Transmitter circuit

A CAN network comprising one or more transmitter circuits, wherein the one or more transmitted circuits each comprise:

• a first bus line terminal and a second bus line terminal for coupling to a bus;
• a controller, wherein the controller is configured to provide a transmission data signal for the bus;
• a voltage setting circuit configured to set a differential driver voltage on the bus;
• an impedance setting circuit that has a first leg and a second leg, wherein each leg comprises an adjustable pull-up resistance and an adjustable pull-down resistance connected in series with each other between the supply terminal and the reference terminal, wherein:
• a first-leg-node between the adjustable pull-up resistance and the adjustable pull-down resistance of the first leg is connected to one of the first bus line terminal or the second bus line terminal;
• and
• a second-leg-node between the adjustable pull-up resistance and the adjustable pull-down resistance of the second leg is connected to another one of the first bus line terminal or the second bus line terminal, and
• wherein the controller is configured to set the adjustable pull-up resistance and the adjustable pull-down resistance of the impedance setting circuit to adjust a driver impedance presented to the bus;
• and
• wherein the controller is configured to detect a transition in the transmission data signal, and in response to a dominant to recessive transition the controller is configured to:
• control the voltage setting circuit such that is sets the differential driver voltage on the bus to a recessive value;
• adjust each of the adjustable pull-up resistances and the adjustable pull-down resistances of the impedance setting circuit with the same target impedance profile such that the transmitter circuit drives the bus with a target driver impedance for an active recessive period of a bit time.

A method of operating a transmitter circuit, wherein the transmitter circuit comprises:

• a first bus line terminal and a second bus line terminal for coupling to a bus;
• an impedance setting circuit that has a first leg and a second leg, wherein each leg comprises an adjustable pull-up resistance and an adjustable pull-down resistance connected in series with each other between the supply terminal and the reference terminal, wherein:
• a first-leg-node between the adjustable pull-up resistance and the adjustable pull-down resistance of the first leg is connected to one of the first bus line terminal or the second bus line terminal;
• and
• a second-leg-node between the adjustable pull-up resistance and the adjustable pull-down resistance of the second leg is connected to another one of the first bus line terminal or the second bus line terminal,
• wherein the method comprises detecting a transition in a transmission data signal, and in response to a dominant to recessive transition in the transmission data signal:
• setting a differential driver voltage on the bus to a recessive value;
• and
• adjusting each of the adjustable pull-up resistances and the adjustable pull-down resistances of the impedance setting circuit with the same target impedance profile such that the transmitter circuit drives the bus with a target driver impedance for an active recessive period, of a bit time.