Transmitting / receiving device for a bus system and method for reducing oscillations in a bus differential voltage in the event of coupled interference

Description

[0001] The present invention relates to a transmitting / receiving device for a bus system and a method for reducing oscillations of a bus differential voltage in the case of coupled interference, in particular during the transition between different bus states. State of the art

[0002] In a bus system, information or data, contained in bytes or bits, is transmitted as messages over a bus between bus devices. The information is represented by different bit states or voltage states. The different bit states result in different bus states when the message is transmitted over the bus system's bus. Depending on the bus system, different transmission protocols exist for message or data transmission.

[0003] For example, in the CAN bus system, messages are transmitted using the CAN and / or CAN FD protocol, as described in the ISO 11898-1:2015 standard as a CAN protocol specification with CAN FD. The CAN bus system is now widely used for communication between sensors and control units. The CAN bus system is often used in vehicles or automation systems, etc., for communication between individual bus devices.

[0004] CAN and CAN FD use the well-known CSMA / CR method, which, in a first phase for transmitting a message, allows simultaneous access to the bus by subscriber stations of the bus system without destroying a higher-priority message. For this to work, the transmitting / receiving devices, also called transceivers, must be capable of driving the bus with low impedance. This allows a dominant bus state or bit state to be established as one of the two different bus states or bit states. In the recessive state, the other of the two different bus states, the transmitting / receiving devices have a relatively high impedance. The recessive state can be overwritten by a dominant state.

[0005] This is used to negotiate in an arbitration phase which of the participating stations is allowed to send its message on the bus in a subsequent data phase. This ensures exclusive, collision-free access to the bus during the data phase. As a result, data transmission is very robust in both phases. As a result, the frequency of erroneous data transmissions is significantly reduced, thereby increasing the data transmission speed in the bus system.

[0006] To enable data transmission during the data phase at a higher bit rate than with CAN, the CAN FD message format provides an option for switching to a higher bit rate for the data phase. With such technologies, the maximum possible data rate is increased beyond 1 Mbps by using a higher clock rate in the data fields. Such messages are also referred to as CAN FD frames or CAN FD messages. With CAN FD, the payload length is extended from 8 to up to 64 bytes, and the data transmission rates are significantly higher than with CAN.

[0007] The transition from dominant to recessive is subject to oscillation depending on the bus topology, the length of the stubs or drop lines, and the position and number of termination resistors. This is very disadvantageous in system design because, as a result, the bit time must be long enough for the oscillation to be sufficiently damped. If the bit time is not long enough, the transmit / receive device may falsely detect a dominant signal in the recessive state.

[0008] DE 10 2018 202 614 A1 discloses a device that can be connected to the bus system in addition to the subscriber stations. The device has a vibration reduction unit whose duty cycle can be dynamically adjusted to reduce vibrations on the bus by dynamically adjusting the duty cycle.

[0009] The tendency to oscillate can also be amplified by coupled high-frequency interference. High immunity to coupled high-frequency interference is essential for the application of the CAN FD bus in vehicles. Therefore, a predetermined immunity level for a transmitting / receiving device for a bus system must be demonstrated through tests according to the IEC 62228 specification. Disclosure of the invention

[0010] Therefore, the object of the present invention is to provide a transmitting / receiving device for a bus system and a method for reducing oscillations of a bus differential voltage in the presence of coupled interference, which solve the aforementioned problems. In particular, a transmitting / receiving device for a bus system and a method for reducing oscillations of a bus differential voltage in the presence of coupled interference, in particular a tendency to oscillate during the transition from the dominant to the recessive state, are to be provided in a bus system.

[0011] The object is achieved by a transmitting / receiving device for a bus system having the features of claim 1. The transmitting / receiving device comprises a transmitting stage for transmitting a transmitting signal to a first bus wire of a bus of the bus system, in which bus system exclusive, collision-free access of a subscriber station to the bus of the bus system is guaranteed at least temporarily, and for transmitting the transmitting signal to a second bus wire of the bus, and a vibration reduction module for damping an oscillation of a bus signal occurring at connections for the bus wires when the transmitting / receiving device acts as a transmitter of the transmitting signal, wherein the vibration reduction module has a first resistor that can be switched between the first bus wire and a connection for ground, as described in claim 1.In addition, it is possible for the vibration reduction module to have a second resistor that can be connected between the second bus wire and a terminal for a voltage supply of the bus system, as described in claim 2.

[0012] The aforementioned object is also achieved by a transmitting / receiving device for a bus system having the features of claim 2. The transmitting / receiving device comprises a transmitting stage for transmitting a transmitting signal to a first bus wire of a bus of the bus system, in which bus system exclusive, collision-free access of a subscriber station to the bus of the bus system is guaranteed at least temporarily, and for transmitting the transmitting signal to a second bus wire of the bus, and a vibration reduction module for damping a vibration of a bus signal occurring at connections for the bus wires when the transmitting / receiving device acts as a transmitter of the transmitting signal, wherein the vibration reduction module has a resistor that can be switched between the first bus wire and the second bus wire to dampen the vibration, as described in claim 5.

[0013] Each of the previously described transmit / receive devices is designed in such a way that coupled interference can be detected and attenuated at all times, not just during testing procedures. This allows positive counteraction of any coupled interference, such as interference caused by electrostatic discharge (ESD) during operation, ISO pulses, or broadcast interference (BCI), or interference resulting from test procedures such as DPI (Direct Power Injection), etc.

[0014] The described transmit / receive devices enable very good attenuation or reduction of oscillations during the transition from dominant to recessive. This enables reliable reception even at higher bit rates, which are used particularly in the data portion of a message. As a result, the transmission rate or transmission speed of the messages in the bus system increases.

