SLVSC40H June 2013 – May 2020 DRV8711
PRODUCTION DATA.
Overcurrent is sensed by monitoring the voltage drop across the external FETs. If the voltage across a driven FET exceeds the value programmed by the OCPTH bits in the DRIVE register for more than the time period specified by the OCPDEG bits in the DRIVE register, an OCP event is recognized. When operating in direct PWM mode, during an OCP event, the H-bridge experiencing the OCP event is disabled; if operating in indexer mode, both H-bridges will be disabled. In addition, the corresponding xOCP bit in the STATUS register is set, and the FAULTn pin is driven low. The H-bridge(s) will remain off, and the xOCP bit will remain set, until it is written to 0, or the device is reset.
In order to calculate the current needed to trip OCP, use the OCPTH value and the FET RDS(ON):
If the motor winding parasitic capacitance, CL, is very large (on the order of 1 µF), then it may be required to increase OCPDEG to account for the large inrush current. For CL less than 10 nF, the default value for this register should be sufficient.