Controller Area Network Controllers and Transceivers

Abstract

A controller area network (CAN) transceiver comprises: two terminals for coupling to a CAN bus; a transmitter arrangement configured to transmit signaling on the bus based on transmission data, the transmitter arrangement configured to drive the bus to a dominant state or a recessive state based on a transmission signal; an impedance control device; a signaling detector configured to determine a length of time that the transmission data includes a logic zero before transitioning to a logic one state, and: based on the length of time being longer than a predetermined threshold, providing control of output impedance by the impedance control device according to a first scheme; and based on the length of time being shorter than the predetermined threshold, providing one of the following operations: controlling the output impedance according to a second scheme; and not controlling the output impedance by the impedance control device.

Description

Technical Field

[0001] The present disclosure relates to a controller area network (CAN) node transceiver. The present disclosure also relates to one of the following: a CAN node comprising a CAN controller and a CAN transceiver, and a method of operating the controller or transceiver. Background Art

[0002] A CAN network uses a bus to enable communication between nodes. Nodes connected to the bus can transmit data to and receive data from other nodes connected to the bus. A CAN network implements the CAN protocol, which defines how communication between nodes is done. Summary of the Invention

[0003] According to a first aspect of the present disclosure, a controller area network (CAN) transceiver is provided, comprising:

[0004] two bus terminals, the two bus terminals being used to couple the transceiver to a CAN bus;

[0005] a transmitter arrangement configured to transmit signaling on the CAN bus via the bus terminals based on transmission data received at a transmission input, the transmission input comprising a terminal for coupling to a CAN controller, the transmitter arrangement comprising at least one transmitter configured to drive the bus into a dominant state or a recessive state based on a transmission signal, and comprising impedance control means connected to the two bus terminals;

[0006] a signaling detector configured to detect signaling received at the transmission input with the transmission data from the controller, the signaling detector configured to determine a length of time the transmission data includes the logic zero state before the transmission data transitions from the logic zero state to the logic one state, and:

[0007] Based on the length of time being longer than a predetermined threshold, the impedance control device provides control of the output impedance according to a first scheme, including controlling the output impedance within a predefined range of impedance values in the dominant state when a differential drive voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, and then increasing the output impedance for a first predetermined time duration; and

[0008] Based on the time length being shorter than the predetermined threshold, one of the following operations is provided: controlling the output impedance according to a second scheme different from the first scheme; and the impedance control device not controlling the output impedance.

[0009] In one or more embodiments, the signaling detector includes a time filter configured to provide a switching signal based on whether the time length is longer or shorter than the predetermined threshold, wherein the signaling detector further includes a multiplexer configured to receive the switching signal and switch between the following states based on the switching signal:

[0010] a first state in which the multiplexer is configured to connect a first control block to provide signaling to the impedance control device to provide the first scheme; and

[0011] A second state, in which the multiplexer is configured to: connect a second control block to provide signaling to the impedance control device to provide the second scheme; or disconnect the first control block from the impedance control device.

[0012] In one or more embodiments, based on the length of time being shorter than the predetermined threshold, the signaling detector is configured to provide control of the output impedance according to the second scheme.

[0013] In one or more embodiments, the transmitter arrangement comprises a first transmitter and a second transmitter, the first transmitter being configured to apply a voltage at the bus end to increase the potential difference between at least two conductors of the bus towards the dominant state, the second transmitter being configured to apply a voltage at the bus end to decrease the potential difference between the at least two conductors of the bus towards the recessive state, wherein:

[0014] Based on the length of time being shorter than the predetermined threshold, the signaling detector is configured to deactivate the second transmitter.

[0015] In one or more embodiments, the predetermined threshold is less than 125 nanoseconds.

[0016] In one or more embodiments, the first scheme comprises performing the following operations during a recessive bit duration initiated by the transition, the operations causing the transmitter arrangement to drive the bus from the dominant state to the recessive state:

[0017] When the differential voltage on the CAN bus decreases to the predefined voltage representing the recessive state within a first predetermined time duration (t0 to t1), controlling the impedance control device to provide an output impedance within the predefined range of impedance values in the dominant state; and

[0018] Subsequently, when the differential driving voltage on the CAN bus is maintained at the predefined voltage for a second predetermined duration (t2 to t3) after the first predetermined duration, increasing the output impedance of the impedance control device to the characteristic impedance of the CAN bus, and maintaining the output impedance of the impedance control device at the characteristic impedance of the CAN bus for a third predetermined duration (t3 to t4); and

[0019] And then, when the differential drive voltage on the CAN bus is maintained at the predefined voltage for a fourth predetermined time duration (t4 to t5) after the third predetermined time duration (t2 to t3), increasing the output impedance of the CAN transceiver (220, 420) from the characteristic impedance of the CAN bus to a higher ohmic value.

[0020] In one or more embodiments, the second scheme comprises performing the following operations during the recessive bit duration initiated by the transition, the operations causing the transmitter arrangement to change from the dominant state to the recessive state:

[0021] When the differential voltage on the CAN bus decreases to the predefined voltage within a first predetermined duration (t0 to t1) of the second scheme, controlling the output impedance of the impedance control device to be within the predefined range of impedance values in the dominant state; and

[0022] Subsequently, when the differential voltage on the CAN bus remains at the predefined voltage for a second predetermined duration (t2 to t3) of the second scheme after the first predetermined duration, the output impedance of the impedance control device is directly increased to a high impedance, wherein the high impedance includes an impedance higher than the characteristic impedance of the CAN bus, and the high impedance is maintained for at least a remaining portion or the entire duration of the recessive bit duration.

[0023] In one or more embodiments, the impedance control device comprises an impedance bridge comprising two legs, and wherein each of the two legs comprises an adjustable pull resistor and an adjustable push resistor connected in series between a voltage supply rail and a ground rail and connected to a corresponding one of the two CAN bus terminals.

[0024] In one or more embodiments, the transceiver comprises a receiver arrangement coupled to the two bus ends and configured to receive signaling from the CAN bus, generate digital data, receive data based on the signaling, and provide the received data to a receive output for coupling to the CAN controller.

[0025] In one or more embodiments, the transmitter arrangement is configured to operate at any time in a first transmission mode or a second transmission mode, wherein in the first transmission mode the transmitter arrangement is configured to transmit the signaling with a first property, and when the transmitter arrangement is in the second transmission mode the transmitter arrangement is configured to transmit the signaling with a second property different from the first property;

[0026] Based on the length of time determined by the signalling detector being longer than a predetermined threshold, the transmitter arrangement is configured to operate in the first transmission mode; and

[0027] Based on the length of time determined by the signalling detector being shorter than a predetermined threshold, the transmitter arrangement is configured to operate in the second transmission mode.

[0028] In one or more embodiments, the first property and the second property include one or more of the following:

[0029] respectively comprising a first baud rate for transmitting the signaling and a second baud rate for transmitting the signaling, wherein the second baud rate is greater than the first baud rate;

[0030] and a second voltage level scheme for representing logic one and logic zero in the signaling applied to the CAN bus, wherein the voltage level of the first voltage level scheme is different from the voltage level of the second voltage level scheme.

[0031] According to a second aspect of the present disclosure, we provide a combination of a Controller Area Network (CAN) controller and a CAN transceiver according to any one of the preceding claims, the CAN controller comprising:

[0032] a transmit output configured to provide transmit data to the CAN transceiver for transmission on the CAN bus;

[0033] a receive input configured to receive received data from the CAN transceiver, the data representing signaling received from the CAN bus; and

[0034] a function selector configured to provide the transmission data to a mode signal, the mode signal instructing the CAN transceiver to operate in a second transmission mode instead of the first transmission mode and to disable operation of the impedance control device according to the first scheme, wherein the mode signal includes the controller being configured to provide the transmission data, the transmission data including the logic zero state for a length of time that is less than the predetermined threshold before the transmission data transitions from the logic zero state to the logic one state.

[0035] In one or more embodiments, the CAN controller is configured to provide the transmission data at a second baud rate when the transceiver is in the second transmission mode, the second baud rate being greater than the first baud rate used when the transceiver is in the first transmission mode, and wherein the second baud rate is such that a bit time of the second baud rate is less than the predetermined threshold.

[0036] In one or more embodiments, the CAN controller is configured to provide the transmission data at the first baud rate when the mode signal is not provided, wherein the first baud rate is such that a bit time of the first baud rate is greater than the predetermined threshold, thereby providing operation of the impedance control device according to the first scheme.