[0015] The described transmit / receive devices can meet the interference immunity requirements of the IEC 62228 specification even at transmission rates of, for example, 2 Mbit or 5 Mbit. At such transmission rates, the pulse edges at the bus state transitions may exhibit much less jitter than with Classical CAN, since the bit time at a transmission rate of 2 Mbit or 5 Mbit is reduced by a factor of 4 to 10 compared to Classical CAN, which has a baud rate of 500 kbit / s.

[0016] In addition, damping and thus reducing the oscillations during the transition between different bit states or voltage states, especially in the CAN bus system from dominant to recessive, allows more freedom in the design of bus topologies and / or terminations and / or stubs and / or the number of nodes or subscriber stations of the bus system.

[0017] Furthermore, the described design of the transmitting / receiving devices achieves a beneficial change in the spectrum of conducted emissions. This is because the radiation of emissions can be reduced in the critical frequency range, which, for example, lies between approximately one and three MHz, which corresponds to the resonant frequency of the common-mode choke and parasitic capacitances. Instead, the described transmitting / receiving devices cause the radiation of emissions to occur in the non-critical frequency range, which in the example above lies at frequencies greater than approximately 10 MHz, and where the choke is effective.

[0018] The transceiver devices are suitable for all communication systems in which a bus state is actively driven, such as CAN bus systems, CAN-HS bus systems, CAN-FD bus systems, etc. With a CAN-HS bus system (HS = high speed), a data transmission rate of up to 500 kbit per second (500 kbps) is possible. With a CAN FD bus system, a data transmission rate of greater than 1 Mbit per second (1 Mbps) is possible.

[0019] Advantageous further embodiments of the respective transmitting / receiving device are described in the dependent claims.

[0020] It is conceivable that the vibration reduction module has a high-frequency detector for detecting high-frequency interference radiation and for determining when the vibration damping of the vibration reduction module should be switched on, so that the first resistor is connected between the first bus wire and the connection for ground and the second resistor is connected between the second bus wire and the connection for the voltage supply of the bus system, wherein the high-frequency detector is designed to instruct the switching on of the vibration reduction module only after a transition from a dominant bus state to a recessive bus state, and wherein the transmitting / receiving device is designed to generate the bus states in such a way that the dominant bus state can overwrite the recessive bus state.

[0021] The transmitting / receiving device may also comprise a timer for switching off the vibration reduction module after a predetermined period of time has elapsed after the vibration damping of the vibration reduction module has been switched on.

[0022] According to one embodiment, the transmitting / receiving device (12A) further comprises a circuit for limiting a negative voltage value of a differential voltage on the bus during a transition of the differential voltage from a dominant bus state to a recessive bus state.

[0023] In a special embodiment, the transmitting / receiving device is designed to send and receive messages according to the CAN FD protocol.

[0024] Perhaps the first and second resistors each have a value of about 150 ohms or the resistor has a value of about 150 ohms.

[0025] Optionally, the receiving stage of the transmitting / receiving device or the vibration reduction module also has a communication phase detection block for detecting different phases of a communication on the bus, wherein the communication phase detection block is designed to switch on the vibration damping of the vibration reduction module depending on the detection result of the communication phase detection block.

[0026] At least one of the previously described transmitting / receiving devices can be part of a bus system comprising a bus and at least two subscriber stations connected to each other via the bus in such a way that they can communicate with each other. At least one of the at least two subscriber stations comprises a previously described transmitting / receiving device.

[0027] Of the at least two subscriber stations, at least one subscriber station may have a communication control device configured to send a signal to the transmitting / receiving device, which signal the transmitting / receiving device uses as a basis for the signal on the bus wires, and to compare the signal with a signal received from the bus by the transmitting / receiving device, and wherein the communication control device is configured to control the vibration reduction module based on the comparison.

[0028] The above-mentioned object is also achieved by a method for reducing oscillations of a bus differential voltage in the case of coupled interference with the features of claim 13.The method is carried out with a transmitting / receiving device for a bus system, in which at least temporarily exclusive, collision-free access of a subscriber station to a bus of the bus system is ensured, the method comprising the steps of: transmitting, with a transmitting stage of the transmitting / receiving device, a transmit signal to a first bus wire of a bus of the bus system, transmitting, with the transmitting stage of the transmitting / receiving device, the transmit signal to a second bus wire of the bus, and damping, with a vibration reduction module, an oscillation of an oscillation of a bus signal occurring at connections for the bus wires when the transmitting / receiving device acts as a transmitter of the transmit signal, wherein a first resistor of the vibration reduction module is connected between the first bus wire and a connection for ground, as described in claim 13.In addition, it is possible for a second resistor of the vibration reduction module to be connected between the second bus wire and a terminal for a voltage supply of the bus system, as described in claim 14.

[0029] The above-mentioned object is also achieved by a method for reducing oscillations of a bus differential voltage in the case of coupled interference with the features of claim 15.The method is carried out with a transmitting / receiving device for a bus system, in which at least temporarily exclusive, collision-free access of a subscriber station to a bus of the bus system is ensured, the method comprising the steps of: transmitting, with a transmitting stage of the transmitting / receiving device, a transmit signal to a first bus wire of a bus of the bus system, transmitting, with the transmitting stage of the transmitting / receiving device, the transmit signal to a second bus wire of the bus, and damping, with a vibration reduction module, an oscillation of an oscillation of a bus signal occurring at connections for the bus wires when the transmitting / receiving device acts as a transmitter of the transmit signal, wherein a resistor of the vibration reduction module is connected between the first bus wire and the second bus wire to dampen the oscillation, as described in claim 15.

[0030] The method offers the same advantages as previously mentioned with regard to the transmitting / receiving device.

