Method and apparatus for inhibiting ringing in a controller area network (CAN) bus

Abstract

A circuit for suppressing ringing in a controller area network (CAN) bus having a CAN high (CANH) line and a CAN low (CANL) line is provided. The circuit can include processing circuitry to generate a CAN control signal and a transconductance amplifier to receive a first input signal corresponding to the CAN control signal and a voltage signal from the CANL line and to generate an output current signal based on a difference between the first input signal and the voltage signal from the CANL line. An output terminal of the transconductance amplifier can be coupled to the CANH line to provide current to or sink current from the CANH line.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Nonprovisional Patent Application No. 18 / 986,396, filed December 18, 2024, and U.S. Provisional Patent Application No. 63 / 611,662, filed December 18, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure generally relates to driver circuitry for a Controller Area Network (CAN) bus, and more specifically to methods and apparatus for suppressing ringing in a CAN bus caused by mismatched characteristic impedance. Summary of the Invention

[0003] According to one or more examples, a circuit is provided for suppressing ringing in a Controller Area Network (CAN) bus having a CAN high (CANH) line and a CAN low (CANL) line. The circuit may include: processing circuitry for generating a CAN control signal; and a transconductance amplifier for receiving a first input signal corresponding to the CAN control signal and a voltage signal from the CANL line, and for generating an output current signal based on the difference between the first input signal and the voltage signal from the CANL line. The output terminal of the transconductance amplifier may be coupled to the CANH line to supply current to or draw current from the CANH line. The circuit may further include: a CAN low driver coupled to the processing circuitry, ground or a common node, and the CANL line of the CAN bus; a CAN high driver coupled to the processing circuitry, a power supply voltage, and the CANH line of the CAN bus; and a terminating resistor coupled between the CANH and CANL lines of the CAN bus. The CAN low driver can be coupled to a circuit that simulates CAN bus ringing via the CANL line of the CAN bus, and the CAN high driver can be coupled to a circuit that simulates CAN bus ringing via the CANH line of the CAN bus.

[0004] This transconductance amplifier can receive a gain control signal to control its gain and can generate an output current signal based on the gain control signal. The gain control signal can correspond to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function. The exponential function can be e^(-π / 2)... xThe hyperbolic function can be cosh(x), where x is the input voltage of the CAN bus. The gain control signal can be equivalent to the CAN control signal. The circuit may also include a conversion circuit to convert the current signal into a voltage signal. The CAN control signal can be a signal corresponding to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function, and the conversion circuit can convert the CAN control signal into a voltage signal that is input to the transconductance amplifier as the first input signal. The exponential function can be e x Furthermore, the hyperbolic function can be cosh(x), where x is the input voltage of the CAN bus.

[0005] According to one or more examples, a method for suppressing ringing in a Controller Area Network (CAN) bus, the CAN bus having a CAN high (CANH) line and a CAN low (CANL) line, is provided. The method may include: generating a CAN control signal; receiving a first input signal corresponding to the CAN control signal and a voltage signal from the CANL line; generating an output current signal based on the difference between the first input signal and the voltage signal from the CANL line; and supplying current to the CANH line or drawing current from the CANH line based on the output current signal. The method may further include receiving a gain control signal, and the output current signal may be generated based on the gain control signal. The gain control signal may correspond to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function. The exponential function may be e^(-ε / ε). x The hyperbolic function can be cosh(x), where x is the input voltage of the CAN bus. The gain control signal can be equivalent to the CAN control signal. The CAN control signal can be a current signal corresponding to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function, and the method can include converting the CAN control signal into a voltage signal received as a first input signal. The exponential function can be e x Furthermore, the hyperbolic function can be cosh(x), where x is the input voltage of the CAN bus. Attached Figure Description

[0006] Figure 1 Circuit diagrams are shown for suppressing ringing in a Controller Area Network (CAN) bus, according to various examples.

[0007] Figure 2 It shows according to Figure 1 Circuit diagram of the CAN low (CANL) driver.

[0008] Figure 3 It shows according to Figure 1 Circuit diagram of the CAN high (CANH) driver.

