CAN receiver wake-up circuit
AssigneeTexas Instruments Incorporated
InventorsTimothy P. Pauletti, John H. Carpenter, Jr., Benjamin L. Amey
Life of this patent
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Abstract
A wake-up circuit for a ECU on a CAN bus utilizes two complementary switching transistors which will turn ON when there is a differential voltage between CANH and CANL which will turn ON the transistors to pass a current which will be mirrored over to create a voltage which will switch a comparator or a Schmitt trigger. The two signals are then ORed together to generate a digital wake-up signal that can be utilized by other on-chip circuitry.
Claims16
A wake-up detector for an electronic control unit (ECU) on a controller area network (CAN) bus comprising:
- a first transistor of a first conductivity type having a gate electrode coupled to an input terminal for a CANH conductor of the CAN bus;
- a second transistor of a second conductivity type having a gate electrode coupled to an input terminal for a CANL conductor of the CAN bus;
- a first current mirror circuit coupled to a source-drain path of the first transistor and having an output coupled to a first constant current source;
- a second current mirror circuit coupled to a source-drain path of the second transistor and having an output coupled to a second constant current source;
- a first detector circuit coupled to a first junction of the first current mirror circuit and the first constant current source;
- a second detector circuit coupled to a second junction of the second current mirror circuit and the second constant current source;
- an OR gate coupled to an output of the first and second detector circuits and generating a wake up signal.
In a controller area network (CAN) having a plurality of electronic control units (ECU) coupled to a CAN bus, a wake-up detector for a physical layer of an ECU comprising:
- an NMOS transistor having a gate electrode coupled to an input terminal for a CANH conductor of the CAN bus;
- a PMOS transistor having a gate electrode coupled to an input terminal for a CANL conductor of the CAN bus;
- a first current mirror circuit coupled to a source-drain path of the NMOS transistor and having an output coupled to a first constant current source, the first constant current source comprising a third current mirror circuit coupled between a first junction and a first voltage source;
- a second current mirror circuit coupled to a source-drain path of the PMOS transistor and having an output coupled to a second constant current source, the second constant current source comprising a fourth current mirror circuit coupled between a second junction and a second voltage source;
- a first Schmitt trigger circuit coupled to a first junction of the first current mirror circuit and the first constant current source;
- a second Schmitt trigger circuit coupled to a second junction of the second current mirror circuit and the second constant current source;
- an OR gate coupled to an output of the first and second Schmitt trigger circuits and generating a wake-up signal.
A method for detecting a signal on a controller area network (CAN) bus for waking-up electronic control unit (ECU) coupled to the CAN bus comprising:
- coupling a CANH conductor of the CAN bus to a first transistor of the first conductivity type;
- coupling a CANL conductor of the CAN bus to a second transistor of a second conductivity type;
- coupling an output of the first transistor to a first current mirror circuit and an output of the second transistor to a second current mirror circuit, the current mirror circuits mirroring current in source-drain paths of the of the respective transistors;
- comparing an output of the first current mirror circuit to a first constant current source to generate a first comparator signal;
- comparing an output of the second current mirror circuit to a second constant current source to generate a second comparator signal;
- and
- generating a wake-up signal if either of the first or the second comparator signals equals or exceeds a predetermined level.
Dependencies are inferred from the claim text.