[0031] Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention. Drawings

[0032] The invention is described in more detail below with reference to the accompanying drawings and exemplary embodiments. They show: Fig. 1 a simplified block diagram of a bus system according to a first embodiment; Fig. 2 an electrical circuit diagram of a transmitting / receiving device of the bus system according to the first embodiment; Fig. 3 a time course of a differential voltage VDIFF of the bus signals CAN_H and CAN_L at the transmitting / receiving device of Fig. 2 when no high-frequency disturbance occurs, whereby the vibration reduction module is only switched on before the second change from the recessive bus state to the dominant bus state; Fig. 4 a time course of a differential voltage VDIFF of the bus signals CAN_H and CAN_L at the transmitting / receiving device of Fig. 2 when a high-frequency disturbance occurs, whereby the vibration reduction module is only switched on before the second change from the recessive bus state to the dominant bus state; Fig. 5 an electrical circuit diagram of a transmitting / receiving device of a bus system according to a second embodiment; Fig. 6 an electrical circuit diagram of a transmitting / receiving device of a bus system according to a third embodiment; and Fig. 7 a diagram illustrating the structure of a message sent by a subscriber station of the bus system according to the third embodiment.

[0033] In the figures, identical or functionally equivalent elements are provided with the same reference numerals unless otherwise stated. Description of the embodiments

[0034] Fig. 1 shows a bus system 1, which can, for example, at least in sections, be a CAN bus system, a CAN-FD bus system, etc. The bus system 1 can be used in a vehicle, in particular a motor vehicle, an aircraft, etc., or in a hospital, etc.

[0035] In Fig. 1 The bus system 1 has a plurality of subscriber stations 10, 20, 30, each connected to a bus 40 with a first bus wire 41 and a second bus wire 42. The bus wires 41, 42 can also be called CAN_H and CAN_L and are used for electrical signal transmission after coupling in the dominant levels or generating recessive levels for a signal in the transmit state. Messages 45, 46, 47 can be transmitted in the form of signals between the individual subscriber stations 10, 20, 30 via the bus 40. The subscriber stations 10, 20, 30 are, for example, control units or display devices of a motor vehicle.

[0036] As in Fig. 1 As shown, the subscriber stations 10, 30 each have a communication control device 11 and a transmitting / receiving device 12. The transmitting / receiving devices 12 each comprise a vibration reduction module 15. The subscriber station 20, on the other hand, has a communication control device 11 and a transmitting / receiving device 13. The transmitting / receiving devices 12 of the subscriber stations 10, 30 and the transmitting / receiving device 13 of the subscriber station 20 are each directly connected to the bus 40, even if this is not the case in Fig. 1 is not shown.

[0037] The communication control device 11 is used to control communication between the respective subscriber station 10, 20, 30 via the bus 40 and another subscriber station of the subscriber stations 10, 20, 30 connected to the bus 40. The transmitting / receiving device 12 is used to transmit the messages 45, 47 in the form of signals and, in doing so, uses the vibration reduction module 15, as described in more detail later. The communication control device 11 can be designed, in particular, as a conventional CAN FD controller and / or CAN controller. The transmitting / receiving device 13 can be designed, in particular, as a conventional CAN transceiver and / or CAN FD transceiver. The transmitting / receiving device 13 can be designed, in particular, as a conventional CAN transceiver.

[0038] Fig. 2 shows the basic structure of the transmitting / receiving device 12 with the vibration reduction module 15. The transmitting / receiving device 12 is connected to the bus 40 via terminals 41A, 42A, more precisely to its first bus wire 41 for CAN_H and its second bus wire 42 for CAN_L. The voltage supply, in particular CAN supply, for the first and second bus wires 41, 42 is via a terminal 43. The connection to ground or CAN_GND is realized via a terminal 44. A common-mode choke 48, also called a common-mode choke, is connected between the terminals 41A, 42A and the first and second bus wires 41, 42. The common-mode choke 48 causes In particular, a reduction in the radiation of high-frequency energy and interference with radio reception by the bus 40. The first and second bus wires 41, 42 are terminated with a terminating resistor 49.

[0039] The first and second bus wires 41, 42 are connected in the transmitting / receiving device 12 to a transmitting stage 121, which is also referred to as a transmitter. Furthermore, the first and second bus wires 41, 42 in the transmitting / receiving device 12 are also connected to a receiving stage 122, which is also referred to as a receiver. For this purpose, the receiving stage 122, as is conventional, has a receiving comparator 1221, which is connected to the bus 40, although this is not the case in Fig. 2 not shown for simplification.

[0040] The precise connection for driving a digital transmission signal TxD from the communication control device 11 via a terminal 111 is carried out as is conventional. Furthermore, the connection for driving a reception signal RxD via a terminal 112 to the communication control device 11 is carried out as is conventional. Therefore, this connection is Fig. 2 Not shown for simplicity. The digital receive signal RxD was generated by the receive stage 122 from the signal received by the bus wires 41, 42.

[0041] According to Fig. 2 The transmitting stage 121 has a conventional driver 1211 for the signals for the first and second bus wires 41, 42. Furthermore, the vibration reduction module 15 is built into or connected to the transmitting stage 121. The functionality of the vibration reduction module 15 is only active in the transmitting / receiving device 12 when the transmitting / receiving device 12 itself is transmitting or acting as a transmitter. To determine whether the transmitting / receiving device 12 is acting as a transmitter, the evaluation of the transmitted signal TxD can be performed, in particular.

[0042] The vibration reduction module 15 includes a terminal 150 for switching the vibration reduction module 15 on or off. The vibration reduction module 15 also includes a first resistor 151, a first diode 152, which may be a first drain-bulk diode of a MOSFET of the semiconductor substrate of the transmission stage 121, and a first transistor 153 as a switch for the first bus wire 41. Furthermore, the module 15 includes a second resistor 155, a second diode 156, which may be a second drain-bulk diode of a MOSFET of the semiconductor substrate of the transmission stage 121, and a second transistor 157 as a switch for the second bus wire 42. Furthermore, the vibration reduction module 15 includes an inverter 158 and a high-frequency detector 159, the output of which is connected to the terminal 150. The input of the high frequency detector 159 is connected to the bus 40, although this is Fig. 2 Not shown to simplify the drawing. The output of the high-frequency detector 159 is connected to the control terminal of transistor 153.

