MSK4804 M. S Kennedy, MSK4804 Datasheet - Page 3

• Manufacturer Part Number: MSK4804
• Description: 1200v/100a Sic Half Bridge
• Manufacturer: M. S Kennedy

THERMAL CALCULATIONS
PWM duty cycle and switching frequency all factor into power dissipation. DC losses or "ON-TIME" losses are simply
V
30%, DC losses equal TBD watts. Switching losses vary proportionally with switching frequency. The MSK 4804 typical
switching losses at V
the turn-off switching loss. Multiplying the switching frequency times the switching losses will result in a power dissipation
number for switching. The MSK 4804, at 5KHz, will exhibit switching power dissipation of TBD watts. The total losses are
the sum of DC losses plus switching losses, or in this case, TBD watts total.
TBD watts x 0.190°C/W thermal resistance equals TBD degrees of temperature rise between the case and the junction.
Subtracting TBD°C from the maximum junction temperature of 150°C equals TBD°C maximum case temperature for this
example.
DS
Maximum junction temperature - junction temperature rise = maximum baseplate temperature
V
Turn-on switching loss + Turn-off switching loss = Total switching losses = TBD + TBD = TBDuJ
Total switching loss x PWM frequency = Total switching power dissipation = TBDuJ x 5KHz = TBD watts
Total power dissipation = DC losses + switching losses =TBD + TBD = TBD watts
Junction temperature rise above case = Total power dissipation x thermal resistance
Power dissipation and maximum allowable temperature rise involve many variables working together. Drain current,
APPLICATION NOTES
DS
x Drain Current x PWM duty cycle. For the MSK 4804, V
150°C - TBD°C = TBD°C
TBD watts x 0.190°C/W = TBD°C temperature rise above case
x I
D
x PWM duty cycle = TBD x 100 amps x 30% =TBD watts DC losses
DS
=600V and I
DS
=100A are about TBDuJ, which is simply the sum of the turn-on switching loss and
3
DS
=TBD max., and at 100 amps and a PWM duty cycle of
PRELIMINARY
Rev. A 1/10