CAN RECEIVER WAKE-UP CIRCUIT
First Claim
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1. A wake-up detector for an electronic control unit (ECU) on an controller area network (CAN) comprising:
- a first transistor of a first type conductivity having a gate electrode coupled to an input terminal for a CANH conductor of a CAN bus;
a second transistor of a second type conductivity having a gate electrode coupled to an input terminal for a CANL conductor of a 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 detectors and generating a wake up signal.
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Abstract
A wake-up circuit for a ECU on a ECN 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.
26 Citations
16 Claims
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1. A wake-up detector for an electronic control unit (ECU) on an controller area network (CAN) comprising:
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a first transistor of a first type conductivity having a gate electrode coupled to an input terminal for a CANH conductor of a CAN bus;
a second transistor of a second type conductivity having a gate electrode coupled to an input terminal for a CANL conductor of a 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 detectors and generating a wake up signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. In a controller area network (CAN) having a plurality of electronic control units (ECU) coupled to a bus, a wake-up detector for a physical layer of an ECU comprising:
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a NMOS transistor having a gate electrode coupled to an input terminal for a CANH conductor of a CAN bus;
a PMOS transistor having a gate electrode coupled to an input terminal for a CANL conductor of a 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.
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14. A method for detecting a signal on a controller area network (CAN) bus for waking-up electronic control unit (ECU) coupled to the bus comprising:
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coupling a CANH conductor of the CAN bus to a first transistor of the CAN bus to a first transistor of the first type;
coupling a CANL conductor of the CAN bus to a second transistor of a second 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;
comparing an output of the second current mirror circuit to a second constant current source; and
generating a wake-up signal if either comparing step equals of exceeds a predetermined level. - View Dependent Claims (15, 16)
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Specification