Transmitting module and method for transmitting differential signals in a serial bus system

A transmitting/receiving device for a subscriber station for a serial bus system, comprising:

• a transmitting module for transmitting differential signals in a serial bus system, including:
• a first, a second, a third, and a fourth transmission stage which are connected in a full bridge, in which the first and fourth transmission stages are connected in series and the third and second transmission stages are connected in series, and
• a current limiting circuit configured to measure and evaluate currents through a first and a second bleeder resistor which are connected to the full bridge,
• wherein the first, second, third, and fourth transmission stages are configured to generate differential bus signals for a bus of the bus system in response to two different values of a digital transmit signal such that the transmitting module generates, in its first operating mode, a first or a second bus state on the bus, and generates, in its second operating mode, a third or fourth bus state, wherein bus signals on the bus form a differential voltage of which a voltage value is different for the first, second, third, and fourth bus states, and
• wherein the current limiting circuit is configured to limit current through the second bleeder resistor based on the evaluation of the currents by the current limiting circuit and according to a value of the digital transmit signal, an operating mode of the transmitting module, and a predefined limit value;
• and
• a receiving module configured to receive signals from the bus.

A subscriber station for a serial bus system, comprising:

• a transmitting/receiving device, including:
• a transmitting module for transmitting differential signals in a serial bus system, including:
• a first, a second, a third, and a fourth transmission stage which are connected in a full bridge, in which the first and fourth transmission stages are connected in series and the third and second transmission stages are connected in series, and
• a current limiting circuit configured to measure and evaluate currents through a first and a second bleeder resistor which are connected to the full bridge,
• wherein the first, second, third, and fourth transmission stages are configured to generate differential bus signals for a bus of the bus system in response to two different values of a digital transmit signal such that the transmitting module generates, in its first operating mode, a first or a second bus state on the bus, and generates, in its second operating mode, a third or fourth bus state, wherein bus signals on the bus form a differential voltage of which a voltage value is different for the first, second, third, and fourth bus states, and
• wherein the current limiting circuit is configured to limit current through the second bleeder resistor based on the evaluation of the currents by the current limiting circuit and according to a value of the digital transmit signal, an operating mode of the transmitting module, and a predefined limit value, and
• a receiving module configured to receive signals from the bus;
• and
• a communication control device configured to control communication in the bus system and to generate a digital transmit signal for controlling the first, second, third, and fourth transmission stages.

A method for transmitting differential signals in a serial bus system, wherein the method is carried out with a transmitting module which has a current limiting circuit and which has a first, second, third, and fourth transmission stage connected in a full bridge, and wherein the method comprises the following steps:

• measuring and evaluating, using the current limiting circuit, currents through a first and a second bleeder resistor which are connected to the full bridge, in which the first and fourth transmission stages are connected in series and the third and second transmission stages are connected in series;
• and
• generating, using the first, second, third, and fourth transmission stages, differential bus signals for a bus of the bus system in response to the two different values of a digital transmit signal such that the transmitting module generates, in its first operating mode, a first or second bus state on the bus, and generates, in its second operating mode, a third or fourth bus state;
• wherein bus signals on the bus form a differential voltage of which a voltage value is different for the first, second, third, and fourth bus states;
• and
• wherein the current limiting circuit limits, in the first operating mode of the transmitting module, current through the second bleeder resistor based on the evaluation of the currents by the current limiting circuit and according to a value of the digital transmit signal, the operating mode of the transmitting module, and a predefined limit value.