CAN bus termination circuits and CAN bus auto-termination methods
First Claim
Patent Images
1. A CAN bus termination circuit comprising:
- a first circuit in electrical communication with a CAN bus and configured to monitor an electrical operating parameter associated with operation of the CAN bus, the electrical operating parameter being associated with whether or not a power on signal has been generated by one node connected with the CAN bus for a next-in-line node connected with the CAN bus; and
a second circuit in electrical communication with the first circuit, the second circuit being selectively enabled by the first circuit responsive to the first circuit'"'"'s sensing a change in the electrical operating parameter that it is configured to monitor, the second circuit being configured to terminate the CAN bus when it is enabled.
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Abstract
CAN bus termination circuits, and CAN bus auto-termination methods are described. In one embodiment, a CAN bus termination circuit includes a first circuit in electrical communication with a CAN bus. The first circuit is configured to monitor an electrical operating parameter associated with operation of the CAN bus. A second circuit is in electrical communication with the first circuit, and is selectively enabled by the first circuit responsive to the first circuit'"'"'s sensing a change in the electrical operating parameter that it is configured to monitor. When enabled, the second circuit terminates the CAN bus.
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Citations
19 Claims
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1. A CAN bus termination circuit comprising:
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a first circuit in electrical communication with a CAN bus and configured to monitor an electrical operating parameter associated with operation of the CAN bus, the electrical operating parameter being associated with whether or not a power on signal has been generated by one node connected with the CAN bus for a next-in-line node connected with the CAN bus; and
a second circuit in electrical communication with the first circuit, the second circuit being selectively enabled by the first circuit responsive to the first circuit'"'"'s sensing a change in the electrical operating parameter that it is configured to monitor, the second circuit being configured to terminate the CAN bus when it is enabled. - View Dependent Claims (2, 3, 4, 5, 6, 7)
a current-sensing circuit that is configured to sense an operating current associated with operation of the CAN bus; and
a switching circuit that is configured to selectively incorporate the second circuit responsive to sensing the change in the electrical operating parameter.
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5. The CAN bus termination circuit of claim 1, wherein the second circuit comprises a signal reflection-reducing circuit.
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6. The CAN bus termination circuit of claim 1, wherein the second circuit comprises a resistive circuit.
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7. The CAN bus termination circuit of claim 1, wherein:
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the first circuit comprises;
a current-sensing circuit that is configured to sense an operating current associated with operation of the CAN bus; and
a switching circuit that is configured to selectively incorporate the second circuit responsive to sensing the change in the electrical operating parameter; and
wherein the second circuit comprises a signal reflection-reducing circuit.
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8. A CAN bus system comprising:
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a CAN bus;
a plurality of nodes distributed along and operably connected with the CAN bus;
a power-on signal generation circuit having an output line that is coupled with the plurality of nodes and configured to enable the nodes; and
for each node;
a termination circuit connected to the output line and being configured to monitor for whether one node on the CAN bus has enabled a next-in-line node on the CAN bus, and responsive to sensing that the one node has not enabled the next-in-line node, terminate the CAN bus. - View Dependent Claims (9, 10, 11, 12, 13)
a current-sensing circuit that monitors current flow through the output line; and
a switchable signal-reflection-reducing circuit connected with the current-sensing circuit and configured to be selectively switched by the current-sensing circuit when the current-sensing circuit senses a predetermined current magnitude through the output line, the switchable signal-reflection reducing circuit being configured to, upon termination of the CAN bus, reduce signal reflection in the CAN bus.
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12. The CAN bus system of claim 8, wherein the termination circuit comprises a switchable signal-reflection-reducing circuit having a resistive element configured to, upon termination of the CAN bus, reduce signal reflection in the CAN bus.
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13. The CAN bus system of claim 8, wherein:
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the CAN bus has first and second signal-carrying lines; and
the termination circuit comprises;
a switching circuit connected with the first and second signal-carrying lines and having an output;
a resistive circuit connected with the output of the switching circuit, the resistive circuit being configured to reduce signal reflection in the first and second signal-carrying lines; and
a current-sensing circuit connected with the switching circuit that monitors current flow through the output line, and further wherein the current-sensing circuit is configured to switch the switching circuit between an enabled state that incorporates the resistive circuit, and a disabled state that does not incorporate the resistive circuit.
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14. A CAN bus auto-termination method comprising:
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monitoring an electrical operating parameter associated with operation of at least one CAN bus node of a CAN bus, said electrical operating parameter being associated with whether the one CAN bus node has generated a signal that enables a next-in-line CAN bus node; and
terminating the CAN bus, responsive to the one CAN bus node not generating a signal that enables the next-in-line CAN bus node. - View Dependent Claims (15, 16, 17, 18, 19)
said monitoring comprises monitoring an electrical operating parameter associated with operation of a plurality of parallel-connected CAN bus nodes; and
said terminating comprises enabling a circuit that is configured to reduce signal reflection in the CAN bus.
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19. The method of claim 14, wherein:
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said monitoring comprises monitoring an electrical operating parameter associated with operation of a plurality of parallel-connected CAN bus nodes; and
said terminating comprises incorporating a resistive element with the at least one CAN bus node.
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Specification