SLVSAS7D February 2011 – March 2021 DRV8801-Q1
When the voltage on pin SENSE exceeds VTRIP (0.5 V), overcurrent is detected. The RSENSE resistor should be sized to set the desired ITRIP level.
To set ITRIP to 2.5 A, RSENSE = 0.5 V / 2.5 A = 0.2 Ω.
To prevent false trips, ITRIP must be higher than regular operating current. Motor current during startup is typically much higher than steady-state spinning, because the initial load torque is higher, and the absence of back-EMF causes a higher voltage and extra current across the motor windings.
It is beneficial to limit startup current by using series inductors on the DRV8801-Q1 output, as that allows ITRIP to be lower, and it may decrease the system’s required bulk capacitance. Startup current can also be limited by ramping the forward drive duty cycle.