[0043] More specifically, the vibration reduction module 15 for the first bus wire 41 includes a first resistor 151, a first diode 152, and a first transistor 153 connected in series in the order mentioned. Furthermore, the vibration reduction module 15 for the second bus wire 42 includes a second resistor 155, a second diode 156, and a second transistor 157 connected in series in the order mentioned.

[0044] The first resistor 151 is connected at one end to the first bus wire 41, i.e., to CAN_H in the present embodiment. One end of the transistor 153 is connected to ground or CAN_GND via terminal 44. The transistor 153 can be implemented, for example, as a metal-insulator field-effect transistor. In particular, the transistor 153 is implemented as a metal-oxide field-effect transistor (MOSFET) or as an insulated-gate field-effect transistor, also referred to as an IGFET.

[0045] The second resistor 155 is connected at one end to the second bus wire 42, i.e., to CAN_L in the present embodiment. One end of the transistor 157 is connected via terminal 43 to the voltage supply for the bus 40 or for CAN. The transistor 157 can be implemented, for example, as a metal-insulator field-effect transistor. In particular, the transistor 157 is implemented as a metal-oxide field-effect transistor (MOSFET) or as an insulated-gate field-effect transistor (IGFET).

[0046] Thus, a resistor 151 is connected from CAN_H or the first bus wire 41 to ground and a resistor 155 is connected from CAN_L or the second bus wire 42 to the voltage supply, which is usually 5V for CAN.

[0047] The resistors 151, 155 with their resistance value R cause a damping of the oscillation tendency of the signals, as described below with reference to Fig. 3 und Fig. 4 explained in more detail.

[0048] During operation of the bus system 1, the high frequency detector 159 detects Fig. 2 high-frequency interference on the bus 40. High-frequency interference is understood in this context as signals with frequencies whose period duration is less than a bit time duration T B_402 or T B_401 according to Fig. 3 or Fig. 4 or in a range of approximately 5 MHz to approximately 50 MHz. The high-frequency detector 159 may comprise at least one filter for this purpose, in particular a high-pass and / or a low-pass and / or a band-pass filter. The high-frequency detector 159 comprises a timing element 1591, which enables the oscillation reduction module 15 to be switched on via the terminal 150 and thus attenuates the bus 40 only for a short period of time TD after the dominant-recessive edge, as shown in Fig. 3 or Fig. 4 shown. The time period TD is no longer than 100 ns. This ensures that the other subscriber stations 20, 30 can continue to communicate.

[0049] The vibration reduction module 15 has the advantage, due to the previously described structure, that the module 15 can not only reduce the bus voltage to 0V, but that the bus voltage even becomes negative due to the module 15, as can be seen from Fig. 3 und Fig. 4 This further increases the interference immunity of the transmitting / receiving device 12 and thus provides an additional advantage.

[0050] Fig. 3 shows a time profile of a differential voltage VDIFF = CAN_H - CAN_L between the bus wires 41, 42 or 41A, 41B in the transmitting / receiving device 12 according to the present embodiment. The signal from Fig. 3 is set as a result of a transmission signal TxD, which was sent from one of the subscriber stations 10, 20, 30 on the bus 40. In the example of Fig. 3 There is no high-frequency interference. The signal from Fig. 3 occurs when the vibration reduction module 15 is initially switched off and is only switched on from a time t1.

[0051] At the differential voltage VDIFF of Fig. 3 Over time t, two state changes take place one after the other, from a first bus state 401 to a second bus state 402 and then back to the first bus state 401. In the example of Fig. 3 the second bus state 402 only one bit of the transmit signal TxD, whereby in the signal from Fig. 3 sets a bit time duration T B_402 for the second bus state 402. The first bus state 401 can also be referred to as a recessive state or high level of the CAN_H, CAN_L signals. The second bus state 402 can also be referred to as a dominant state or low level of the CAN_H, CAN_L signals.

[0052] The bit time duration T B_402 for a dominant bus state 402 should ideally be equal to a bit time duration T B_401 for a recessive bus state 401. If the differential voltage VDIFF of Fig. 3 at a sampling point of the bus state below a reception threshold T_s1 of the reception stage 122, the reception stage 122 recognizes the bus state as a recessive bus state 401. In the example of Fig. 3 the reception threshold T_s1 is 0.3 V. If the differential voltage VDIFF of Fig. 3 If the sampling point of the bus state is above a reception threshold T_s2 of the reception stage 122, the reception stage 122 recognizes the bus state as the dominant bus state 402.

[0053] According to Fig. 3 has the differential voltage VDIFF on the left side of Fig. 3 , i.e. before time t1, during the transition from state 402 to state 401 there is a significantly larger overshoot than on the right side of Fig. 3 , i.e., after time t1. The oscillation reduction module 15, which was switched on at time T1, thus significantly dampens the overshoot during the transition from state 402 to state 401. Resistors 151, 155 of the oscillation reduction module 15 are dimensioned such that a negative differential voltage VDIFF of up to -0.5 V occurs during the transition from state 402 to state 401. For this purpose, resistors 151, 155 have a value of approximately 150 ohms. Of course, other values for resistors 151, 155 can be selected.

[0054] Fig. 4 In comparison, shows a time profile of a differential voltage VDIFF = CAN_H - CAN_L between the bus wires 41, 42 in the transmitting / receiving device 12 according to the present embodiment when high-frequency interference radiation H_S is present. The signal from Fig. 4 occurs when the vibration reduction module 15 is initially switched off and is only switched on from time t1, as in the example of Fig. 3 .

