Controller area network (CAN), CAN device and method therefor

1. A Controller Area Network, CAN, device, the CAN device comprising:

a CAN transmitter connected to two CAN bus terminals of the CAN device;

a receiver circuit operably coupled to the two CAN bus terminals of the CAN device; and

a controller connected to the CAN transmitter, wherein the controller is configured to:

determine whether the CAN device is operating as a transmitter node or a receiver node;

detect a transition of the CAN device from a dominant state to a recessive state; and

in response to both detecting a transition of the CAN device from the dominant state to the recessive state, and the determination of whether the CAN device is operating as a transmitter node or a receiver node, control an output impedance of the CAN transmitter to be within an impedance value range at the dominant state whilst a differential driver voltage on a CAN bus connected to the CAN device decreases to a predefined voltage.

2. The CAN device of claim 1 , wherein the controller is an impedance controller and the transmitter is an impedance bridge.

3. The CAN device of claim 2 , wherein the impedance controller connected to the CAN transmitter is configured to provide a control of the output impedance of the impedance bridge to be within a first predefined impedance value range in a feedforward manner when the CAN device is operating as a transmitter node and configured to provide a control of the output impedance of the impedance bridge to be within a second predefined impedance value range when the CAN device is operating as a receiver node.

4. The CAN device of claim 2 , wherein the impedance bridge comprises two legs, and wherein each of the two legs comprises an adjustable pull circuit and an adjustable push circuit connected in series between a common voltage supply rail and a common ground rail and to each of the two CAN bus terminals.

5. The CAN device of claim 1 , wherein the controller is further configured to:

increase the output impedance of the CAN transmitter to be within a threshold of a range of a characteristic impedance of the CAN bus whilst the differential driver voltage on the CAN bus is maintained at a predefined voltage level; and

subsequently, increase the output impedance of the CAN transmitter from the characteristic impedance of the CAN bus to a high ohmic value whilst the differential driver voltage on the CAN bus is maintained at the predefined voltage level.

6. The CAN device of claim 1 , wherein the controller is further configured to increase the output impedance of the CAN transmitter to be within an impedance value range of a characteristic impedance of the CAN bus before a data sample point whilst a differential driver voltage on the CAN bus is maintained at the predefined voltage level.

7. The CAN device of claim 1 further comprising a time window filter circuit operably coupled to the receiver circuit and the controller and configured to determine whether the CAN bus voltage had been above a threshold for a period of time, and in response thereto provide an indication to the controller that the CAN device is operating as a receiver node.

8. The CAN device of claim 7 wherein the time window filter circuit is further configured to filter noise from a receive data signal from the receiver circuit.

9. The CAN device of claim 7 wherein the time window filter circuit is a window logic circuit coupled to a bit timing logic circuit configured to reject an output of the receiver circuit other than for a dominant to recessive transition.

10. The CAN device of any of claim 7 further comprising at least one of:

a baudrate detector circuit configured to measure a bit rate employed by the CAN device and provide the measured bit rate to the controller;

a serial-to-parallel interface, SPI, configured to provide a predetermined employed bit rate to the controller.

11. A Controller Area Network, CAN, comprising a CAN device according to any of claim 1 .

12. A method for ringing suppression in a Controller Area Network, CAN, device, the method comprising:

determining whether the CAN device is operating as a transmitter node or a receiver node;

detecting a transition of the CAN device from a dominant state to a recessive state; and

in response to detecting both a transition of the CAN device from the dominant state to the recessive state and the determination of whether the CAN device is operating as a transmitter node or a receiver node, controlling an output impedance of the CAN transmitter to be within an impedance value range whilst a differential driver voltage on a CAN bus connected to the CAN device decreases to a predefined voltage.

13. The method of claim 12 , further comprising providing a control of the output impedance of a CAN transmitter to be within a first impedance value range in a feedforward manner when the CAN device is operating as a transmitter node and providing a control of the output impedance of the CAN transmitter to be within a second predefined range in a feedback manner when the CAN device is operating as a receiver node.

14. The method of claim 13 , further comprising determining whether the CAN bus voltage had been above a threshold for a period of time, and in response thereto providing an indication to a controller that controls the output impedance of the CAN transmitter to be within the second predefined range when the CAN device is operating as a receiver node.

15. The method of claim 13 , wherein the controller is an impedance controller and the transmitter is an impedance bridge.