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TOOL IDB-ELE-005
Heatsink & junction T

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Engineering tools are available only on desktop screens.

Heatsink & junction T

Junction temperature, required heatsink thermal resistance, and safety margin for a power device.

Thermal stack J → A RSA = —
Tj RJC Case RCS Sink RSA Ta — °C 45 °C
Tj vs power dissipated at chosen Rθtotal
— °C — °C 0 W — W Power → Tj → Tjmax — derate —
Engineering notes

Thermal stack

  • Tj = Ta + P · (RJC + RCS + RSA)
  • Required: RSA ≤ (Tjmax − margin − Ta)/P − RJC − RCS

Sanity checks

  • If RSA required is negative, even an infinite heatsink isn't enough.
  • Natural convection in plastic rarely beats 10–15°C/W on standard heatsinks.

Result

Live