[0009] Figure 4 It shows according to Figure 1 The circuit diagram of the transconductance amplifier. Detailed Implementation

[0010] Reference will now be made to the various examples illustrated in the accompanying drawings, in which the same reference numerals always denote the same elements. These examples may be presented in various forms, and are not limited to those described herein.

[0011] The CAN bus is used in a variety of applications to allow multiple devices to communicate with each other using a common bus. Perhaps the most common use of the CAN bus is in automobiles, allowing various controllers, processors, sensors, and other devices to send and receive information using a single bus. The CAN bus consists of two wires: a CAN low (CANL) line and a CAN high (CANH) line, with a differential signal generated between the two lines.

[0012] The CAN bus is typically driven by a current waveform. When the current through the CAN bus oscillates between parasitic inductance and capacitance, characteristic impedance mismatch in the CAN bus can cause ringing. Ringing can be particularly noticeable during waveform transitions. Therefore, it is necessary to suppress ringing in the CAN bus.

[0013] Figure 1 A circuit diagram of circuit 100 for suppressing ringing in a CAN bus, according to various examples, is shown. Figure 1 The circuit 100 may include processing circuitry 101, such as, but not limited to, a general-purpose or special-purpose processor, microprocessor, controller, or microcontroller, to generate CAN control waveforms. Processing circuitry 101 may be coupled to a CANH driver 102, which is coupled to the power supply voltage and the CANH line of the CAN bus. Processing circuitry 101 may also be coupled to a CANL driver 103, which is coupled to ground or a common node and the CANL line of the CAN bus. A terminating resistor 104 is coupled between the CANH and CANL lines of the CAN bus.

[0014] According to various examples, the processing circuit 101 can receive an input voltage x and can generate a CAN control signal based on the received input voltage x. According to various examples, the CAN control signal can be a current signal or a voltage signal. According to various examples, the CAN control signal can correspond to an exponential function (e.g., e^x). x The ratio of the first signal corresponding to the hyperbolic function (e.g., cosh(x)) and the second current signal corresponding to the hyperbolic function (e.g., cosh(x)). However, various examples can generate other CAN control voltage or current signals.

[0015] Figure 1Circuit 100 may further include an operational transconductance amplifier 105 having a first input for receiving a CAN control signal from processing circuit 101. According to various examples where the CAN control signal is a voltage signal, a CAN control voltage signal may be input to the first input of operational transconductance amplifier 105. According to examples where the CAN control signal is a current signal (e.g., corresponding to an exponential function (e.g., e^(-1 / 2))... x Various examples of circuits for converting current signals into voltage signals, such as diode-connected transistors discussed further below, can be used to convert CAN control current signals into corresponding voltage signals.

[0016] Figure 1 The operational transconductance amplifier 105 may also have a second input to receive a voltage signal from the CANL line of the CAN bus. The operational transconductance amplifier 105 can generate an output current signal based on the difference between the CAN control signal and the voltage signal from the CANL line. According to various examples, the operational transconductance amplifier 105 may receive a gain control signal to control the gain of the operational transconductance amplifier 105. For example, the gain control signal may be a CAN control signal such that the gain of the operational transconductance amplifier 105 is proportional to the CAN control signal. The generated output current signal can be provided to the CANH line of the CAN bus to provide or absorb current at the CANH driver stage. By providing or absorbing current proportional to the difference between the CAN control signal and the voltage signal on the CANL line to the CANH driver stage, the output current signal can cancelily interfere with current oscillations between parasitic capacitances and inductances on the CAN bus to suppress ringing.

[0017] Figure 2 It shows according to Figure 1 The circuit diagram 200 for the CANL driver 103 includes several components, some of which will not be discussed in detail here to avoid obscuring other aspects of the circuit. Figure 2 As shown, the CANL driver 103 may include a first field-effect transistor (FET) 201, the drain of which may be coupled to the CANL line of the CAN bus and circuitry for simulating CAN bus ringing. A second FET 202 may form a current mirror with the first FET 201, and a third FET 203 and a fourth FET 204 may form another current mirror. The CANL signal may be a voltage signal output from the drain of the first FET 201 to the transconductance amplifier 105, as explained below.