[0055] As in the left part of Fig. 4 As shown, the differential voltage VDIFF is now Fig. 4 due to the interference radiation H_S directly after the transition from state 402 to state 401 for a significantly longer period of time above the reception threshold T_s1 of the reception stage 122. Thus, the differential voltage VDIFF on the left side of Fig. 4 , i.e. before the time t1 at which the vibration reduction module 15 is switched on, after the transition from state 402 to state 401 a significantly larger overshoot than on the right side of Fig. 4 , i.e. after time t1.

[0056] The vibration reduction module 15 thus causes a significant damping of the overshoot during the transition from state 402 to state 401, even in the case of interference radiation H_S. By dimensioning the resistors 151, 155 of the vibration reduction module 15 as in the example of Fig. 3 , a negative differential voltage VDIFF of up to approximately -0.6 V occurs during the transition from state 402 to state 401.

[0057] As a result, the vibration reduction module 15 can significantly increase the interference immunity of the transmitting / receiving device 12 according to the present embodiment. Thus, in the case of superimposed high-frequency interference, the most common dominant reception threshold T_s2 of 0.9 V cannot be erroneously exceeded. This also applies if the threshold voltage or reception threshold T_s1 of the reception stage 122 for evaluating a bus state as a recessive bus state 401 is set to the usual value of T_s1 = 0.5 V or even to a value of T_s1 = 0.3 V as in Fig. 3 und Fig. 4 illustrated. In such cases, the receiving stage 122 no longer overlooks any state changes from state 402 to state 401 or from recessive to dominant, even in the case of a state change from state 402 to state 401 or from dominant to recessive.

[0058] Thus, sampling the differential voltage VDIFF to generate the received signal RxD at the currently common sampling point AP = x * T B_402 can reliably lead to the desired result. This applies even if the length of the bit time T B_402 of the state 402 or a dominant bit should be somewhat longer compared to a conventional transmitting / receiving device or the transmitting / receiving device 13 of the subscriber station 20, as can be seen from Fig. 3 und Fig. 4 visible. To determine the sampling point, x is approximately equal to 0.75. Alternatively, the transmitting / receiving device can determine the value for x during the arbitration phase (lower bit rate) of bus system 1 in order to adapt the sampling point of the bits for the following data phase (higher bit rate = faster data transmission) to the currently applicable operating conditions.

[0059] Thus, the transmitting / receiving device 12 according to the present embodiment has a lower tendency to oscillate than a conventional transmitting / receiving device or the transmitting / receiving device 13, not only in the case of high-frequency interference radiation H_S.

[0060] Therefore, a method for reducing the tendency to oscillate during the transition between different bus states is implemented with the transmitting / receiving device 12. The oscillation resulting from a transition between different bus states is significantly dampened and thus reduced by the oscillation reduction module 15.

[0061] In the described embodiment, only the subscriber stations 10, 30 have the functionality of the transmitting / receiving device 12. The subscriber stations 10, 30 are preferably subscriber stations or nodes with a high oscillation tendency and / or subscriber stations or nodes requiring high immunity to high-frequency radiation H_S. The high oscillation tendency of the subscriber stations 10, 30 can result in particular from their position in the bus system 1, the position of the termination resistors 49, the stub length or drop line length to the subscriber stations 10, 30, etc.

[0062] Furthermore, the described transmitting / receiving device 12 also enables the use of bulk silicon technologies. With such technologies, the design of the transmitting / receiving device 12 allows the dominant-to-recessive edge of the differential signal VDIFF to be kept temporally stable, even at high interference levels of radiation H_S, which occur when ESD structures such as the choke 48 intervene. The transmitting / receiving device 12 prevents the current draining of the reverse polarity protection diodes in the CAN FD transmitting stage 121 from causing abrupt current chopping, which then excites the choke 48 with its parasitic capacitances to oscillate. These oscillations would lead to high jitter of the dominant-to-recessive edge at the output of the receiving stage 122. Under certain circumstances, the receiving stage 122 would even detect a short dominant peak or spike, which would also lead to an error and thus to lower interference immunity.

[0063] According to a modification of the first embodiment, the subscriber station 20 also has a transmitting / receiving device 12 instead of a transmitting / receiving device 13. In this case, the previously described functionality of the transmitting / receiving device 12 is active for all subscriber stations 10, 20, 30 of the bus system, in particular as required.

[0064] Fig. 5 shows the basic structure of a transmitting / receiving device 12A, which has a transmitting stage 121A and a vibration reduction module 15A according to a second embodiment. Except for the differences described below, the bus system 1 and the transmitting / receiving device 12A are constructed in the same manner as previously described according to the preceding embodiment or its modifications for the bus system 1 and the transmitting / receiving device 12.

[0065] The oscillation reduction module 15A additionally has a circuit block 160 that implements a switchable voltage limit of the differential voltage VDIFF during the transition from state 402 to state 401. In particular, the switchable voltage limit of the differential voltage VDIFF is a negative differential voltage VDIFF = -0.6 V.

[0066] In this variant, resistors 151, 155 are less than 150 ohms, for example, 50 ohms. The differential voltage VDIFF on bus 40 is limited to -0.6V by means of a switchable diode 161 during the attenuation process during the transition from state 402 to state 401. Diode 161 is switchable by means of a switch 162, which can be implemented as a transistor. The transistor or switch 162 can be implemented like one of the transistors previously mentioned with reference to the first embodiment. Switch 162 is connected in series with diode 161. In addition, a reverse polarity protection diode 163 and a switch 164 are provided towards terminal 43 for the voltage supply. Switch 164 can be implemented as a transistor in the manner previously mentioned with reference to the first embodiment. A resistor 165 is connected between the gate terminal and the source terminal of the switch 162.