[0037] According to a third aspect of the present disclosure, there is provided a method for operating a Controller Area Network (CAN) transceiver, the CAN transceiver comprising two bus ends for coupling the transceiver to a CAN bus and a transmitter arrangement configured to transmit signaling on the CAN bus via the bus ends based on transmission data received at a transmission input, the transmission input comprising a terminal for coupling to a CAN controller, the transmitter arrangement comprising at least one transmitter configured to drive the bus into a dominant state or a recessive state based on a transmission signal, and comprising impedance control means connected to the two bus ends; the method comprising:

[0038] detecting, using a signaling detector, signaling from the controller received at the transmission input along with the transmission data;

[0039] determining the length of time that the transmission data includes the logic zero state before the transmission data transitions from the logic zero state to the logic one state, and:

[0040] Based on the length of time being longer than a predetermined threshold, the impedance control device provides control of the output impedance according to a first scheme, including controlling the output impedance within a predefined range of impedance values in the dominant state when a differential drive voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, and then increasing the output impedance for a first predetermined time duration; and

[0041] Based on the time length being shorter than the predetermined threshold, one of the following operations is provided: controlling the output impedance according to a second scheme different from the first scheme; and the impedance control device not controlling the output impedance.

[0042] While the present disclosure is susceptible to various modifications and alternative forms, details thereof have been shown by way of example in the drawings and will be described in detail. However, it should be understood that other embodiments than the specific ones described are possible. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are also encompassed.

[0043] The above discussion is not intended to present every example embodiment or every implementation within the scope of the current or future claim sets. The figures and detailed description also illustrate various example embodiments. The various example embodiments can be more fully understood by considering the following detailed description in conjunction with the figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0045] Figure 1 An example of a CAN bus network with multiple nodes is shown;

[0046] Figure 2 A first example node is shown;

[0047] Figure 3 A second example node is shown;

[0048] Figure 4 An example transmitter arrangement of a node comprising an impedance bridge is shown;

[0049] Figure 5 Shown Shown Figure 4 Example signal timing diagrams for the operation of the transmitter arrangement depicted in;

[0050] Figure 6 A first example transceiver according to the present disclosure is shown;

[0051] Figure 7 A second example transceiver according to the present disclosure is shown;

[0052] Figure 8 Shown Shown Figure 6 Example signal timing diagrams of the operation of the transceiver depicted in FIG.

[0053] Figure 9 Shown Shown Figure 7 Example signal timing diagrams of the operation of the transceiver depicted in FIG.

[0054] Figure 10 An example flow chart illustrating a method of the present disclosure is shown. DETAILED DESCRIPTION

[0055] A Controller Area Network (CAN) typically includes multiple nodes, each connected to a two-wire CAN bus. The nodes can communicate with each other by sending and receiving signals to and from the CAN bus.

[0056] The Controller Area Network (CAN) is a message-based communication bus protocol commonly used in automobiles. The CAN bus protocol enables communication between various electronic control units (ECUs), such as the engine control module (ECM), powertrain control module (PCM), airbags, anti-roll brakes, cruise control, electric power steering, audio systems, window, door, and mirror adjustment, and battery and recharging systems for hybrid / electric vehicles. The data link layer of the CAN protocol is standardized in International Standards Organization (ISO) 11898-1:2003. CAN Flexible Data-rate, or "CAN FD," an extension of the standardized CAN data link layer protocol and integrated into the ISO 11898-1:2015 standard, offers even higher data rates.

[0057] Figure 1 An example of a bus system or network 100 is shown having a plurality of nodes 101 coupled to communicate via a bus 102 . Figure 2 An example of one of the plurality of nodes 101 is shown in greater detail and like reference numerals are used.

[0058] A plurality of nodes 101, which may also be referred to as "ECUs" or CAN nodes or CAN bus devices, are each connected to a CAN bus 102. In this example, each CAN node includes a controller 110, which may include a microcontroller with an embedded CAN protocol controller 114 and a CAN transceiver 120. The microcontroller is typically connected to at least one device (not shown), such as a sensor, actuator, or some other control device, and is programmed to determine the meaning of a received message and generate an appropriate outgoing message. Microcontrollers are also known in the art as host processors, hosts, or digital signal processors (DSPs). In the example, the host supports application software that interacts with the CAN protocol controller.

[0059] As is known in the art, a CAN protocol controller 114, which may be embedded within the microcontroller 110 or external to the microcontroller (e.g., a separate IC device), implements data link layer operations. For example, in a receive operation, the CAN protocol controller may store serial bits received from the transceiver 120 until the entire message is available for extraction by the microcontroller. The CAN protocol controller may also decode CAN messages according to the standardized frame format of the CAN protocol. In a transmit operation, the CAN protocol controller 114 may be configured to receive messages from the microcontroller 110 and transmit the messages as serial bits (referred to herein as "transmitted data") in a CAN frame format to the CAN transceiver 120.

[0060] The CAN transceiver 120 is located between the controller 110 and the CAN bus 102 and implements physical layer operations. For example, during receive operations, the CAN transceiver converts analog differential signals from the CAN bus into serial digital signals that can be interpreted by the CAN protocol controller 114. The CAN transceiver 120 also protects the CAN protocol controller from extreme electrical conditions on the CAN bus, such as electrical surges. During transmit operations, the CAN transceiver 120 converts the serial digital bits of transmission data received from the CAN protocol controller into analog differential signals that are sent on the CAN bus.

[0061] CAN bus 102 carries analog differential signals and includes a CAN high (CANH) bus conductor 124 and a CAN low (CANL) bus conductor 126. The CAN bus conductors may include a twisted pair of wires. CAN buses are known in the art.

[0062] Therefore, refer to the example Figure 2 Node 101 includes a controller 110, such as a microcontroller. CAN controller 110 uses CAN transceiver 120 to provide signaling to and receive signaling from CAN bus 102. Thus, CAN transceiver 120 typically provides signaling to the CAN bus based on transmission data received from CAN controller 110, and provides received digital data to CAN protocol controller 114 based on the signaling received by CAN transceiver 120 from CAN bus 102. CAN transceiver 120 can be configured to provide signaling to CAN bus 102 using voltage levels suitable for logic high and logic low based on transmission data and using differential signaling suitable for a two-wire CAN bus in accordance with the CAN protocol.

[0063] References herein to a CAN transceiver or CAN controller should be understood as controllers and transceivers that at least partially implement all or part of the CAN protocol or all or part of the CAN FD protocol. The functionality described herein for a CAN transceiver or CAN controller (including its protocol controller) may include more functionality than currently defined in the CAN protocol.

[0064] The CAN controller 110 is configured to provide transmission data at a transmission output 104 for reception at a transmission input 105 of the CAN transceiver 120. The transmission output 104 and the transmission input 105 may comprise integrated circuit pins. Thus, the transmission input pin 105 is configured to receive transmission data from the CAN controller 110. The CAN transceiver 120 is configured to receive signaling from the CAN bus 102 and, based on the signaling, provide received data (as a serial digital data stream) to a receive output 106 for reception at a receive input 107 of the CAN controller 110. The receive output 106 and the receive input 107 may comprise integrated circuit pins.

[0065] The CAN transceiver 120 comprises a transmitter arrangement 108 configured to transmit signalling on the CAN bus 102 based on said transmission data. The CAN transceiver 120 further comprises a receiver arrangement 115 configured to receive signalling from the CAN bus 102 and to provide received data based on said signalling.

[0066] The transmitter arrangement 108 includes at least one transmitter, and in this example, two transmitters 111 and 112. The first transmitter 111 can be configured to drive the bus 102 to a dominant state, thereby representing a logical 0. The second transmitter 112 can be configured to drive the bus 102 (and, in some examples, the first transmitter 111) to a recessive state, thereby representing a logical 1. Each of the transmitters 111 and 112 has two outputs to provide signaling to the two-wire CAN bus 102. It will be appreciated that dominant and recessive states are known to those skilled in the art of CAN. The receiver arrangement 115 includes at least one receiver 116 having two inputs to receive differential signaling from the CAN bus.

[0067] At least one transmitter 111, 112 can be configured to operate in a first transmission mode or a second transmission mode, wherein in the first transmission mode, the transmitter arrangement is configured to transmit the signaling using a first property, and wherein in the second transmission mode, the transmitter arrangement is configured to transmit the signaling using a second property. The first property and the second property may include one or more property types, such as baud rate (e.g., maximum, minimum, or average baud rate), voltage level scheme, encoding scheme, or other. However, for ease of explanation herein, the first property and the second property may include baud rate, such that the first property includes a first baud rate and the second property includes a second baud rate, wherein the second baud rate is higher than the first baud rate. Using a higher baud rate can increase the rate at which data can be transmitted on the CAN bus. However, it should be understood that alternatively, or in addition, the first property and the second property may (in any example embodiment herein) be a voltage level scheme used to represent logic 0 and logic 1 on the CAN bus 102.

