Fault detection circuit
AssigneeMotorola, Inc.
InventorsRoger L. Hollstein, Steven M. Domer, Frederic B. Shapiro
Life of this patent
Estimating the term…
Abstract
A circuit for detecting when a fault condition has occurred includes an input stage responsive to a logic signal supplied to an input of the circuit for providing an output logic signal at an output thereof. An output stage, including a pulldown circuit, responsive to the output logic signal of the input stage, for providing an output logic signal at an output of the circuit. A fault detection circuit coupled to the output of the input stage and to the output stage for forcing the output of the circuit to a predetermined logic state when the pulldown circuit of the output stage is defective.
Claims10
A circuit having an input and an output, comprising:
- an input stage responsive to a logic signal supplied to the input of the circuit for providing an output logic signal at an output thereof;
- an output stage, responsive to said output logic signal of said input stage, for providing an output logic signal at the output of the circuit;
- a pulldown circuit coupled to said output stage for providing proper voltage logic levels at the output of the circuit;
- and
- detection means coupled to said output of said input stage and to said pull down circuit for forcing the output of the circuit to a predetermined logic state responsive to a fault condition occurring in said pull down circuit.
A method of detecting when a fault condition occurs in a pulldown stage of a circuit, comprising the steps of:
- monitoring a voltage at a node of the pulldown stage;
- forward biasing a first transistor when said voltage at said node reaches a predetermined threshold;
- and
- forcing an output of the circuit to a predetermined logic state, said predetermined logic state being indicative of a fault condition occurring in the pulldown stage.
Dependencies are inferred from the claim text.