- #1
Wetmelon
- 154
- 1
Hello again
I'm trying to decide on the correct heatsink for my project, but I'm not sure exactly what I'm looking at. On Digikey, each heatsink has values for Thermal Resistivity and Power Dissipation. This is the datasheet information for the MOSFET:
Tj = -55 to +175 C
Rds(on) = .02 ohm
Rjc = .75 C/W
Rcs = .5 C/W
Rja = 62 C/W
I'm driving 40A at 12V, so my power = 40*40*.02 = 32 W
Temperature Rise (Rjc) = .75*32 = 24 C
Temperature Rise (Rcs) = .5*32 = 18 C
Total Temp Rise (Rjc+Rcs) = 18+24 = 42 C
Available Temperature Rise (150-42) = 108 C
Max Thermal Resistivity of Heatsink = 108/32 = 3.75 C/W
Is the Thermal Resistivity the only thing I have to be worried about? I found a suitable heatsink, but it says its power dissipation is only 9W @ 60C.
I'm trying to decide on the correct heatsink for my project, but I'm not sure exactly what I'm looking at. On Digikey, each heatsink has values for Thermal Resistivity and Power Dissipation. This is the datasheet information for the MOSFET:
Tj = -55 to +175 C
Rds(on) = .02 ohm
Rjc = .75 C/W
Rcs = .5 C/W
Rja = 62 C/W
I'm driving 40A at 12V, so my power = 40*40*.02 = 32 W
Temperature Rise (Rjc) = .75*32 = 24 C
Temperature Rise (Rcs) = .5*32 = 18 C
Total Temp Rise (Rjc+Rcs) = 18+24 = 42 C
Available Temperature Rise (150-42) = 108 C
Max Thermal Resistivity of Heatsink = 108/32 = 3.75 C/W
Is the Thermal Resistivity the only thing I have to be worried about? I found a suitable heatsink, but it says its power dissipation is only 9W @ 60C.