[0068] In this example, in a first transmission mode, the transmitter arrangement 108 is configured to transmit signaling at a lower baud rate and to transmit the signaling using a first voltage level scheme to represent logic high and logic low on the CAN bus. In this example, in a second transmission mode, the transmitter arrangement 108 is configured to transmit signaling at a higher baud rate and to transmit the signaling using a second voltage level scheme to represent logic high and logic low on the CAN bus, the second voltage level scheme being different from the first voltage level scheme.

[0069] At least one receiver may be configured to operate in a first reception mode or a second reception mode, wherein in the first reception mode the receiver arrangement 115 is configured to receive signaling from the bus 102 with a first property, and in the second reception mode the receiver arrangement 115 is configured to receive signaling from the bus 102 with a second property. As described above, the property may be any one or more of a baud rate, a voltage level scheme, an encoding scheme, or others.

[0070] In this example, in a first receive mode, the receiver arrangement 115 is configured to receive signaling at a lower baud rate and to receive the signaling using a first voltage level scheme to represent logic highs and logic lows on the CAN bus. In this example, in a second receive mode, the receiver arrangement 115 is configured to receive signaling at a higher baud rate and to receive the signaling using a second voltage level scheme to represent logic highs and logic lows on the CAN bus, the second voltage level scheme being different from the first voltage level scheme.

[0071] The first transmission mode and the first reception mode may comprise modes that follow the voltage levels and timing specified by the CAN FD protocol.The second transmission mode and the second reception mode may comprise modes that are part of an extension of the CAN protocol in which higher baud rates are required.

[0072] Whether the transceiver 120 needs to operate in the second transmission mode instead of the first transmission mode may be determined by the CAN controller 101. In one or more examples, it may be necessary to reliably and robustly signal this requirement to the CAN transceiver 120, and in such a way that the transmitter arrangement 108 and / or the receiver arrangement of the CAN transceiver 120 can reliably and robustly transition between the first transmission mode and the second transmission mode, and vice versa.

[0073] In one or more examples, mode change signaling from the CAN controller 110, sent from the transmit output 104 and received by the CAN transceiver 120, can be used to signal a transmit mode change and / or a receive mode change. Thus, the mode change signaling can be superimposed on, embedded in, or otherwise provided with or between transmit data bits.

[0074] Example Figure 3 An example configuration of the transceiver 120 for receiving mode change signaling is shown. Figure 3 , for simplicity, the transmitter arrangement 108 is shown as having a single transmitter.

[0075] The CAN transceiver 120 may include a detector 300 coupled to the transmit data input pin 105 of the transceiver 120. Additionally, the detector 300 may be coupled to the transmitter arrangement 108 and / or one of the transmitters 111 ( Figure 3 Only one transmitter is shown in the figure. Detector 300 can be coupled to one of the receivers in receiver arrangement 115 and / or receiver 116. Detector 300 can be configured to detect mode change signaling. The output of detector 300 can cause a change in transmission mode and / or a change in reception mode in a number of different ways. For example, the output of detector 300 can be configured to cause different components in transmitter arrangement 108 to be connected to the bus and / or different components in receiver arrangement 115 to be connected to the bus. Alternatively, or in addition, different bias voltages or power levels can be applied to one or more components of transmitter arrangement 108 and / or receiver arrangement 115 to provide a means for transmitting and receiving according to the first property and the second property.

[0076] For example, the detector 300 may include at least one of a timer, a counter, a filter, a state machine, a sampler, and a memory.

[0077] The detector 300 can be configured to detect a mode switching signal within the serial bit stream and, in response to the detection, activate switching between different first and second transmission modes and / or first and second reception modes. The detector 300 can be configured to provide the mode switching signal, for example, superimposed on or embedded in the serial bit stream of the transmitted data. The detector can be configured to detect a plurality of switching signals that, in combination, form the mode switching signal provided by the controller 110 or the protocol controller 114.

[0078] In the example Figure 3 , the transceiver 120 of the node 101 includes a power control 302. The power control 302 may be configured to apply one or more different bias voltages or power levels to one or more components of the transmitter arrangement 108 and / or the receiver arrangement 115 to switch between a first transmission mode and a second transmission mode and / or a first reception mode and a second reception mode.

[0079] In an example, the detector 300 is coupled to the receiver arrangement 115, the transmitter arrangement 108, and to the power control 302. In other examples, the detector 300 may be coupled only to the receiver arrangement 115, only to the transmitter arrangement 108, or only to the power control 302 (or to only two of these three components).

[0080] The detector 300 may be configured to activate switching between different transmission / reception modes of at least one of the transmitter arrangement 108 , the receiver arrangement 115 and the power control 302 in response to the switching signal.

[0081] Mode switching between the first transmission mode and the second transmission mode and / or the first reception mode and the second reception mode may not be the only functionality provided by the CAN transceiver 120 .

[0082] The plurality of CAN nodes 101 connected to the bus 102 may be connected to the terminal impedances 127, 128 at the end CAN nodes (see Figure 1) at different distances. CAN nodes farthest from the termination impedances 127, 128 may cause reflections / ringing on the CAN bus, which can reduce the maximum data rate at which the bus can operate correctly. Other factors, such as CAN bus wire length, may also limit the data rate to a certain speed, which is lower than the speed at which reflections become a problem. However, advances in CAN bus protocols, such as CAN FD, have increased the possible data rate to the point where reflections negatively impact the performance of the CAN bus network. Furthermore, it should be considered that even in well-terminated networks, high capacitive bus loads can negatively impact the transmission rate. With a large number of CAN nodes 101 connected to the CAN bus 102, the transition from dominant to recessive becomes very slow. In addition to capacitive effects, the impedance of wires 124, 126 may vary with temperature, resulting in mismatched bus terminations, which in turn cause reflections, even at the terminated end of the CAN network. In the recessive state, the transmitting node 101 is high impedance. When each node connected to bus 102 adds a maximum capacitance of, for example, 100 pF to the CAN bus and the CAN bus impedance is fixed at 60Ω, the dominant to recessive transition can be no faster than approximately 100 nanoseconds (in the case of a network with ten nodes connected). The more CAN nodes connected to the CAN bus wire, the higher the total capacitance and the longer it takes for the recessive bit transition to occur. For complex topologies, a successful recessive bit transition to a reliable recessive bit level at all nodes may take hundreds of nanoseconds up to, for example, 1 microsecond, including any ringing effects. If a transmission rate of 5 Mbit / s or higher is desired, the bit time is 200 nanoseconds, which may be shorter than the bit transition time and may cause communication failures.

[0083] In one or more examples, CAN transceiver 120 can be configured to control the output impedance of transceiver 102. In one or more examples, by controlling the output impedance, signal reflections, ringing, and any other undesirable signal artifacts on the bus can be controlled.

[0084] Figure 4 An example of the present disclosure is shown, which provides functionality for reducing / suppressing signal reflections / ringing, which can be implemented in CAN and CAN FD network topologies to suppress signal interference and improve signal quality. According to the example, the functionality can be activated based on activation signaling provided by the controller 110 via the transmit output 104 and received by the transceiver 120 via the transmit input pin 105. Thus, the functionality can be signaled by the activation signaling in a manner similar to mode switch signaling, using the same path from the transmit data output 104 to the transmit data input 105 as the transmit data.

[0085] The transceiver 120 is configured to detect activation signaling from the controller 110 within the serial bit stream and activate a function. The transceiver 120 can be configured to detect activation signaling, for example, superimposed on or embedded within the serial bit stream. The activation signaling can include one or more pulses, but in one or more examples, the activation signaling can be provided by a transition of a CAN transceiver of the CAN device from a dominant state to a recessive state. In response to detecting the transition of the CAN transceiver from a dominant state to a recessive state (which can be based on detecting a transition from a logic 0 to a logic 1 in transmitted data from the controller), when a differential drive voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, the output impedance of the CAN transceiver is controlled to be within a predefined range of an impedance value in the dominant state. For example, when the differential drive voltage on the CAN bus decreases to the predefined voltage, the output impedance of the CAN transceiver can be controlled to be within a certain percentage above or below the impedance value in the dominant state (e.g., ±5%, ±10%, or another suitable range of values). The transition of a CAN transceiver from a dominant state to a recessive state in a CAN device can be detected by monitoring the transmission data received at the CAN transceiver at the transmission input 105 and identifying the signal edge of the transmission data signal. By controlling the output impedance of the CAN transceiver to a low impedance (e.g., within a certain percentage of the impedance value in the dominant state) during the ramp-down of the differential drive voltage, energy dissipated into the CAN network can be reduced, thereby reducing reflections on the CAN bus. CAN bus reflection suppression techniques are independent of the CAN bus topology and CAN bus data speed and are applicable to various CAN bus topologies and CAN bus data speeds.

