CAN bus output driver circuit

Abstract

The present invention discloses a CAN bus output drive circuit, comprising: a first switching circuit and a second switching circuit. The first switching circuit is connected to the first output terminal, and the first switching circuit comprises a first MOS tube and a first switch tube; the second switching circuit is connected to the second output terminal, and the second switching circuit comprises a second MOS tube and a second switch tube; when the first MOS tube and the second MOS tube are in the on or off state, a dominant or recessive level signal is output; the first switch tube and / or the second switch tube works in a switch state. According to the CAN bus output drive circuit of the present invention, by replacing the original high-voltage diode with a high-voltage device working in a switch state, and controlling the working state of the two high-voltage switch tubes by a control signal, the cost of the CAN bus output drive circuit is reduced, and the reliability indicators of the circuit such as ESD and Latch‑up are greatly improved, thereby improving the stability and reliability of the circuit operation.

Description

Technical Field

[0001] The invention relates to the field of integrated circuits, in particular to a CAN bus output drive circuit. Background Art

[0002] CAN (Controller Area Network) bus was developed by BOSCH of Germany and became an international standard (ISO11898). Due to its high reliability and good error detection capabilities, it has been widely used in the automotive and industrial control fields.

[0003] Figure 1 It is a commonly used CAN bus output drive circuit, which outputs dominant level signal or recessive level signal by controlling the on and off of MOS tube P1 and MOS tube N1. High voltage diode D1 is used to prevent the negative voltage on the CAN bus from flowing back to GND, and high voltage diode D2 is used to prevent the positive voltage on the CAN bus from flowing back to the power supply VCC.

[0004] The above circuit has the following two problems:

[0005] 1. The on-resistance of high-voltage diodes D1 and D2 is usually large. To achieve the performance specified in the ISO11898 standard, a larger area is required, which will significantly increase the chip cost.

[0006] 2. Whether it is a high-voltage CMOS process, a high-voltage BIPOLAR process or a high-voltage BCD process, high-voltage diode devices are usually accompanied by the presence of parasitic PNP and parasitic NPN. These parasitic devices are often triggered when a large current flows through the high-voltage diode, seriously affecting the normal performance of the circuit. At the same time, the presence of parasitic devices will also have a relatively large impact on the ESD and latch-up performance of the circuit, greatly reducing the reliability of the circuit.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] The object of the present invention is to provide a CAN bus output drive circuit, which can reduce chip costs while improving circuit stability and reliability.

[0009] To achieve the above objective, an embodiment of the present invention provides a CAN bus output drive circuit, comprising: a first switching circuit, a second switching circuit and a clamping circuit.

[0010] The first switching circuit is connected to the first power supply voltage and the first output terminal. The first switching circuit includes a first MOS tube and a first switch tube connected in series. The positive voltage on the CAN bus is prevented from flowing back to the first power supply voltage by turning off the first switch tube.

[0011] The second switching circuit is connected to the ground voltage and the second output terminal. The second switching circuit includes a second MOS tube and a second switch tube connected in series. The negative voltage on the CAN bus is prevented from flowing back to the ground voltage by turning off the second switch tube.

[0012] The clamping circuit is used to clamp the differential voltage of the CAN bus.

[0013] The first MOS transistor and the second MOS transistor are turned on and off under the control of a driving signal. When the first MOS transistor and the second MOS transistor are in the turned-on or turned-off state, the first output terminal and the second output terminal output a dominant level or a recessive level.

[0014] The first switch tube and / or the second switch tube operates in a switching state and is turned on and off under the control of a control signal.

[0015] In one or more embodiments of the present invention, the driving circuit also includes a logic control circuit, which is connected to the first switch tube and / or the second switch tube to output a logic control signal to control the conduction and shutdown of the first switch tube and / or the second switch tube.

[0016] In one or more embodiments of the present invention, the first end of the clamp circuit is connected to the first MOS transistor and the first switch transistor or to the first output end, and the second end is connected to the second MOS transistor and the second switch transistor or to the second output end.

[0017] In one or more embodiments of the present invention, the clamping circuit includes a third MOS tube and a fourth MOS tube, the source of the third MOS tube forms a first end of the clamping circuit, the drain of the fourth MOS tube forms a second end of the clamping circuit, and the drain of the third MOS tube is connected to the source of the fourth MOS tube and is also connected to the gates of the third MOS tube and the fourth MOS tube.

[0018] In one or more embodiments of the present invention, the driving circuit also includes a first resistor and a second resistor, the first end of the first resistor is connected to the first output end, the second end of the second resistor is connected to the second output end, and the second end of the first resistor is connected to the first end of the second resistor and is also connected to the second power supply voltage.

