sales so often dumping goods into the USA / Canada / Europe markets. Have seen it when I was in Taipei, Taiwan. We witnessed that their local computer stores were selling an add-on adapter for ~30$ USD yet in North America - the same is ~6$ USD.

On the review, yes, I do post on many other forums but you can find the same if that interests you.

Here are some links to get you started if you wish to R&D on microcontrollers. Some amazing (free) toolchains to program these in C language.

These are very low cost RISC-V microcontrollers that are $0.10 USD in volume but still super cheap in small qty. Full development kits are under $10 USD.

https://www.cnx-software.com/2025/04...e-5-0-usb-2-0/

https://github.com/openwch/ch570

https://www.youtube.com/watch?v=Yt7GLgWr2jY

https://www.youtube.com/watch?v=KIz0jpzJiIo

If you are interested in other digital design / FPGA topics, can share more info / links.