[0086] Figure 4 Depicts Figure 2 or Figure 3 An embodiment of a transmitter arrangement 108 of a CAN transceiver 120 is depicted in FIG. Figure 4 In the example of FIG, the CAN transceiver 120 includes an impedance bridge 430 and an impedance controller 432 configured to control the impedance bridge. By controlling the impedance bridge of the CAN transceiver 120 (e.g., based on a transmit data signal received from the transmit data input pin 105), the impedance of the CAN transceiver 120 can be adjusted independently of the signal response at the CAN bus 102. Therefore, signal reflections / ringing at the CAN bus can be reduced or suppressed by the controllable impedance.

[0087] exist Figure 4In the example depicted in FIG, an impedance bridge 430 is connected to a CANH terminal 401 and a CANL terminal 402, which in turn are coupled to bus conductors 124, 126 of bus 102. The impedance bridge comprises a first leg 426, also referred to as a CANH (side) leg, and a second leg 428, also referred to as a CANL (side) leg. Each leg comprises two controllable impedances (e.g., adjustable capacitors, adjustable resistors, and / or adjustable inductors) having impedance properties that can be dynamically adjusted, for example, by an impedance controller 432. The CANH leg comprises a push impedance unit 410 (e.g., implemented as a push resistor R PUSH1 ) and the pull-type impedance unit 415 (eg, implemented as a pull-type resistor R PULL1 ), the push impedance unit 410 is connected to the common voltage supply rail V CC 460 and CANH terminal 401, the pull impedance unit 415 is connected between CANH terminal 401 and the common ground rail 465. The CANL leg includes a pull impedance unit 425 (eg, implemented as a pull resistor R PULL2 ) and a push impedance unit 420 (eg, implemented as a push resistor R PUSH2 ), the pull-type impedance unit 425 is connected to the common voltage supply rail V CC and CANL terminal 402, and the push impedance unit 420 is connected between the CANL terminal 402 and the common ground rail. Figure 4 In the embodiment shown in FIG, the impedance units 410, 415, 420, and 425 are implemented as resistors. However, in other embodiments, at least one of the impedance units 410, 415, 420, and 425 may be implemented as one or more transistors (MOSFET transistors or bipolar transistors), one or more adjustable capacitors, one or more adjustable inductors, or a combination of one or more adjustable resistors, one or more capacitors, and / or one or more adjustable inductors. In some embodiments, the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 At least one resistor in the resistor ladder is implemented as a resistor ladder or other adjustable resistor network, and the impedance controller 432 can adjust the push resistor R (e.g., by controlling switches (e.g., MOSFET transistors or other active semiconductor devices) within the resistor ladder or other adjustable resistor network to connect or bypass the resistor components). PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2The resistance value of at least one resistor therein. The pins may have a symmetrical resistor configuration with respect to the CANH terminal and the CANL terminal. The CAN bus 404 has a load impedance represented by an equivalent bus impedance R BUS as shown schematically at 480. Typically, based on the above-mentioned typical nominal cable impedance of 120 Ω, assuming that the CAN bus is terminated at each end by a termination resistor R Term = 120 Ω, the bus impedance R BUS has an impedance of approximately 60 Ω. In some embodiments, diodes 450, 451, 452, 453 may be connected in series with each of the impedance units 410, 415, 420, 425 to prevent reverse current from flowing from the CAN bus into the common voltage supply rail and into the common ground rail when there is a bus voltage higher than the supply voltage potential V CC at 460 on the common voltage supply rail or a bus voltage lower than the ground potential (or other reference voltage) on the common ground rail 465. In some embodiments, other schemes are used to prevent reverse current from flowing from the CAN bus 102 into the common voltage supply rail and into the common ground, such as diodes connected in series with the common supply rail 460 and diodes connected in series with the common ground rail 465.

[0088] In some embodiments, the push resistors R PUSH1 and R PUSH2 and the pull resistors R PULL1 and R PULL2 can be adjusted, and their impedance values can be dynamically adjusted based on two parameters x and y. The domain of parameter x may include the value range x = (0, 1), where x = (0, 1) = { 0 < x < 1}, and the domain of parameter y may include the value range y = (0, 2], where y = (0, 2] = { 0 < y ≤ 2}. Parameters x and y are independent of each other. The push impedance value Z PUSH1 of the push resistors R PUSH2 can be expressed as: PUSH can be expressed as:

[0089]

[0090] where Rf represents the reference resistance value. The pull impedance value Z PULL1 of the pull resistors R PULL2 can be expressed as: PULL can be expressed as:

[0091] <000​​​​

[0093]

[0094]

[0095] The total differential impedance of the impedance bridge 430, ie, the driving impedance Z of the CAN transceiver 420 CAN , can be dynamically adjusted to any impedance value between the low-resistance state and the high-resistance state. The low-resistance state is represented by the lowest driving impedance value Z in this paper. CAN =R f Determined, the high resistance state is defined in this paper by Z CAN =∞ indicates. f is the minimum driving impedance value of the CAN transceiver 420. For example, the minimum driving impedance value may be R f =15Ω. It should be noted that in this article, Z CAN =∞, which indicates a high impedance state that may include a maximum drive impedance value in the range of several kilohms or megaohms (e.g., at least 1 kiloohm or at least one megaohm). BUS , driving impedance Z CAN It needs to be high impedance in order to allow the differential bus impedance to reach its nominal value of, for example, 60 Ohms again at the end of the slow bit time.Thus, the multiple between the maximum and minimum drive impedances may be in the range of, for example, a thousand or more.

[0096] The impedance controller 432 can be implemented as a processor, such as a microcontroller. In some embodiments, the impedance controller includes a signal edge detector. In some embodiments, the impedance controller 432 is configured to detect a transition of the CAN transceiver 120 from a dominant state to a recessive state (an example of activation signaling), and in response to detecting the transition of the CAN transceiver from a dominant state to a recessive state, when the differential drive voltage on the CAN bus 102 connected to the CAN transceiver (e.g., a different voltage measured between the CANH terminal 401 and the CANL terminal 402) is reduced to a predefined voltage (e.g., 0V or other suitable voltage level), the output impedance of the impedance bridge (e.g., the impedance measured between the CANH terminal 401 and the CANL terminal 402) is controlled to be within a certain percentage of the impedance value in the dominant state (e.g., by simultaneously adjusting the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2The impedance bridge 430 is configured such that when the differential output voltage decreases to a predefined voltage, the output impedance of the impedance bridge 430 is within a certain percentage above or below the impedance value in the dominant state. For example, when the differential drive voltage on the CAN bus decreases to a predefined voltage, the output impedance of the CAN transceiver can be controlled to be within ±5%, ±10%, or another suitable range of values of the impedance value in the dominant state. In some embodiments, when the differential output voltage decreases to the predefined voltage, the output impedance of the CAN transceiver is controlled to a fixed impedance. By controlling the output impedance of the CAN transceiver to be within a certain percentage above or below the impedance value in the dominant state during the ramp-down of the differential drive voltage, energy dissipated into the CAN network can be reduced under various CAN bus topologies and data speeds, thereby reducing reflections on the CAN bus.

[0097] An active CAN transceiver (i.e., a CAN transceiver in a dominant state) drives the CAN bus waveform to a "dominant" state, represented by a logic low level (logic zero) of the transmission signal. A passive CAN transceiver (i.e., a CAN transceiver in a recessive state) removes its differential output voltage from the CAN bus, represented by a logic high level (logic one) of the transmission signal. Although specific logic levels of the transmission signal are described, in other networks, other signal logic levels may be used. In some embodiments, the impedance controller 432 is configured to control the adjustable push resistor R of the impedance bridge when the differential drive voltage on the CAN bus connected to the CAN transceiver decreases to a predefined voltage. PUSH1 and R PUSH2 And the adjustable pull-in resistor R PULL1 and R PULL2 In an embodiment, during the positive / rising or negative / falling signal edge of the transmission signal, the impedance controller can adjust the adjustable push resistor R PUSH1 and R PUSH2 And the adjustable pull-in resistor R PULL1 and R PULL2 For example, during the dominant (falling) edge of the transmission signal, the impedance controller 432 may adjust the adjustable push resistor R PUSH1 and R PUSH2 The resistance value of the adjustable pull-in resistor R PULL1 and R PULL2 The resistance value of the resistor remains statically high, within a certain percentage of the impedance value above or below the dominant state. In another example, during the recessive (rising) edge of the transmission signal, the impedance controller can independently adjust the adjustable push resistor R with different slopes. PUSH1 and R PUSH2 And the adjustable pull-in resistor R PULL1 and R PULL2The resistance value of each resistor in the impedance bridge is adjusted so that the overall impedance of the impedance bridge remains within a certain percentage above or below the impedance value in the dominant state.

