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## Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?

Level 2
Level 2
Hi， I am using MOSFET to control PMSM，and I have a question，Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?
1 Solution

## Re: Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?

Moderator
Moderator

Hi,

Thank you for posting on the Infineon community.

The case temperature or the drain pad temperature must be measured in order to get the junction temperature based on the following equation,

Tj - Tc / Rthjc = Pd

Regards,
Abhilash P

3 Replies

## Re: Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?

Moderator
Moderator

Hi,

Thank you for posting on the Infineon community.

The case temperature or the drain pad temperature must be measured in order to get the junction temperature based on the following equation,

Tj - Tc / Rthjc = Pd

Regards,
Abhilash P

## Re: Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?

Level 2
Level 2

Thanks，@Abhilash P，but I still don't know the equation，Tj - Tc / Rthjc = Pd，what does the means of Tj、Tc、Rthjc、Pd?

## Re: Do I need calculate internal temperature of MOSFET based on surface temperature of PCB board?

Moderator
Moderator

Hi,

Tj : Junction temperature
Tc :  Case temperature
Pd : Power dissipated.
Rthjc: Junction to case thermal resistance.

Regards,
Abhilash P