Dear Team,
Our application is Vin 3v3 Vout 12v,FSW set to high and output L is 4.7uH ,but when the load is higher than 0.12A Vout will drop to 9V,our test point is closed to the output side,is there any reason that might affect the Vout drop issue?
Many Thanks,
Jimmy
Hi Jimmy,
I think the current limit is triggered.
Ton=D*Ton=0.725*(1/1.2MHz)=0.6us, Iin=0.12A*12V/(0.83*3.3)=0.53A, considering the inductor current ripple=Vin*Ton/L=0.42A, so inductor peak current can be up to 0.53+0.42/2=0.74A.
According to the current limit vs. duty cycle figure, when duty cycle is 72.5%, current limit is around 0.75A. So the current limit is triggered at that state.
Regards,
Bryce