[0098] In some embodiments, the impedance controller 432 is configured to increase the output impedance of the CAN transceiver 420 (e.g., the impedance measured between the CANH terminal 401 and the CANL terminal 402) when the differential drive voltage on the CAN bus 404 (e.g., the different voltages measured between the CANH terminal 401 and the CANL terminal 402) is maintained at a predefined voltage. Because the CAN bus voltage is maintained at a predefined voltage (e.g., 0V) when the output impedance of the CAN transceiver is increased, the impedance change does not cause a large amount of energy to be dissipated into the CAN network, and thus reduces or prevents new reflections on the CAN bus. For example, the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 The at least one resistor in the resistor ladder may be implemented as a resistor ladder or other adjustable resistor network, and the impedance controller may increase the push resistor R (e.g., by controlling switches within the resistor ladder or other adjustable resistor network to connect the resistor components). PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 The impedance controller 423 may increase the output impedance of the CAN transceiver to a value equal to the characteristic impedance of the CAN bus or to a predefined impedance value close to the characteristic impedance of the CAN bus (e.g., ±5%, ±10%, or within another suitable range of values of the characteristic impedance of the CAN bus) when the differential drive voltage on the CAN bus is maintained at a predefined voltage. In some embodiments, before the data sampling time, the impedance controller increases the output impedance of the CAN transceiver to a value equal to the characteristic impedance of the CAN bus or to a predefined impedance value lower than or higher than the characteristic impedance of the CAN bus to avoid data sampling errors. In some embodiments, when the differential drive voltage on the CAN bus is maintained at a predefined voltage, the impedance controller increases the output impedance of the CAN transceiver to a value equal to the characteristic impedance of the CAN bus, and then, when the differential drive voltage on the CAN bus is maintained at the predefined voltage, increases the output impedance of the CAN transceiver from the characteristic impedance of the CAN bus to a high impedance value.

[0099] Figure 5 Shown Figure 4 An example signal timing diagram of the CAN transceiver 120 is depicted in FIG. Figure 5 In the signal timing diagram shown in FIG. 1 , the driving impedance “Z CAN” (e.g., the impedance measured between the CANH terminal 401 and the CANL terminal 402) is controlled by the impedance controller 432 to provide a dominant impedance level “R DOM ”、Active recessive impedance level “R ACTREC ” and the recessive impedance level “R REC The impedance value R can be determined based on the impedance value of the CAN bus 404. DOM 、R ACTREC and / or R REC For example, if the impedance of the CAN bus is 120 ohms, then the impedance value R DOM Can be set to 30 ohms, and the impedance value R ACTREC It can be set to be equal to the impedance value of the CAN bus, that is, 120 ohms. REC It can be set to infinite (∞) and can include a maximum drive impedance value, such as greater than 1 kilo-ohm or greater than 1 megohm.

[0100] In operation, ( Figure 2 The CAN controller 110 of the CAN node 101 (shown in FIG) provides a serial bit stream to the CAN transceiver 120 for transmission on the CAN bus. The impedance controller 432 can monitor the transmission data for activation signaling. In one or more examples, the impedance controller 432 monitors the signal transitions / edges on the transmission data bit stream at the transmission input 105 and adjusts the impedance value of the impedance bridge accordingly.

[0101] The transmission data at time t0, 105 transitions from low to high, which causes the transmitter arrangement to provide a differential voltage V on the CAN bus 404. CAN It will be appreciated that the low-to-high transition of the TXD signal on the TXD path 251 may not immediately cause the CAN bus voltage V CAN This is because there may be a delay when the transmission signal received at the input 105 is converted into the voltage level of the CAN bus. In the dominant state, the impedance controller 432 controls the push resistor R PUSH1 and R PUSH2 To maintain the dominant impedance level (e.g., 15Ω) and control the pull-up resistor R PULL1 and R PULL2 To maintain high impedance, this will produce a dominant impedance level R DOM Low drive impedance Z (e.g. 30Ω) CAN .

[0102] In response to detecting the dominant-to-recessive transition (including an example of an activation signal) at time t0, the impedance controller 432 controls the push resistor R PUSH1 and RPUSH2 And the pull resistor R PULL1 and R PULL2 , to drive the impedance Z CAN For example, between time point t0 and time point t1, when the driving impedance Z CAN When the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 The resistance value of each resistor in the CAN bus changes, so that the CAN bus voltage V CAN From V DOM The impedance controller can make the push resistor R PUSH1 and R PUSH2 The resistance value of the pull-in resistor R is gradually increased from one value (for example, 15 ohms) to a higher value (for example, 30 ohms). PULL1 and R PULL2 The resistance value of the resistor decreases from "infinite" to a certain value (30 ohms). At time point t1, when the driving impedance Z CAN When the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 The resistance values of can be identified to each other. At time t1, the CAN bus voltage V CAN reaches the recessive state (0V), and at time point t0, the impedance controller will drive the impedance Z CAN Controlled as compared to the driving impedance Z CAN The impedance value remains unchanged. CAN After reaching the recessive state (0V), the impedance controller will drive the impedance Z CAN Controlled to be constant during another duration. By setting the driving impedance Z CAN Controlled by the CAN bus voltage V CAN The ramp-down period remains unchanged, which can reduce the energy dissipated into the CAN network, thereby resulting in fewer reflections on the CAN bus 102.

[0103] At time t2, the impedance controller 432 starts to drive the impedance Z CAN From the low resistance R DOM Increases to a higher value until time t3. For example, the push resistor R PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2The at least one resistor in the resistor ladder may be implemented as a resistor ladder or other adjustable resistor network, and the impedance controller may increase the push resistor R (e.g., by controlling switches within the resistor ladder or other adjustable resistor network to connect the resistor components). PUSH1 and R PUSH2 And the pull resistor R PULL1 and R PULL2 At time point t3, the driving impedance Z CAN Reaching the active recessive impedance level R ACTREC , the impedance level can be adjusted to the characteristic impedance of the CAN network cable (for example, 120 ohms) or any other suitable value. CAN When the CAN bus voltage V CAN Keep it at 0V, so the impedance change does not cause a lot of energy to be dissipated into the CAN network, and thus reduce or prevent new reflections on the CAN bus 404. CAN The adjustment of can be performed continuously over time and can increase at a constant rate of change. In some embodiments, the driving impedance Z CAN The constant rate of change is set to be lower than a predefined value to gradually increase the driving impedance Z CAN The impedance controller can be controlled by the push resistor R PUSH1 and R PUSH2 And the pull resistor R Pull1 and R Pull2 To adjust the driving impedance Z CAN , so that the impedance of the resistor is increased from the starting push-type impedance (e.g., Z CAN =30Ω) to the target push impedance (e.g., Z CAN =120Ω). In some embodiments, the impedance controller continuously increases the push resistor R at a constant rate of change over time. PUSH1 and R PUSH2 And the pull resistor R Pull1 and R Pull2 In some embodiments, the duration between time point t1 and time point t2 is zero.

[0104] The reflection on the CAN bus 102 is suppressed until the time point t4. The longer the duration between the time point t0 and the time point t4, the better the ringing suppression performance. At the time point t4, the impedance controller 432 starts to make the driving impedance Z CAN From the active recessive impedance level R ACTREC Increases to a higher value until time point t5. At time point t5, the driving impedance Z CAN Reaching the recessive impedance level R RECIn some embodiments, if the bus voltage is non-zero at time t4, the time between time t4 and time t5 is longer than a certain duration to reduce or prevent additional energy dissipation into the CAN network. For example, if another transmitter is also driving the bus dominant, such as during arbitration or when transmitting an error frame, the bus voltage may be non-zero at time t4. The threshold time duration between t4 and t5 depends on the complexity of the network topology.

[0105] It will be appreciated that backward compatibility between CAN controllers and CAN transceivers, which may have different functionalities, is important. It is also important to reliably signal the use of functionality (i.e., transmit and receive mode switching functionality and impedance control functionality) from the controller 110 to the transceiver 120. In some instances, there may be a conflict between backward compatibility and reliably signaling the use of different functionalities of the transceiver 120, particularly when providing transmit data at the transmit input 105 of the transceiver for mode switching signaling and activation signaling.

[0106] It will be appreciated that a CAN transceiver 120 may have been deployed with only one of impedance control functionality or mode switching functionality, and therefore, there is no opportunity to modify the activation signaling or mode switching signaling to avoid conflict when both are required.