[0018] Figure 3 It shows according to Figure 1The circuit diagram 300 for the CANH driver 102 contains several components, some of which will not be discussed in detail here to avoid obscuring other aspects of the circuit. Figure 3 As shown, the CANH driver 102 may include a first FET 301, a second FET 302, a third FET 303, and a fourth FET 304. The first FET 301 and the third FET 303 may form a current mirror, wherein the first FET 301 is coupled to the second FET 302. The drain terminal of the second FET 302 may be coupled to the CANH line and may also receive an output current signal from the transconductance amplifier 105, as further explained below. Figure 3 An example circuit is shown for simulating ringing on a CAN bus, which can also be coupled to the drain terminal of a second FET 302.

[0019] Figure 4 It shows according to Figure 1 The circuit diagram 400 for the transconductance amplifier 105 contains several components, some of which will not be discussed in detail here to avoid obscuring other aspects of the circuit. Figure 4 As shown, the transconductance amplifier 105 may include a first FET 401 to receive a voltage signal from the CANL line at its gate terminal. The transconductance amplifier 105 may also include a second FET 402 to receive a CAN control signal at its gate terminal from processing circuitry (not shown) for generating the CAN control signal 101. For example, the processing circuitry for generating the CAN control signal 101 may generate a signal corresponding to an exponential function (e.g., e^(-1 / 2)). x The ratio of a first current signal to a second current signal corresponding to a hyperbolic function (e.g., cosh(x)) is the current signal corresponding to the ratio of the first current signal to the second current signal corresponding to a hyperbolic function (e.g., cosh(x)), where x is the input voltage supplied to the CAN bus. For example, the ratio corresponding to an exponential function (e.g., e^(-x)) is the ratio of the first current signal to the second current signal corresponding to the third current signal corresponding to the fourth current signal (e.g., e^(-x)). x The first current signal and the second current signal corresponding to the hyperbolic function (e.g., cosh(x)) can be generated by a transconducting linear loop circuit.

[0020] The transconductance amplifier 105 may include conversion circuitry, such as a diode-connected bipolar junction transistor (BJT), to convert the CAN control current signal into a corresponding voltage signal. The voltage signal corresponding to the CAN control current signal may be input to the gate terminal of a second FET 402, which, together with the first FET 401, forms the differential input of the transconductance amplifier 105. The transconductance amplifier 105 may include a third FET 403, a fourth FET 404, a fifth FET 405, and a sixth FET 406, which may receive a gain control signal and control the gain of the transconductance amplifier 105 based on the gain control signal.

[0021] Seventh FET 407, Eighth FET 408, Ninth FET 409, and Tenth FET 410 can form the output stage of transconductance amplifier 105 and can be coupled to fifth FET 405. Eleventh FET 411 and Twelfth FET 412 can be coupled to first FET 401, which can receive the CANL voltage signal. Thirteenth FET 413 and Fourteenth FET 414 can be coupled to second FET 402, which can receive the CAN control signal. Fifteenth FET 415 and Sixteenth FET 416 can be coupled to eleventh FET 411, twelfth FET 412, thirteenth FET 413, and fourteenth FET 414. Eighth FET 408 and Ninth FET 409 can output an output current signal to the CANH line based on the difference between the CAN control signal and the voltage signal from the CANL line. For example, the seventh FET 407 and the eighth FET 408 can be coupled to the voltage source VCC and can inject current into the CANH line based on the difference between the CAN control signal and the voltage signal from the CANL line. The ninth FET 409 and the tenth FET 410 can be coupled to ground or a common node and can therefore draw current from the CANH line based on the difference between the CAN control signal and the voltage signal from the CANL line. The injected or removed current can cancel out current oscillations between parasitic inductance and capacitance, thereby reducing ringing in the CAN bus.

