Current sense circuit for motor drive

DSON A small capacity FET is coupled to a power MOSFET to sense voltage across the power MOSFET for determining current carried through the power MOSFET. The FET is turned on when the power MOSFET is turned on to obtain a sense voltage that is fed to a comparator to determine if the voltage across the power MOSFET exceeds a threshold voltage. The output of the comparator is used to shut off the drive for the power MOSFET if the threshold is exceeded. The voltage across the FET can be used with a temperature sense and knowledge of the FET Rto obtain a sense feedback of current through the power MOSFET. The FET is controlled with a delay to turn on after the power MOSFET is turned on, and turns off before the power MOSFET turns off.