[0019] In one or more embodiments of the present invention, the first switch tube and the second switch tube are both MOS tubes;

[0020] The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive the control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the drive signal, and the source of the second MOS tube is connected to the ground voltage; or

[0021] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a driving signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive a control signal, and the drain of the second switch tube is connected to the ground voltage; or

[0022] The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive the control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive the drive signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive the control signal, and the drain of the second switch tube is connected to the ground voltage; or

[0023] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive a control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive a driving signal, and the source of the second MOS tube is connected to the ground voltage.

[0024] In one or more embodiments of the present invention, the first switch tube is a MOS tube, and the second switch tube is a diode;

[0025] The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive a control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive a drive signal, and the drain of the first MOS tube is connected to the first output end; the anode of the second switch tube is connected to the second output end, the cathode of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive a drive signal, and the source of the second MOS tube is connected to the ground voltage; or

[0026] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a driving signal, the source of the second MOS tube is connected to the anode of the second switch tube, and the cathode of the second switch tube is connected to the ground voltage; or

[0027] The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive a control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive a drive signal, and the drain of the first MOS tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a drive signal, the source of the second MOS tube is connected to the anode of the second switch tube, and the cathode of the second switch tube is connected to the ground voltage; or

[0028] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the anode of the second switch tube is connected to the second output end, the cathode of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the driving signal, and the source of the second MOS tube is connected to the ground voltage.

[0029] In one or more embodiments of the present invention, the first switch tube is a diode, and the second switch tube is a MOS tube;

[0030] The anode of the first switch tube is connected to the first power supply voltage, the cathode of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output terminal; the source of the second switch tube is connected to the second output terminal, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the drive signal, and the source of the second MOS tube is connected to the ground voltage; or

[0031] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive the driving signal, the drain of the first MOS tube is connected to the anode of the first switch tube, and the cathode of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive the driving signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive the control signal, and the drain of the second switch tube is connected to the ground voltage; or

[0032] The anode of the first switch tube is connected to the first power supply voltage, the cathode of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output terminal; the drain of the second MOS tube is connected to the second output terminal, the gate of the second MOS tube is used to receive the drive signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive the control signal, and the drain of the second switch tube is connected to the ground voltage; or

[0033] The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive the driving signal, the drain of the first MOS tube is connected to the anode of the first switch tube, and the cathode of the first switch tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the driving signal, and the source of the second MOS tube is connected to the ground voltage.

[0034] In one or more embodiments of the present invention, both the first switch tube and the second switch tube are high-voltage devices.

[0035] In one or more embodiments of the present invention, the clamping circuit is composed of high-voltage devices and / or low-voltage devices.

[0036] Compared with the prior art, the CAN bus output drive circuit according to the embodiment of the present invention prevents backflow of the CAN bus by replacing the original high-voltage diode with a high-voltage device (a first switch tube and a second switch tube) working in a switching state (linear region), and controlling the working state of the two high-voltage switch tubes through a control signal; the use of the first switch tube and the second switch tube reduces the influence of parasitic PNP and NPN associated with the high-voltage diode device, reduces the cost of the CAN bus output drive circuit, and greatly improves the reliability indicators of the circuit such as ESD and Latch-up, thereby improving the stability and reliability of the circuit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a circuit schematic diagram of a CAN bus output drive circuit in the prior art.

[0038] Figure 2 4 is a circuit schematic diagram of a CAN bus output drive circuit according to Embodiment 1 of the present invention.

[0039] Figure 3 4 is another circuit schematic diagram of the CAN bus output drive circuit according to the first embodiment of the present invention.

[0040] Figure 4 4 is a circuit schematic diagram of a CAN bus output drive circuit according to the second embodiment of the present invention.

[0041] Figure 5 4 is a circuit schematic diagram of a CAN bus output drive circuit according to Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0042] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0043] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0044] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuit, a programmable circuit, a state machine circuit and / or an element that can store instructions executed by a programmable circuit. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0045] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0046] Embodiment 1:

[0047] like Figure 2 As shown, a CAN bus output drive circuit includes: a first switching circuit 10, a second switching circuit 20, a logic control circuit 30, a clamping circuit 40, a first resistor R1 and a second resistor R2.

[0048] The first switching circuit 10 is connected to the first power supply voltage VCC1 and the first output terminal CANH. The first switching circuit 10 includes a first MOS tube P1 and a first switch tube P2 connected in series. The positive voltage on the CAN bus is prevented from flowing back to the first power supply voltage VCC1 by turning off the first switch tube P2.

[0049] The second switching circuit 20 is connected to the ground voltage GND and the second output terminal CANL. The second switching circuit 20 includes a second MOS tube N1 and a second switch tube N2 connected in series. The negative voltage on the CAN bus is prevented from flowing back to the ground voltage GND by turning off the second switch tube N2.

