MC33486 Motorola, MC33486 Datasheet - Page 8

• Manufacturer Part Number: MC33486
• Description: Dual High Side Switch
• Manufacturer: Motorola

total power dissipation is : 0.04*8*8 = 2.56W
Assuming an 85°C ambient temperature, the junction temperature is a t : 85 + 55 = 140°C.
be taken into account. Or an additional thermal resistance from inside module to external ambient temperature must be added.
The calculation method remains the same.
junction to ambient thermal resistance follows the same rules as for the high side block, and is in the same range.
The use of this model is similar to the electrical Ohm law (voltage = resistance X current), where:
. Voltage represents temperature
. Current represents power dissipated by the device
. Resistance represents thermal resistance.
We finally got :
Temperature or delta temperature = Power Dissipation times Thermal resistance, that is : °C = W ° x C/W.
Any node temperature can easily be calculated knowing the amount of power flowing through the thermal resistances.
Example :
1. Numerical value.
. Junction to case thermal resistance : 2°C/W (Rthjc)
. Power into the switch : assuming the device is driving 8amps at 150°C junction temperature (Rdson at 150°C is 40mΩ) the
. Case to ambient thermal resistance (Rthca) : 20°C/W
2. Results.
. Junction to case delta temp : 5°C (2.5W x 2°C/W)
. Case delta temp from ambient : 50°C (20°C/W x 2.5W)
. Actual junction temperature node will be :
50°C + 5°C = 55°C above the ambient temperature.
The above example take into account the junction to ambient thermal resistance, assuming that the ambient temp is 85°C.
In the case where the device plus its printed circuit board are located inside a module, the ambient temp of the module should
The low side block is packaged into D
Dual High Side Switch for H-Bridge Automotive Applications
Freescale Semiconductor, Inc.
For More Information On This Product,
2
PAK or DPAK package. Thermal resistance junction to case is approx. 2°C/W. The
Go to: www.freescale.com
MC33486
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