Alan B wrote: ↑
Nov 20, 2017 3:30 pm
I'm not convinced these parts are that inconsistent, unless they are counterfeit knockoffs which are common.
Many people do not use proper static control and damage these static sensitive parts while handling them. Static damaged parts may work for awhile and then fail later.
You only need 6 matched pairs for a 12 FET controller. The pairs can be different, just the two in parallel should be well matched. If they all come from the same batch they may be fairly well matched already.
I made 2 orders from Verical/Arrow. I just went back and looked at my order history. I buy from Digi-key as well so I was confused until I looked at my past invoices just now. One order was in March 2017 (qty 30) and the other was in May 2017 (qty 40). Anyway, both companies are pretty legit...so I doubt they are fake mosfets.
I have had results while testing AOT290's that vary a lot. For example I have never had Vgs(th) be lower than 3.4 volts despite the minimum being 2.9 volts. 3.6 volts was common in my first batch, but I had several that were 4.1 or 4.2 volts too. Just about all of the second batch have a Vgs(th) of 4.1 to 4.3 volts which is the max or higher and none were at or near the typical rating.
In the product summary it says: RDS(ON) (at VGS=10V) < 3.5 micro ohms. further down in the actual spec section, it says typical is 2.5 and max is 3.2, but I've had quite a few that are well over 3.5 micro ohms. The specs for the AOT290 look great, but consistency and actual product matching up with the specs has been less than spectacular. I've never scrutinized a mosfet as much as I have the AOT290 so I can't speak from experience if this is typical or not. I'm just saying, I want to try something else...aka the IXFP180N10T2 and scrutinize it like I have the AOT290. It costs a dollar more per mosfet. It had better be at least a more consistently similar mosfet!