SLVAFT0 July 2024 DRV8706-Q1 , DRV8714-Q1 , DRV8718-Q1
Based on these real-world observations, we modify the ideal general guideline given previously to account for the non-ideal characteristics of the capacitor:
Where:
CBULK is the bulk capacitance
k is a scale factor to account for the ESR for typical capacitors in this type of application; based on the lab measurements above with DRV8718 EVM, k of about 3 is practical for these cases.
ΔIMOTOR is the expected variation in motor current, imax – imin
TPWM is the PWM period which is the reciprocal of the PWM frequency
ΔVSUPPLY is the allowable variation in the motor supply voltage
Figure 3-7 plots several data points and applies this general guideline, showing relatively good agreement.