Power losses and thermal design

AN3303

20/27

Doc ID 18164 Rev 2

Considering now the case with SR: again the thermal rise is 65 °C. Based on the power

dissipation per MOSFET calculated in Equation 8, the maximum junction-to-ambient

thermal resistance allowed is:

Equation 14

That means that a heatsink is not required, just some copper area is needed, calculated

according to the SRK2000 datasheet indication.

The same is true for the SRK2000:

Equation 15

This is higher than the controller junction-to-ambient thermal resistance (150 °C/W).

R

th j

amb

–

()

65

°C

P

MOS

---------------

245

°CW

⁄

=

=

R

th j

amb

–

()

65

°C

P

SRK2000

-------------------------

409

°CW

⁄

=

=