[0107] In one or more examples, it may be desirable to reliably signal different functionalities to the CAN transceiver 120 while maintaining backward compatibility.

[0108] Figure 6A CAN transceiver according to the present disclosure is shown. The transceiver 600 includes two bus terminals 601, 602 for coupling the transceiver to a CAN bus 102. The transceiver includes a transmitter arrangement 603 configured to transmit signaling on the CAN bus 102 via the bus terminals 601, 602 based on transmission data received at a transmission input 604. The transmission input includes a terminal for coupling to a CAN controller (shown as 110 in the previous figure). The transmitter arrangement 603 includes at least one transmitter configured to drive the bus to a dominant state or a recessive state based on the transmission signal. In this example and other examples, the transmitter arrangement 603 includes two transmitters 605 and 606. The first transmitter 605 can be configured to drive the bus 102 to a dominant state, thereby representing a logic 0 of the transmission data on the CAN bus. The second transmitter 606 can be configured to drive the bus 102 and the first transmitter 605 to a recessive state, thereby representing a logic 1 of the transmission data on the CAN bus. Each of the transmitters 605, 606 has two outputs to provide signaling to the two terminals 601, 602. The first transmitter can be referred to as a push transmitter because it pushes the different potentials between the bus conductors to a dominant state. The second transmitter can be referred to as a pull transmitter because it pulls the different potentials between the bus conductors to a recessive state.

[0109] The transmitter arrangement 603 further comprises an impedance control device 607 connected to the two bus terminals. The impedance control device 607 is configured to control the output impedance of the transceiver by controlling the output impedance of the transmitter arrangement 603 at the bus terminals 601, 602. The impedance control device may be embodied as control blocks 614, 615 and the first transmitter 605 and the second transmitter 606. The arrangement may be implemented as Figure 4 4. In such an embodiment, the control block 607 may perform the function of the impedance controller 432. It will be appreciated that variations in the structure of the impedance bridge described above are applicable in this embodiment. Additionally, it will be appreciated that other than the output impedance of the transmitter arrangement 603 and the transceiver 600 may be provided for controlling the output impedance of the transmitter arrangement 603 and the transceiver 600 as a whole. Figure 4 In summary, each impedance control block 614, 615 can control both the first transmitter 605 and the second transmitter 606 to control the output impedance of the transceiver while applying the explicit signaling and the implicit signaling to the buses 601, 602.

[0110] In the example Figure 6, the transceiver 600 includes a receiver arrangement 608 coupled to the two bus terminals 601, 602 and configured to receive signaling from the CAN bus. The receiver arrangement 608 may include one or more receivers 610 configured to generate a received digital data signal based on the CAN bus signaling. The received data is provided to a receive output 611 for coupling to the CAN controller 110.

[0111] The transceiver 600 includes a signaling detector (combination of 612, 613) configured to detect signaling received along with the transmission data at the transmission input 604 from the controller 110. The signaling detector is configured to determine the length of time that the transmission data includes a logic zero state before the transmission data transitions from the logic zero state to the logic one state. Thus, in one or more examples, the signaling detector can include a time filter 612 for this purpose.

[0112] Generally speaking, transceiver 600 is configured to:

[0113] Based on the length of time being longer than a predetermined threshold, providing control of the output impedance by the impedance control device according to a first output impedance control scheme (eg, provided by the first control block 614); and

[0114] Based on the time length being shorter than the predetermined threshold, any one of the following operations is provided: (1) controlling the output impedance according to a second output impedance control scheme (e.g., provided by the second control block 615) that is different from the first scheme; and (2) the impedance control device does not actively control the output impedance (see example Figure 7 ).

[0115] The impedance control scheme includes making one or more output impedance changes and maintaining the output impedance over time when and after the transmitter arrangement 603 drives the bus to the recessive state.

[0116] refer to Figure 5 , the first solution involves the differential voltage V CAN When the voltage is reduced to a predetermined voltage shown as 0 volts during the time period t0 to t1, the output impedance is controlled to an impedance value (R DOM ). Thus, the predefined voltage includes a voltage that places the bus in a recessive state (less than 0.5 volts according to the CAN protocol). The first approach then includes increasing the output impedance over a first predetermined time duration, shown as t1 to t5. That is, the first predetermined time duration includes the time it takes to reach the maximum output impedance provided by the impedance control device within the bit time 500 that begins once the bus reaches the recessive state. The increase includes first increasing to R ATREC, and maintain R in the next period t3 to t4 ATREC After the period of t4 to t5, it increases to R REC Thus, in summary, the increase comprises two separate increases within the recessive bit time 500 separated by a period of substantially constant output impedance. Figure 5 This first approach is described in more detail in the description of .

[0117] In one or more examples, controlling transceiver functionality based on signaling provided at transmit input 604 and transmit data is advantageous because existing pins / terminals are reused, eliminating the need for hardware changes. However, as the functionality of a CAN transceiver increases and more and more "function activation" signals need to be signaled by the CAN controller to the transceiver, signaling activation / deactivation of functionality while maintaining backward compatibility with potentially released functionality becomes more difficult. It may be desirable for a CAN controller and a CAN transceiver (having different functionality available for each) to be compatible with each other because signaling from the CAN controller to the CAN transceiver should activate desired functionality rather than undesired functionality.

[0118] It may be advantageous to use the length of time that a logic zero state remains before a transition to transmit data to select between operating the output impedance control using the first scheme and not using the first scheme. Thus, output impedance control using the first scheme can still be provided for CAN controllers that are unable to provide bit times shorter than a predetermined threshold. However, CAN controllers that may wish to use a higher baud rate (and therefore do provide bit times shorter than the predetermined threshold) and may not wish to activate the first scheme impedance control can effectively signal this to the CAN transceiver 600.

[0119] Using this approach to enable transmission of data at higher baud rates can be particularly advantageous, as the predetermined threshold time can be selected to be shorter than the shortest bit time provided by legacy protocols. For example, CAN FD has a maximum baud rate of 8 Mbps, which results in a minimum bit time of 125 nanoseconds. If a baud rate higher than the maximum baud rate of CAN FD needs to be signaled from a CAN controller to a CAN transceiver, then using a predetermined threshold time of less than 125 nanoseconds can be advantageous, as legacy controllers do not provide signaling with bit times shorter than 125 nanoseconds, and new functionality can be reliably signaled while maintaining backward compatibility.

[0120] In one or more examples, the signaling detector can be provided by a digital signal processor configured to determine the bit time before the transition from logic 0 to logic 1 and control the impedance control device accordingly. However, in this example, the signaling detector includes a time filter 612 configured to provide a switching signal based on whether the time length is longer or shorter than a predetermined threshold, wherein the signaling detector further includes a multiplexer 613 configured to receive the switching signal and switch between the following states based on the switching signal:

[0121] a first state in which the multiplexer is configured to connect the first control block 614 to provide signaling to the remainder of the impedance control device to provide a first scheme; and

[0122] A second state, in which the multiplexer is configured to: connect the second control block 615 to provide signaling to the rest of the impedance control device to provide the second scheme; or disconnect the first control block 615 from the impedance control device.

[0123] Therefore, the example Figure 6 An arrangement is shown in which a first control block 614 or a second control block 615 is connected to the impedance control device to provide control according to the first or second scheme, respectively. Figure 6 An embodiment is shown in which the signalling detectors 612, 613 are configured to provide control of the output impedance according to a second scheme provided by the control block 615 based on the length of time being shorter than the predetermined threshold.

[0124] Example Figure 7 Basically similar to Figure 6 The same reference numerals have been used. However, in this example, the second control block 615 is not present, and therefore, the multiplexer 613 is used to disconnect the first control block 614 from the impedance control device. The transmitter arrangement 603 is then configured to transmit signaling to the bus based on the transmission data, without the impedance control device actively controlling the impedance.

[0125] In one or more examples, impedance control according to the first scheme can be provided by the second transmitter 606. Therefore, the signaling detectors 612, 613 can be configured to deactivate the second transmitter 606 based on the length of time being shorter than the predetermined threshold.

[0126] Already about Figure 5 A first approach is described, however, an overview is provided below. Figure 5, the first scheme comprises the following impedance control during a recessive bit duration 500, which is initiated by a transition 501 from a logic 0 in the transmitted data at 502 (which causes the transmitter arrangement to apply a dominant state to the bus) to a logic 1 in the transmitted data at 604 (which causes the transmitter arrangement to apply a recessive state to the bus).

