Hello,
I'm working with this MOSFET:
http://www.es.co.th/Schemetic/PDF/IRF640N.PDF
This datasheet shows us about thermal resistance in the bottom of page 2. I need this MOSFET to be operated at (Pd)150W dissipation power and its junction temperature(Tj) to be 100 celsius. Ambient temperature(Ta) is 50 celsius so I have to calculate the thermal resistance from junction to ambient (θja) first and then the case to ambient thermal resistance (θca)
so the equation is Tj=Ta+ θja*Pd
substitutes all those stuff, and you'll get θja= 0.333 celsius/W....... seems to be fine
From the datasheet we have θjc=1.0
θca= θja-θjc = 0.333-1.0=-0.667 celsius/W OMG!!!
1) Did I do anything wrong about calculation?
2) Did I misunderstand something in the datasheet?
3) Is this an impossible case?
I'm working with this MOSFET:
http://www.es.co.th/Schemetic/PDF/IRF640N.PDF
This datasheet shows us about thermal resistance in the bottom of page 2. I need this MOSFET to be operated at (Pd)150W dissipation power and its junction temperature(Tj) to be 100 celsius. Ambient temperature(Ta) is 50 celsius so I have to calculate the thermal resistance from junction to ambient (θja) first and then the case to ambient thermal resistance (θca)
so the equation is Tj=Ta+ θja*Pd
substitutes all those stuff, and you'll get θja= 0.333 celsius/W....... seems to be fine
From the datasheet we have θjc=1.0
θca= θja-θjc = 0.333-1.0=-0.667 celsius/W OMG!!!
1) Did I do anything wrong about calculation?
2) Did I misunderstand something in the datasheet?
3) Is this an impossible case?