[0050] The first MOS transistor P1 and the second MOS transistor N1 are turned on and off under the control of the driving signal. When the first MOS transistor P1 and the second MOS transistor N1 are in the turned-on or turned-off state, the first output terminal CANH and the second output terminal CANL output a dominant level or a recessive level.

[0051] In this embodiment, the first switch tube P2 and the second switch tube N2 are both high-voltage devices, that is, they can be high-voltage CMOS devices, high-voltage BIPOLAR devices or high-voltage BCD devices.

[0052] The logic control circuit 30 is connected to the first switch tube P2 and the second switch tube N2 to output a logic control signal to control the first switch tube P2 and the second switch tube N2. The first switch tube P2 and the second switch tube N2 work in a switching state (linear region) and are turned on and off under the control of the logic control signal.

[0053] In other embodiments, the logic control circuit 30 may be selectively connected to the first switch tube P2 or the second switch tube N2.

[0054] The clamp circuit 40 has a first end connected to the first MOS transistor P1 and the first switch transistor P2 or to the first output terminal CANH, and a second end connected to the second MOS transistor N1 and the second switch transistor N2 or to the second output terminal CANL.

[0055] like Figure 3As shown, the clamping circuit 40 includes a third MOS transistor P3 and a fourth MOS transistor N3, and the number of the third MOS transistor P3 and the fourth MOS transistor N3 is not specifically limited. The source of the third MOS transistor P3 forms the first end of the clamping circuit 40, and the drain of the fourth MOS transistor N3 forms the second end of the clamping circuit 40. The drain of the third MOS transistor P3 is connected to the source of the fourth MOS transistor N3 and is also connected to the gates of the third MOS transistor P3 and the fourth MOS transistor N3. In other embodiments, the clamping circuit 40 may be composed of other devices.

[0056] When the differential voltage between the first output terminal CANH and the second output terminal CANL is too high, the clamp circuit 40 is turned on to clamp the first output terminal CANH and the second output terminal CANL, which can meet the requirement of ISO11898 standard that the differential voltage is less than 5V when the CAN bus is unloaded or the load resistance is greater than 2.4KΩ.

[0057] The clamp circuit 40 is composed of high voltage devices and / or low voltage devices. That is, the third MOS transistor P3 and / or the fourth MOS transistor N3 are high voltage devices or low voltage devices. The high voltage devices may be high voltage CMOS devices, high voltage BIPOLAR devices, or high voltage BCD devices.

[0058] The first end of the first resistor R1 is connected to the first output terminal CANH, and the second end of the second resistor R2 is connected to the second output terminal CANL. The second end of the first resistor R1 is connected to the first end of the second resistor R2 and the second power supply voltage VCC2. The voltage value of the second power supply voltage VCC2 is half of the voltage value of the first power supply voltage VCC1.

[0059] In this embodiment, the first switch transistor P2 and the second switch transistor N2 are both MOS transistors and are N-channel MOS transistors. In other embodiments, the first switch transistor P2 and the second switch transistor N2 can be P-channel MOS transistors. Since the first switch transistor P2 and the second switch transistor N2 both work in the switching state (linear region), the current flowing through them all passes through the channel, and the current conduction capability is greatly improved. Compared with the traditional high-voltage diodes D1 and D2, the device area is greatly reduced.

[0060] In addition, since the first switch tube P2 and the second switch tube N2 operate in the linear region, under the same conduction current condition, the voltage between the drain and the source of the first switch tube P2 and the second switch tube N2 is very small, which greatly reduces the conditions for parasitic NPN or PNP triggering and greatly enhances the stability and reliability of the circuit operation.

[0061] like Figure 2 and Figure 3As shown, the drain of the first switch tube P2 is connected to the first power supply voltage VCC1, the gate of the first switch tube P2 is used to receive the control signal, the source of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the drive signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the source of the second switch tube N2 is connected to the second output terminal CANL, the gate of the second switch tube N2 is used to receive the control signal, the drain of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the drive signal, and the source of the second MOS tube N1 is connected to the ground voltage GND. The first end of the clamp circuit 40 is connected to the source of the first MOS tube P1 and the first switch tube P2 or to the first output terminal CANH, and the second end is connected to the drain of the second MOS tube N1 and the second switch tube N2 or to the second output terminal CANL.

[0062] In other embodiments, based on the present embodiment, the connection sequence of the first switch tube P2 and the first MOS tube P1 can be exchanged, and the connection sequence of the second switch tube N2 and the second MOS tube N1 can also be exchanged. That is, the source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the drive signal, the drain of the first MOS tube P1 is connected to the drain of the first switch tube P2, the gate of the first switch tube P2 is used to receive the control signal, and the source of the first switch tube P2 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the drive signal, the source of the second MOS tube N1 is connected to the source of the second switch tube N2, the gate of the second switch tube N2 is used to receive the control signal, and the drain of the second switch tube N2 is connected to the ground voltage GND.

