CURRENT LIMITING CIRCUIT FOR HIGH-SPEED LOW-SIDE DRIVER OUTPUTS

摘要

An FET switching transistor (106) for the solenoid coil (102) of an ABS braking system can switched ON or OFF in no more than substantially 250 ns. A higher current biasing circuit for fast turn on of the FET switching transistor is disconnected when it is necessary to limit the current flowing therethrough, whether during the in-rush current to the solenoid coil or due to a fault in the system. The high speed switching of the FET switching transistor causes ringing of the current through the transistor which causes the current detector circuit (112) to exit the current control mode. A deglitch circuit (138) prevents the current detector from exiting the current control mode, so that a timer can be used to turn off the FET switching transistor before it can be damaged by the heat generated during current limit operation.