[0127] First, when the differential voltage on the CAN bus decreases to a predefined voltage within a first predetermined time duration between t0 and t1, the output impedance of the impedance control device is controlled to an impedance value R in a dominant state. DOM Therefore, when the V CAN The differential voltage from V DOM When it decreases to 0V, the output impedance Z CAN Basically maintain at R DOM The predefined voltage includes a differential bus voltage representing a recessive state. Immediately after the differential driving voltage on the CAN bus has decreased to the predefined voltage between t1 and t2, the output impedance of the impedance control device can be controlled to an impedance value R in a dominant state. DOM within a predefined range.

[0128] Then, when the differential voltage V CAN When the output impedance remains at a predefined voltage (eg, 0 V) for a second predetermined duration between t2 and t3 after the first predetermined duration, the impedance control device may be configured to increase the output impedance to the characteristic impedance R of the CAN bus. ACTREC .

[0129] Subsequently, the impedance control device may be configured to maintain the output impedance at the characteristic impedance of the CAN bus during a third predetermined time duration t3 to t4.

[0130] Subsequently, the impedance control device may be configured to reduce the output impedance from the characteristic impedance R of the CAN bus to the predetermined voltage when the differential voltage on the CAN bus is maintained at the predetermined voltage for a fourth predetermined time duration t4 to t5 after the third predetermined time duration (t2 to t3). ACTREC Increase to higher ohmic values R REC Impedance value R REC It can be greater than 1 kilo-ohm or greater than 1 megohm.

[0131] It will be appreciated that the first control block 614 may provide signaling to the impedance bridge to control the output impedance of the CAN transceiver to within a certain percentage above or below the impedance value in the dominant state (other impedance values described above).

[0132] Figure 8 Shown in Figure 6. In this example, the signaling detector detects a transition of the transmitted data at 801 from a logic zero to a logic one. The length of time 802 during which the transmitted data included a logic zero state prior to the transition at 801 is shorter than the predetermined threshold in this example diagram. Therefore, the signaling detector connects the second control block 615 to the impedance control block to provide a second solution.

[0133] Generally speaking, the second scheme consists in switching on the CAN bus when the differential voltage on the CAN bus decreases to a predefined voltage (at Figure 8 between t0 and t1 in the first embodiment), the output impedance is controlled within a predefined range of the impedance value in the dominant state, and then for a second predetermined time period ( Figure 8 The output impedance is increased from t1 to t2 in the first solution, wherein the second predetermined time duration is shorter than the first predetermined time duration for increasing the output impedance in the first solution. Figure 5 The second predetermined time duration includes reaching the maximum output impedance provided by the impedance control device, i.e., R REC , the time spent.

[0134] In more detail, the second solution may first include: Figure 8 When the voltage decreases to a predefined voltage within the first predetermined time period from t0 to t1, the output impedance of the impedance control device is controlled within a predefined range of impedance values in the dominant state.

[0135] The second approach may then include the following: when the differential voltage on the CAN bus is Figure 8 When the output impedance of the impedance control device is maintained at the predefined voltage for the second predetermined time period (t1 to t2), the output impedance of the impedance control device is directly increased to the high impedance R REC , the high impedance R REC Including higher than the characteristic impedance R of the CAN bus ACTREC The impedance of t2 is maintained at a high impedance for at least the remainder or all of the recessive bit duration, ie after time t2. It will be appreciated that for clarity, Figure 8 The length of the recessive state may be shown to be longer than a single bit time.

[0136] Figure 9 Shown in Figure 7 1. Example of operation of an embodiment of the present invention. In this example, the signaling detector detects a transition of the transmission data from a logic zero to a logic one at 901. The length of time 902 during which the transmission data includes a logic zero state before the transition at 901 is shorter than the predetermined threshold in this example diagram. In this example, there is no control of the output impedance by the impedance control device, and therefore, the transmitter is arranged so that the CAN bus V CANThe differential voltage on t0 decreases to a predefined voltage (indicating a recessive state) within a first predetermined duration between t0 and t1. Output impedance Z CAN During the same period, it increases to a high value R REC .

[0137] It will be appreciated that the second solution can be controlled by Figure 5 The second control block 615 of the impedance bridge is provided. As explained above, the impedance bridge may include two legs, and each of the two legs includes an adjustable pull resistor and an adjustable push resistor connected in series between a voltage supply rail and a ground rail and connected to a respective one of the two CAN bus terminals. The second control block 615 (and the first control block 614 in the previous example) can provide a signal for controlling the value of the adjustable resistor to provide the output impedance.

[0138] In another example, the signaling detector is configured to determine a length of time that the transmitted data includes a logic zero state before the transmitted data transitions from the logic zero state to the logic one state, and may be configured to activate other functions.

[0139] Thus, the transmitter arrangement may be configured to operate at any time in a first transmission mode or a second transmission mode, wherein in the first transmission mode the transmitter arrangement is configured to transmit said signalling with a first property, and when the transmitter arrangement is in the second transmission mode the transmitter arrangement is configured to transmit said signalling with a second property different from the first property; wherein

[0140] Based on the length of time determined by the signalling detector being longer than a predetermined threshold, the transmitter arrangement is configured to operate in a first transmission mode; and

[0141] Based on the length of time determined by the signalling detector being shorter than a predetermined threshold, the transmitter arrangement is configured to operate in the second transmission mode.

[0142] In this example, the primary and secondary properties include:

[0143] respectively comprising a first baud rate for transmitting the signaling and a second baud rate for transmitting the signaling, wherein the second baud rate is greater than the first baud rate; and

[0144] Respectively including a first voltage level scheme for representing logic one and logic zero in signaling applied to a CAN bus and a second voltage level scheme for representing logic one and logic zero in signaling applied to the CAN bus, wherein the voltage level of the first voltage level scheme is different from the voltage level of the second voltage level scheme.

[0145] In one or more examples, the first baud rate and the first voltage level scheme can comply with the CAN or CAN FD protocol. In one or more examples, the second baud rate can be greater than a maximum value specified by the CAN FD protocol.

[0146] About Figure 1-3 The switching between the first transmission mode and the second transmission mode and the first reception mode and the second reception mode is described in detail.

[0147] In one or more examples, a controller area network (CAN) controller can be provided in combination with the CAN transceiver 600. The CAN controller includes a transmit output node configured to provide transmit data to the CAN transceiver for transmission on the CAN bus, and a receive input configured to receive receive data from the CAN transceiver, the data representing signaling received from the CAN bus. A controller, such as a portion of the microcontroller 110 or the protocol controller 114, can also include a function selector configured to provide the transmit data to a mode signal, the mode signal instructing the CAN transceiver to operate in a second transmit mode instead of the first transmit mode and to disable operation of the impedance control device according to the first scheme, wherein the mode signal includes the controller being configured to provide the transmit data, the transmit data including the logic zero state for a length of time less than a predetermined threshold before the transmit data transitions from the logic zero state to the logic one state.

[0148] The CAN controller can be configured to provide transmission data at a second baud rate when the transceiver is in the second transmission mode, the second baud rate being greater than the first baud rate used when the transceiver is in the first transmission mode. In one or more examples, the second baud rate is such that a bit time of the second baud rate is less than a predetermined threshold used by a signaling detector. However, in other examples, the bit time of the second baud rate is equal to or greater than the predetermined threshold used by the signaling detector.

[0149] The CAN controller may be configured to provide transmission data at a first baud rate when the mode signal is not provided, wherein the first baud rate is such that a bit time of the first baud rate is greater than a predetermined threshold, thereby providing operation of the impedance control device according to the first scheme.

[0150] Figure 10An example method for operating a Controller Area Network (CAN) transceiver is shown, the CAN transceiver comprising two bus terminals 601, 602 for coupling the transceiver to a CAN bus and a transmitter arrangement 603 configured to transmit signaling on the CAN bus via the bus terminals based on transmission data received at a transmission input 604, the transmission input 604 comprising a terminal for coupling to a CAN controller, the transmitter arrangement comprising at least one transmitter configured to drive the bus into a dominant state or a recessive state based on the transmission signal, and comprising impedance control means connected to the two bus terminals; the method comprising:

[0151] Using a signaling detector, detecting 1001 signaling from a controller received at a transmission input together with transmission data;

[0152] determining 1002 a length of time that the transmitted data includes the logic zero state before the transmitted data transitions from the logic zero state to the logic one state, and:

[0153] Based on the length of time being longer than a predetermined threshold, providing 1003 control of the output impedance by the impedance control device according to a first scheme, including controlling the output impedance within a predefined range of impedance values in a dominant state when a differential driving voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, and then increasing the output impedance for a first predetermined time duration; and

[0154] Based on the length of time being shorter than the predetermined threshold, providing 1004 one of the following operations: controlling the output impedance according to a second scheme different from the first scheme; and the impedance control device not controlling the output impedance.

