JAJSSO2 December 2023 MCF8315C
PRODMIX
The power dissipated in the output FET resistance (RDS(on)) dominates power dissipation in MCF8315C.
At start-up and fault conditions, the FET current is much higher than normal operating FET current; remember to take these peak currents and their duration into consideration.
The total device power dissipation is the power dissipated in each of the three half-bridges added together along with standby power, LDO and buck regulator losses.
The maximum amount of power that the device can dissipate depends on ambient temperature and heatsinking.
Note that RDS(on) increases with temperature, so as the device heats, the power dissipation increases. Take this into consideration when sizing the heatsink.
A summary of equations for calculating each loss is shown below in Table 9-1.
Loss type | MCF8315C |
---|---|
Standby power | Pstandby = VM x IVM_TA |
LDO | PLDO = (VM-VAVDD) x IAVDD, if BUCK_PS_DIS = 1b PLDO = (VBK-VAVDD) x IAVDD, if BUCK_PS_DIS = 0b |
FET conduction | PCON = 3 x (IRMS(FOC))2 x Rds,on(TA) |
FET switching | PSW = 3 x IPK(FOC) x VPK(FOC) x trise/fall x fPWM |
Diode | Pdiode = 3 x IPK(FOC) x Vdiode x tdead x fPWM |
Buck | PBK = 0.11 x VBK x IBK (ηBK = 90%) |