- #1

KyleGranger

- 37

- 2

- TL;DR Summary
- I would like to calculate parameters, such as power dissipation, for a given MOSFET based on the manufacturers datasheet.

I would like to be able to determine the current through a device for a given junction temperature. I am looking at a datasheet and notice that it gives the device power dissipation with different case temperatures. Since the maximum junction temperature is 175 C, I believe that means that lower case temperature with higher power means it would require a better cooling system compared to higher case temperature and lower power dissipation.

First I wanted to calculate the power dissipated by the device for a given case temperature, assuming the junction temperature is 175 C. To do this, I thought I would use the equation q=ΔT/Rth where q represents the power in watts, ΔT represents the temperature in degrees C, and Rth represents the thermal resistance C/W.

I checked this logic using the datasheet values for P=441 W @ Tc=25 C and Rth=0.25 C/W. I get (175-25)/0.26 = 577 W. The datasheet value is 441 W, so this method doesn't check out. What am I missing here? Or is there a better way to do this?

What I hope to do next is determine the number of parallel devices for a given cooling system at a given current. This part will be done using thermal simulations, but I need to know a power to apply as a heat source and have a way to check my basic simulations to ensure I'm getting close to the expected case temperature.

A link to the datasheet is below.

https://unitedsic.com/datasheets/DS_UF3C065030K3S.pdf

First I wanted to calculate the power dissipated by the device for a given case temperature, assuming the junction temperature is 175 C. To do this, I thought I would use the equation q=ΔT/Rth where q represents the power in watts, ΔT represents the temperature in degrees C, and Rth represents the thermal resistance C/W.

I checked this logic using the datasheet values for P=441 W @ Tc=25 C and Rth=0.25 C/W. I get (175-25)/0.26 = 577 W. The datasheet value is 441 W, so this method doesn't check out. What am I missing here? Or is there a better way to do this?

What I hope to do next is determine the number of parallel devices for a given cooling system at a given current. This part will be done using thermal simulations, but I need to know a power to apply as a heat source and have a way to check my basic simulations to ensure I'm getting close to the expected case temperature.

A link to the datasheet is below.

https://unitedsic.com/datasheets/DS_UF3C065030K3S.pdf