[0067] To control switch 162, PMOS switch 164 or PMOS transistor 164 opens, allowing electrical current to flow through diode 163. The electrical current from diode 163 generates a positive gate-source voltage across NMOS switch 162 via gate-source resistor 165, which opens NMOS switch 162 and clamps VDIFF = CAN_H - CAN_L to the forward voltage of diode 161. The forward voltage of diode 161 is approximately 0.6 V. The control current from transistor 164 then flows via resistor 151, reverse polarity protection diode 152, and NMOS transistor 153 to CAN_GND. The control current for switch 164 is set such that the common-mode level of 2.5 V is set on bus 40 via the series circuit of 151, 152, and 153. The gate-source resistor 165 is selected such that the maximum possible gate-source voltage is formed across switch 162.The resistance of resistor 155 is thus chosen to be slightly larger than the resistance of resistor 151. The electric current through resistor 155 will be smaller than the current through resistor 151 by exactly the amount of the control current through 164, 163, and resistor 165 via the gate and source terminals of switch 162.

[0068] The circuit 160 has the advantage that for the signals from Fig. 3 und Fig. 4 The recessive bus state 401 is reached even faster. Furthermore, the described transmit / receive device 12B also enables the use of bulk silicon technologies. However, the disadvantage of circuit 160 is that switch 162 must be controlled and the reverse polarity protection diode 163 must be taken into account.

[0069] Fig. 6 shows the basic structure of a transmitting / receiving device 12B, which has a transmitting stage 121B and a vibration reduction module 15B according to a second exemplary embodiment. Except for the differences described below, the bus system 1 and the transmitting / receiving device 12B are constructed in the same manner as previously described according to the preceding exemplary embodiment or its modifications for the bus system 1 and the transmitting / receiving device 12.

[0070] Instead of two resistors 151, 155 and their interconnection, the vibration reduction module 15B has only one resistor 151, which can be switched with a switch 151B. The resistor 151 is connected in series with the switch 151B. The series circuit of resistor 151 and switch 151B is connected between the bus wires 41, 42. This also allows damping of the vibrations during a transition from state 402 to state 401.

[0071] The vibration reduction module 15B is less suitable for a transceiver 12B that uses bulk silicon technologies. This is because a parasitic diode always forms in the substrate of the transceiver 12B, which in turn leads to rectification effects in the presence of high-frequency interference radiation.

[0072] Optionally, the high-frequency detector 159 has a communication phase detection block 1592, illustrated only schematically, which is connected upstream of the timing element 1591. Block 1592 allows the switch 151B to be actuated depending on the different phases of a communication on the bus 40. The communication phase detection block 1592 can only enable the timing element 1591 or switch the damping of the vibration reduction module 15B on or off when the data phase of a message 45, 46, 47 is present.

[0073] The different phases of a communication can be detected and recognized or distinguished by the communication phase detection block 1592, as shown by Fig. 7 described in more detail. The communication phase detection block 1592 may instead be part of the receiving stage 122 or part of the vibration reduction module 15B.

[0074] The communication phase detection block 1592 may, for example, comprise a differential amplifier whose inputs are connected in parallel with the inputs of the receive comparator 1221 of the receive stage 122. At least one output of the detection block 1592 can be used to control the switch 151B.

[0075] Fig. 7 shows, in its upper part, based on message 45, a CAN frame as sent by the transmitting / receiving device 12, 12A, 12B or the transmitting / receiving device 13, and in its lower part, a CAN-FD frame as can be sent by the transmitting / receiving device 12, 12A, 12B. For CAN communication on the bus 40, the CAN frame and the CAN-FD frame are fundamentally divided into two different communication phases, namely the arbitration phases 451, 453 and a data area 452, which is also called a data field in CAN-HS and a data phase in CAN-FD. The data area 452 is terminated at its end with at least one end bit 454, which is also called an EOF bit, where EOF stands for end of frame or end of message. For CAN or CAN FD, the EOF is a bit sequence of 11 recessive bits, i.e. bits with the second bus state 402.

[0076] In CAN-FD, compared to classic CAN, the bit rate for the following data phase is increased to, for example, 2, 4, or 8 Mbit per second (Mbps) at the end of arbitration phase 451. This means that in CAN-FD, the bit rate in arbitration phases 451 and 453 is lower than the bit rate in data area 452. In CAN-FD, data area 452 is significantly shorter than the data area 452 of the CAN frame.

[0077] The arbitration phases 451, 453 are an important part of a CAN frame and a CAN FD frame or the messages 45, 46, 47, which are Fig. 1are shown. This determines which node or subscriber station 10, 20, 30 of bus system 1 carries the most important message 45, 46, 47. The subscriber station 10, 20, 30 with the most important message 45, 46, 47 wins the arbitration and is therefore permitted to transmit the message after the arbitration phase has ended. All other subscriber stations are then listeners, i.e., only receivers, when transmitting this most important message.

[0078] The communication phase detection block 1592 can detect the arbitration phases 451, 453, the data area 452, and the end of the data area 453, i.e., the end of the data area 453, i.e., the end of the data area (EOF) 454. This allows the functionality of the oscillation reduction module 15B to apply, as desired, either to all communication phases 451 to 453 or phases / areas of a message 45, or only when arbitration is completed, i.e., to the data area 452. The latter is useful if otherwise too many subscriber stations 10, 20, 30 could simultaneously activate the function of the transmit / receive device 12B during arbitration, thus excessively reducing the effective bus resistance.

[0079] According to a fourth embodiment, it is possible for the communication control device 11 of one of the transmitting / receiving devices 12, 12A, 12B of the previous embodiment to send a control signal to activate the attenuation of the modules 15, 15A, 15B. In this case, the communication control device 11 would have to have an additional connection for a control signal in addition to the connections 111, 112 for the TxD, RxD signals.