[0155] Unless a particular order is explicitly stated, the instructions and / or flowchart steps in the above figures may be executed in any order. Furthermore, those skilled in the art will recognize that although one example instruction set / method has been discussed, the materials in this specification may be combined in various ways to produce other examples and should be understood within the context provided in this detailed description.

[0156] In some example embodiments, the instruction sets / method steps described above are implemented as functions and software instructions embodied as executable instruction sets that are implemented on a computer or a machine programmed and controlled by the executable instructions. Such instructions are loaded for execution on a processor (e.g., one or more CPUs). The term processor includes a microprocessor, a microcontroller, a processor module or subsystem (including one or more microprocessors or microcontrollers), or other control or computing devices. A processor may refer to a single component or a plurality of components.

[0157] In other examples, the instruction sets / methods described herein and the data and instructions associated therewith are stored in corresponding storage devices that are implemented as one or more non-transient machine or computer-readable or computer-usable storage media. Such computer-readable or computer-usable storage media are considered part of an article (or product). An article or product may refer to any manufactured single component or multiple components. Non-transient machine or computer-usable media as defined herein do not include signals, but such media may be capable of receiving and processing information from signals and / or other transient media.

[0158] Example embodiments of the materials discussed in this specification may be implemented in whole or in part via networks, computers, or data-based devices and / or services. These networks, computers, or data-based devices and / or services may include the cloud, the Internet, an intranet, a mobile device, a desktop computer, a processor, a lookup table, a microcontroller, a consumer device, an infrastructure, or other enabling devices and services. As used herein and in the claims, the following non-exclusive definitions are provided.

[0159] In one example, one or more instructions or steps discussed herein are automated. The terms automation or automatically (and similar variations thereof) refer to the controlled operation of equipment, systems, and / or processes using computers and / or mechanical / electrical devices without the need for human intervention, observation, effort, and / or decision-making.

[0160] It should be understood that any components that are said to be coupled can be coupled or connected directly or indirectly. In the case of an indirect coupling, additional components may be placed between the two components that are said to be coupled.

[0161] In this specification, example embodiments have been presented in terms of a selected set of details. However, those skilled in the art will appreciate that many other example embodiments can be practiced that include different selected sets of these details. It is intended that the appended claims cover all possible example embodiments.

Claims

1. A controller area network (CAN) transceiver, characterized in that: include: two bus terminals, the two bus terminals being used to couple the transceiver to a CAN bus; a transmitter arrangement configured to transmit signaling on the CAN bus via the bus terminals based on transmission data received at a transmission input, the transmission input comprising a terminal for coupling to a CAN controller, the transmitter arrangement comprising at least one transmitter configured to drive the bus into a dominant state or a recessive state based on a transmission signal, and comprising impedance control means connected to the two bus terminals; a signaling detector configured to detect signaling received at the transmission input with the transmission data from the controller, the signaling detector configured to determine a length of time the transmission data includes the logic zero state before the transmission data transitions from the logic zero state to the logic one state, and: providing, by the impedance control device, control of the output impedance according to a first scheme based on the length of time being longer than a predetermined threshold, comprising controlling the output impedance within a predefined range of impedance values in the dominant state when a differential drive voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, and then increasing the output impedance for a first predetermined time duration, the increase comprising two separate increases separated by periods of constant output impedance within a bit time of the logic one state; and Based on the time length being shorter than the predetermined threshold, provide one of the following operations: The output impedance is controlled according to a second scheme different from the first scheme; and the impedance control means does not control the output impedance.

2. The transceiver according to claim 1, wherein: The signaling detector includes a time filter configured to provide a switching signal based on the length of time being longer or shorter than the predetermined threshold, wherein the signaling detector further includes a multiplexer configured to receive the switching signal and switch between the following states based on the switching signal: a first state in which the multiplexer is configured to connect a first control block to provide signaling to the impedance control device to provide the first scheme; as well as a second state, in which the multiplexer is configured to: connect a second control block to provide signaling to the impedance control device to provide the second scheme; Or disconnect the first control block from the impedance control device.

3. The transceiver according to claim 2, wherein: Based on the length of time being shorter than the predetermined threshold, the signaling detector is configured to provide control of the output impedance according to the second scheme.

4. A transceiver according to any preceding claim, characterized in that The transmitter arrangement comprises a first transmitter configured to apply a voltage at the bus end to increase the potential difference between at least two conductors of the bus towards the dominant state, and a second transmitter configured to apply a voltage at the bus end to decrease the potential difference between the at least two conductors of the bus towards the recessive state, wherein: Based on the length of time being shorter than the predetermined threshold, the signaling detector is configured to deactivate the second transmitter.

5. The transceiver according to any one of claims 1 to 3, wherein: The predetermined threshold is less than 125 nanoseconds.

6. The transceiver according to any one of claims 1 to 3, characterized in that: The first scheme comprises performing the following operations during a recessive bit duration initiated by the transition, the operations causing the transmitter arrangement to drive the bus from the dominant state to the recessive state: controlling the impedance control device to provide an output impedance within the predefined range of impedance values in the dominant state when the differential voltage on the CAN bus decreases to the predefined voltage representing the recessive state within a first predetermined duration; as well as Subsequently, when the differential driving voltage on the CAN bus is maintained at the predefined voltage for a second predetermined duration after the first predetermined duration, increasing the output impedance of the impedance control device to the characteristic impedance of the CAN bus, and maintaining the output impedance of the impedance control device at the characteristic impedance of the CAN bus for a third predetermined duration; as well as And then, when the differential drive voltage on the CAN bus remains at the predefined voltage for a fourth predetermined duration after the third predetermined duration, increasing the output impedance of the CAN transceiver from the characteristic impedance of the CAN bus to a higher ohmic value.

7. The transceiver according to any one of claims 1 to 3, wherein: The second scheme comprises performing the following operations during the recessive bit duration initiated by the transition, the operations causing the transmitter arrangement to change from the dominant state to the recessive state: When the differential voltage on the CAN bus decreases to the predefined voltage within the first predetermined duration of the second scheme, controlling the output impedance of the impedance control device to be within the predefined range of impedance values in the dominant state; as well as Subsequently, when the differential voltage on the CAN bus remains at the predefined voltage for a second predetermined duration of the second scheme after the first predetermined duration, the output impedance of the impedance control device is directly increased to a high impedance, wherein the high impedance includes an impedance higher than the characteristic impedance of the CAN bus, and the high impedance is maintained for at least a remaining portion or the entire duration of the recessive bit duration.

8. The transceiver according to any one of claims 1 to 3, characterized in that: The impedance control device comprises an impedance bridge comprising two legs, and wherein each of the two legs comprises an adjustable pull resistor and an adjustable push resistor connected in series between a voltage supply rail and a ground rail and connected to a respective one of the two CAN bus terminals.

9. A combination of a Controller Area Network (CAN) controller and a CAN transceiver according to any one of the preceding claims, characterized in that: The CAN controller comprises: a transmit output configured to provide transmit data to the CAN transceiver for transmission on the CAN bus; a receive input configured to receive received data from the CAN transceiver, the data representing signaling received from the CAN bus; and a function selector configured to provide the transmission data to a mode signal, the mode signal instructing the CAN transceiver to operate in a second transmission mode instead of the first transmission mode and to disable operation of the impedance control device according to the first scheme, wherein the mode signal includes the controller being configured to provide the transmission data, the transmission data including the logic zero state for a length of time that is less than the predetermined threshold before the transmission data transitions from the logic zero state to the logic one state.

10. A method for operating a Controller Area Network (CAN) transceiver, characterized in that: the CAN transceiver comprising two bus ends for coupling the transceiver to a CAN bus and a transmitter arrangement configured to transmit signaling on the CAN bus via the bus ends based on transmission data received at a transmission input, the transmission input comprising a end for coupling to a CAN controller, the transmitter arrangement comprising at least one transmitter configured to drive the bus into a dominant state or a recessive state based on a transmission signal, and comprising impedance control means connected to the two bus ends; The method comprises: detecting, using a signaling detector, signaling from the controller received at the transmission input along with the transmission data; determining a length of time the transmission data includes the logic zero state before the transmission data transitions from the logic zero state to the logic one state, and: providing, by the impedance control device, control of the output impedance according to a first scheme based on the length of time being longer than a predetermined threshold, comprising controlling the output impedance within a predefined range of impedance values in the dominant state when a differential drive voltage on a CAN bus connected to the CAN transceiver decreases to a predefined voltage, and then increasing the output impedance for a first predetermined time duration, the increase comprising two separate increases separated by periods of constant output impedance within a bit time of the logic one state; and Based on the time length being shorter than the predetermined threshold, provide one of the following operations: The output impedance is controlled according to a second scheme different from the first scheme; and the impedance control means does not control the output impedance.

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