Lower Voltage FET's, IRFB3077PBF vs FDP027N08B_F102 vs ???

[HypnoToad]

3077 spec:
http://www.irf.com/product-info/datasheets/data/irfb3077pbf.pdf

FDP027N08B spec:
http://www.fairchildsemi.com/ds/FD/FDP027N08B.pdf

As you can see, they are pretty similar specs, the FDP027N08B has a lower RDSon which I'm lead to believe is the most important thing to keep low. 2.7mOhm vs 3.3mOhm.

Now I'm looking to replace 6 blown STP75NF75 FET which have a high RDSon of 11mOhm with better quality FET's. Now, I see the irfb3077 gets a lot of recommendations on here but is there any reason to choose it over the FDP027N08B?

Both IC's are very similarly priced and are in stock in the UK, so which one should I go for? I won't be going above 55v input voltage.

Thanks.

 

[Jeremy Harris]

Those Fairchild FETs look slightly better than the IR ones, good find. The important criteria are the gate to source max voltage (Vdss), Rdson and the total gate charge, Qg(tot), and the Fairchild FETs are better than the 3077s by a small margin, with a lower total gate charge, higher Vdss and lower Rdson. Id is the same for both and is a package limit. The only slight niggle is the higher thermal resistance for the Fairchild FETs, 0.61 deg C/W against 0.402 deg C/W for the 3077s. In practice this probably doesn't matter, as the lower Rdson and Qg(tot) should mean both lower I²R losses and faster switching (so lower switching losses).

 

[HypnoToad]

Thanks, I must admit a lot of the stuff in the spec sheet went way over my head, but if the specs are good then I'll order some. I guess the higher thermal package resistance of the Fairchild FETs also explains why the power dissipation is lower also, but I don't plan on trying to pull a crazy amount of current on my setup so I'm sure I'll be OK.

Also I should mention that they are actually coming from the US, I didn't realise Mouser worked this way until I got to the checkout page, so the 3077 is a good option still if you need to source it from RS or Farnell in the UK.