[0022] Various examples have been disclosed herein in conjunction with the foregoing description and accompanying drawings. It should be understood that describing and illustrating each combination and sub-combination of these examples literally would be an undue repetition. Therefore, all examples can be combined in any manner or combination, and this specification (including the accompanying drawings) should be construed as constituting a complete written description of all combinations and sub-combinations of the examples described herein, as well as the ways and processes of preparing and using them, and should support the claims for any such combinations or sub-combinations.

[0023] Those skilled in the art will understand that the examples described herein are not limited to those specifically shown and described above. Furthermore, unless the contrary is mentioned above, it should be noted that all figures are not drawn to scale. Various modifications and variations are possible in accordance with the above teachings.

Claims

1. A circuit for suppressing ringing in a Controller Area Network (CAN) bus, the CAN bus having a CAN high (CANH) line and a CAN low (CANL) line, the circuit comprising: Processing circuitry, the processing circuitry being used to generate CAN control signals; and A transconductance amplifier is configured to receive a first input signal corresponding to the CAN control signal and a voltage signal from the CANL line, and to generate an output current signal based on the difference between the first input signal and the voltage signal from the CANL line. The output terminal of the transconductance amplifier is coupled to the CANH line to supply current to or draw current from the CANH line.

2. The circuit according to claim 1 further includes: A CAN low driver, the CAN low driver being coupled to the processing circuitry, ground or common node and the CANL line of the CAN bus; A CAN high driver, the CAN high driver being coupled to the processing circuit, the power supply voltage, and the CANH line of the CAN bus; and A terminating resistor is coupled between the CANH line and the CANL line of the CAN bus.

3. The circuit of claim 2, wherein the CAN low driver is coupled to the circuit simulating CAN bus ringing via the CANL line of the CAN bus, and the CAN high driver is coupled to the circuit simulating CAN bus ringing via the CANH line of the CAN bus.

4. The circuit of claim 1, wherein the transconductance amplifier is configured to receive a gain control signal to control the gain of the transconductance amplifier; and The output current signal is generated based on the gain control signal.

5. The circuit according to claim 4, wherein the gain control signal corresponds to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function.

6. The circuit according to claim 5, wherein the exponential function is e x Furthermore, the hyperbolic function is cosh(x), where x is the input voltage of the CAN bus.

7. The circuit according to claim 4, wherein the gain control signal is equivalent to the CAN control signal.

8. The circuit according to claim 1, further comprising: A conversion circuit, wherein the conversion circuit is used to convert a current signal into a voltage signal; The CAN control signal is a current signal corresponding to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function; and The conversion circuit is used to convert the CAN control signal into a voltage signal, which is then input to the transconductance amplifier as the first input signal.

9. The circuit according to claim 8, wherein the exponential function is e x And the hyperbolic function is cosh(x), where x is the input voltage to the CAN bus.

10. A method for suppressing ringing in a Controller Area Network (CAN) bus, the CAN bus having a CAN high (CANH) line and a CAN low (CANL) line, the method comprising: Generate CAN control signals; Receives a first input signal corresponding to the CAN control signal and a voltage signal from the CANL line; An output current signal is generated based on the difference between the first input signal and the voltage signal from the CANL line; as well as The current is supplied to the CANH line or drawn from the CANH line based on the output current signal.

11. The method of claim 10, further comprising: Receive gain control signal; The output current signal is generated based on the gain control signal.

12. The method of claim 11, wherein the gain control signal corresponds to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function.

13. The method of claim 12, wherein the exponential function is e x Furthermore, the hyperbolic function is cosh(x), where x is the input voltage of the CAN bus.

14. The method of claim 11, wherein the gain control signal is equivalent to the CAN control signal.

15. The method of claim 10, wherein the CAN control signal is a current signal corresponding to the ratio of a first current signal corresponding to an exponential function and a second current signal corresponding to a hyperbolic function; and The method includes converting the CAN control signal into a voltage signal received as the first input signal.

16. The method of claim 15, wherein the exponential function is e x Furthermore, the hyperbolic function is cosh(x), where x is the input voltage of the CAN bus.

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