[0080] To generate the control signal, the communication control device 11 can monitor the bus traffic on the bus wires 41, 42 by comparing the transmit signal TxD sent at terminal 111 and the receive signal RxD received at terminal 112, which is buffered if necessary. If deviations occur between the two signals TxD and RxD in the recessive bus state, i.e., the first bus state 401, such as state changes in the receive signal RxD that were not included in the transmit signal TxD, conclusions can be drawn about the network or bus 40 and the signal integrity.

[0081] Furthermore, the communication control device 11 can use information such as bit rate and propagation delay for both switching processes, i.e., a state change from the first bus state 401 to the second bus state 402, to generate the control signal. The information can be stored in a block (not shown), in particular, memory.

[0082] In this way, the control of the ringing suppression is not controlled by the transmitting / receiving device 12, 12A, 12B connected to the device 11, but by the communication control device 11. The communication control device 11 can adapt the ringing reduction module 15, 15A, 15B to the specific characteristics of the subscriber station 10 and the network or bus 40. In other words, the communication control device 11 can adjust the ringing reduction module 15, 15A, 15B to be node- and network-sensitive. The communication control device 11 thus provides a learning function for the subscriber station 10.

[0083] This also allows a significant reduction in the tendency to oscillate during the state change from the second bus state 402 to the first bus state 401. Furthermore, this can result in a significant gain for the bus system 1 as a whole.

[0084] All previously described configurations of the vibration reduction modules 15, 15A, 15B, the transmitting / receiving devices 12, 12A, 12B, the subscriber stations 10, 20, 30, the bus system 1, and the method implemented therein according to the exemplary embodiments and their modifications can be used individually or in all possible combinations. In addition, the following modifications are particularly conceivable.

[0085] In particular, the communication phase detection block 1592 and the associated functionality of the vibration reduction module 15B can be used in any of the embodiments and their modifications.

[0086] The previously described bus system 1 according to the exemplary embodiments and / or modifications thereof is described with reference to a bus system based on the CAN protocol. However, the bus system 1 according to the exemplary embodiments and / or modifications thereof can also be a different type of communications network. It is advantageous, but not a mandatory requirement, that in the bus system 1, exclusive, collision-free access of a subscriber station 10, 20, 30 to the bus line 40 or a common channel of the bus line 40 is guaranteed, at least for certain periods of time.

[0087] The bus system 1 according to the exemplary embodiments and / or modifications thereof is, in particular, a CAN network, a CAN-HS network, a CAN FD network, or a FlexRay network. However, the bus system 1 can also be another serial communication network.

[0088] In particular, the vibration reduction module 15, 15A, 15B can be used with LVDS (Low Voltage Differential Signaling), an interface standard for high-speed data transmission in which a transmitter and a receiver are connected via a data transmission link. LVDS is standardized according to ANSI / TIA / EIA-644-1995.

[0089] The number and arrangement of subscriber stations 10, 20, 30 in the bus system 1 according to the exemplary embodiments and / or their modifications is arbitrary. In particular, only subscriber stations 10 or subscriber stations 30 can be present in the bus systems 1 of the exemplary embodiments and / or their modifications.

[0090] The functionality of the previously described embodiments and / or their modifications can each be implemented in a transceiver or a transmitting / receiving device 12, 12A, 112B or transceiver or a CAN transceiver or a transceiver chipset or a CAN transceiver chipset, etc. Additionally or alternatively, it can be integrated into existing products. In particular, it is possible for the functionality under consideration to be implemented either in the transceiver as a separate electronic component (chip) or embedded in an integrated overall solution in which only one electronic component (chip) is present.

Claims

1. Transmitting / receiving device (12; 12A; 12B) for a bus system (1), having a connection (44) for connection to earth, a connection (43) for connection to a voltage supply of the bus system (1), a connection (41A) for connection to a first bus wire (41), a connection (42A) for connection to a second bus wire (42), a transmission stage (121; 121A; 121B) for transmitting a transmission signal (TxD) to the connection (41A) for the first bus wire (41) of a bus (40) of the bus system (1), in which bus system (1) exclusive collision-free access of a subscriber station (10, 20, 30) to the bus (40) of the bus system (1) is at least temporarily ensured, and for transmitting the transmission signal (TxD) to the connection (42A) for the second bus wire (42) of the bus (40), and an oscillation reduction module (15; 15A; 15B) for damping an oscillation of a bus signal (VDIFF) arising at the connections (41A, 42A) for the bus wires (41, 42) when the transmitting / receiving device (12; B) acts as transmitter of the transmission signal (TxD), wherein the oscillation reduction module (15; 15A; 15B) has a first resistor (151) which can be switched between the connection (41A) for the first bus wire (41) and the connection (44) for earth using a first switch (153; 151B) connected in series with the first resistor (151).

2. Transmitting / receiving device (12; 12A) according to Claim 1, wherein the first switch (153) is a first transistor and the first resistor (151) can be switched between the connection (41A) for the first bus wire (41) and the connection (44) for earth using the series-connected first switch (153) as a switch for the first bus wire (41), and wherein the oscillation reduction module ((15; 15A) has a second resistor (155) which can be switched between the connection (42A) for the second bus wire (42) and the connection (44) for the voltage supply of the bus system (1) using a second transistor (153) connected in series with the second resistor (155) as a switch (157) for the second bus wire (42).

3. Transmitting / receiving device (12; 12A; 12B) according to Claim 2, wherein the first and second resistors (151, 155) each have a value of approximately 150 ohms.

4. Transmitting / receiving device (12A) according to any one of the preceding claims, furthermore having a circuit (160) for limiting a negative voltage value of a differential voltage (VDIFF) on the bus (40) in the event of a transition of the differential voltage (VDIFF) from a dominant bus state (402) to a recessive bus state (401).

5. Transmitting / receiving device (12B) according to Claim 1, wherein the first resistor (151) can be switched between the first bus wire (41) and the second bus wire (42) using the series-connected first switch (151B) for damping the oscillation.

