ZHCSOK3 august 2023 BQ25756
PRODUCTION DATA
Higher switching frequency allows the use of smaller inductor and capacitor values. Inductor saturation current should be higher than the inductor current (IL) plus half the ripple current (IRIPPLE):
The inductor ripple current in buck operation depends on input voltage (VAC), duty cycle (DBUCK = VBAT/VAC), switching frequency (fSW) and inductance (L):
During boost operation, the duty cycle is: DBOOST = 1 – (VAC/VBAT). The inductor ripple current is:
The maximum inductor ripple current happens with D = 0.5 or close to 0.5. Ripple calculations should be analyzed for both forward and reverse operating modes if applicable.
Usually inductor ripple is designed in the range of (20 – 40%) maximum inductor current (in either forward or reverse mode) as a trade-off between inductor size and efficiency for a practical design.