The VS/VSINT overvoltage brake is intended to protect the application, when a motor operates in generator mode. The operation in generator mode can occur in several cases such as: - The motor rotation is caused by the application of an external torque, such as the manual closure of the trunk lid or of a sliding door - While the motor is activated by the half-bridges, then the MOSFETs are turned off without any active brake
In both cases, a current flows through the motor while the external half-bridges are off.
The motor current flows through the body diode of the external MOSFETs. If the charge pump is off, then the current cannot flow back to the battery. Instead, it charges the DC link capacitor, causing an increase of the VS voltage. If no measures are taken, VS can exceed the absolute maximum rating of some components, causing a damage of the module.
The VS/VSINT overvoltage brake feature monitors VS/VSINT, and turns on the low-side MOSFETs, even if the device is in sleep mode or if the charge pump is off. This action actively brakes the motor and stops the increase of the supply voltage, protecting the module.