6. Transmitting / receiving device (12B) according to Claim 5, wherein the first resistor (151) is connected to the connection (41A) for connection to the first bus wire (41), and wherein the first switch (151B) is connected to the connection (42A) for connection to the second bus wire (42), and wherein the first resistor (151) in particular has a value of approximately 150 ohms.

7. Transmitting / receiving device (12; 12A; 12B) according to any one of the preceding claims, wherein the oscillation reduction module (15; 15A; 15B) has a high-frequency detector (159) for detecting high-frequency interference radiation (H_S) and for ascertaining when the oscillation damping of the oscillation reduction module (15; 15A; 15B) is to be switched on, so that the first resistor (151) is switched between the first bus wire (41) and the connection (44) for earth, and the second resistor (155) is switched between the second bus wire (42) and the connection (44) for the voltage supply of the bus system (1), wherein the high-frequency detector (159) is configured to instruct the oscillation reduction module (15; 15A; 15B) to be switched on only after a transition from a dominant bus state (402) to a recessive bus state (401), and wherein the transmitting / receiving device (12; 12A; 12B) is configured to generate the bus states (401, 402) in such a way that the dominant bus state (402) is able to overwrite the recessive bus state (401).

8. Transmitting / receiving device (12; 12A; 12B) according to any one of the preceding claims, further having a timer (1592) for switching off the oscillation reduction module (15; 15A; 15B) after expiration of a predetermined time period (TD) after the oscillation damping of the oscillation reduction module (15; 15A; 15B) is switched on.

9. Transmitting / receiving device (12; 12A; 12B) according to any one of the preceding claims, wherein the transmitting / receiving device (12; 12A; 12B) is configured to transmit and receive messages (45, 47) according to the CAN FD protocol.

10. Transmitting / receiving device (12; 12A; 12B) according to any one of the preceding claims, wherein the receiving stage (122) of the transmitting / receiving device (12; 12A; 12B) or the oscillation reduction module (15B) also has a communication phase detection block (1592) for detecting different phases of a communication on the bus (40), and wherein the communication phase detection block (1592) is configured to switch on the oscillation damping of the oscillation reduction module (15; 15A; 15B) as a function of the detection result of the communication phase detection block (1592).

11. Bus system (1) having a bus (40), and at least two subscriber stations (10; 20; 30) which are connected to one another via the bus (40) in such a way that they can communicate with one another, wherein at least one of the at least two subscriber stations (10; 20; 30) has a transmitting / receiving device (12; 12A; 12B) according to any one of the preceding claims.

12. Bus system (1) according to Claim 11, wherein one of the at least two subscriber stations (10; 20; 30) has a communication control device (11) which is configured to transmit a signal (TxD) to the transmitting / receiving device (12; 12A; 12B), which signal uses the transmitting / receiving device (12; 12A; 12B) as a basis for the signal (VDIFF) on the bus wires (41, 42), and to compare the signal (TxD) with a signal (RxD) received from the bus (40) by the transmitting / receiving device (12; 12A; 12B), and wherein the communication control device (110) is configured to actuate the oscillation reduction module (15; 15A; 15B) on the basis of the comparison.

13. Method for reducing oscillations of a bus differential voltage in the case of coupled-in interference, wherein the method is executed using a transmitting / receiving device (12; 12A; 12B)) for a bus system (1), in which exclusive, collision-free access of a subscriber station (10, 20, 30) to a bus (40) of the bus system (1) is at least temporarily ensured, wherein the transmitting / receiving device (12; 12A; 12B)) has a connection (44) connected to earth, a connection (43) connected to a voltage supply of the bus system (1), a connection (41A) connected to a first bus wire (41), and a connection (42A) connected to a second bus wire (42), a transmission stage (121; 121A; 121B)) and an oscillation reduction module (15; 15A; 15B)), and wherein the method comprises the steps of transmitting, using the transmission stage (121; 121A), a transmission signal (TxD) to the connection (41A) for the first bus wire (41) of a bus (40) of the bus system (1), transmitting, using the transmission stage (121; 121A), the transmission signal (TxD) to the connection (42A) for the second bus wire (42) of the bus (40), and damping, using an oscillation reduction module (15; 15A), an oscillation of a bus signal (VDIFF) arising at the connections (41A, 42A) for the bus wires (41, 42) when the transmitting / receiving device (12; 12A; 12B)) acts as transmitter of the transmission signal (TxD), wherein, to damp the oscillation, the oscillation reduction module (15; 15A; 15B)) uses a first switch (153; 151B) connected in series with the first resistor (151) to switch a first resistor (151) of the oscillation reduction module (15; 15A; 15B)) between the connection (41A) to which the first bus wire (41) is connected and the connection (44) connected to earth.

14. Method according to Claim 13, wherein the first switch (153) is a first transistor and, in the damping step, the first resistor (151) is switched between the connection (41A) for the first bus wire (41) and the connection (44) for earth using the series-connected first switch (153) as a switch for the first bus wire (41), and wherein, to damp the oscillation, the oscillation reduction module (15; 15A) uses a second transistor (153) connected in series with the second resistor (155) as a switch (157) for the second bus wire (42) to switch a second resistor (155) of the oscillation reduction module (15; 15A) between the connection (42A) to which the second bus wire (42) is connected and the connection (43) to which the voltage supply of the bus system (1) is connected.

15. Method according to Claim 13, wherein the method furthermore comprises the following step damping, using the oscillation reduction module (15B), an oscillation of a bus signal (VDIFF) arising at connections (41A, 42A) for the bus wires (41, 42) when the transmitting / receiving device (12b) acts as transmitter of the transmission signal (TxD), wherein, to damp the oscillation, the oscillation reduction module (15B) uses the series-connected first switch (151B) to switch the first resistor (151) of the oscillation reduction module (15B) between the connection (41A) connected to the first bus wire (41) and the connection (42A) connected to the second bus wire (42).