STK6103

No. 4290- 10/11

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Thermal radiation design

Actual thermal radiation design requires determination of the IC internal average power dissipation Pd from the

motor phase current Io (Fig. 9). Pd is then used to determine the thermal resistance for the radiator from the

following expression.

θc – a = Tc max – Ta (°C/W)

Pd

where Tc max = 105°C

Ta = ambient temperature

With a 2.0 mm radiation plate, the required area can be determined from Fig. 10. Note that substrate temperature

will vary widely with set internal air temperature, and Tc for the mounted state must be 105°C max.