I think it’s very optimistic. The SOA chart suggests that. As always you have to read the entire data sheet.
Aye, 'twas always the way. Once you get above ~10-20% of the rated V
ce or V
ds of a device the SOA limited power dissipation of a device plumets way below the headline figure from the front page of the datasheet, and that's typically at 25ºC T
c before you've derated the device for a realistic operating temperature.
Case in point I was looking at yesterday: FDH055N15A power MOSFET. Datasheet figures, front page: 150 V, 167 A, second page P
D 429W (T
c = 25ºC). Look at the DC SOA at V
ds=30V => I
ds = ~2.1A, therefore P
D = 63W only 15% of the headline power figure at 20% of the headline V
DS and 1.2% of the headline I
DS figure, and that's
before derating for operating temperature.
Let's just see those figures side by side:
Claim - 150 V, 167 A, 429W.
Actual - 30V, 2.1A, 63W.
The front page (or two) of a datasheet is basically lies made up by the marketing department.
(And yes, I confess, looking at chunky MOSFETs is a tacit admission that I'm looking at doing a DC Electronic Load design, again.)