[0063] In other embodiments, based on the present embodiment, only the connection sequence of the second switch tube N2 and the second MOS tube N1 is exchanged. The drain of the first switch tube P2 is connected to the first power supply voltage VCC1, the gate of the first switch tube P2 is used to receive the control signal, the source of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the drive signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the drive signal, the source of the second MOS tube N1 is connected to the source of the second switch tube N2, the gate of the second switch tube N2 is used to receive the control signal, and the drain of the second switch tube N2 is connected to the ground voltage GND; or

[0064] In other embodiments, based on the present embodiment, only the connection sequence of the first switch tube P2 and the first MOS tube P1 is exchanged. The source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the drive signal, the drain of the first MOS tube P1 is connected to the drain of the first switch tube P2, the gate of the first switch tube P2 is used to receive the control signal, and the source of the first switch tube P2 is connected to the first output terminal CANH; the source of the second switch tube N2 is connected to the second output terminal CANL, the gate of the second switch tube N2 is used to receive the control signal, the drain of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the drive signal, and the source of the second MOS tube N1 is connected to the ground voltage GND.

[0065] Embodiment 2:

[0066] The difference between this embodiment and the first embodiment is that the first switch tube P2 is a MOS tube, the second switch tube N2 is a diode, and both the MOS tube and the diode are high-voltage tubes.

[0067] like Figure 4 As shown, the drain of the first switch tube P2 is connected to the first power supply voltage VCC1, the gate of the first switch tube P2 is used to receive the control signal, the source of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the drive signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the anode of the second switch tube N2 is connected to the second output terminal CANL, the cathode of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the drive signal, and the source of the second MOS tube N1 is connected to the ground voltage GND.

[0068] In other embodiments, the connection sequence of the first switch tube P2 and the first MOS tube P1 and the connection sequence of the second switch tube N2 and the second MOS tube N1 are exchanged on the basis of the present embodiment. That is, the source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the driving signal, the drain of the first MOS tube P1 is connected to the drain of the first switch tube P2, the gate of the first switch tube P2 is used to receive the control signal, the source of the first switch tube P2 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the driving signal, the source of the second MOS tube N1 is connected to the anode of the second switch tube N2, and the cathode of the second switch tube N2 is connected to the ground voltage GND.

[0069] In other embodiments, based on the present embodiment, only the connection sequence of the second switch tube N2 and the second MOS tube N1 is exchanged. That is, the drain of the first switch tube P2 is connected to the first power supply voltage VCC1, the gate of the first switch tube P2 is used to receive the control signal, the source of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the drive signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the drive signal, the source of the second MOS tube N1 is connected to the anode of the second switch tube N2, and the cathode of the second switch tube N2 is connected to the ground voltage GND.

[0070] In other embodiments, based on the present embodiment, only the connection sequence of the first switch tube P2 and the first MOS tube P1 is exchanged. The source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the drive signal, the drain of the first MOS tube P1 is connected to the drain of the first switch tube P2, the gate of the first switch tube P2 is used to receive the control signal, and the source of the first switch tube P2 is connected to the first output terminal CANH; the anode of the second switch tube N2 is connected to the second output terminal CANL, the cathode of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the drive signal, and the source of the second MOS tube N1 is connected to the ground voltage GND.

[0071] Embodiment 3:

[0072] The difference between this embodiment and the first embodiment is that the first switch tube P2 is a diode, the second switch tube N2 is a MOS tube, and both the MOS tube and the diode are high-voltage tubes.

[0073] like Figure 5 As shown, the anode of the first switch tube P2 is connected to the first power supply voltage VCC1, the cathode of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the driving signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the source of the second switch tube N2 is connected to the second output terminal CANL, the gate of the second switch tube N2 is used to receive the control signal, the drain of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the driving signal, and the source of the second MOS tube N1 is connected to the ground voltage GND.

[0074] In other embodiments, on the basis of the present embodiment, the connection sequence of the first switch tube P2 and the first MOS tube P1 and the connection sequence of the second switch tube N2 and the second MOS tube N1 are exchanged. That is, the source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the drive signal, the drain of the first MOS tube P1 is connected to the anode of the first switch tube P2, and the cathode of the first switch tube P2 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the drive signal, the source of the second MOS tube N1 is connected to the source of the second switch tube N2, the gate of the second switch tube N2 is used to receive the control signal, and the drain of the second switch tube N2 is connected to the ground voltage GND.

[0075] In other embodiments, based on the present embodiment, only the connection sequence of the second switch tube N2 and the second MOS tube N1 is exchanged. The anode of the first switch tube P2 is connected to the first power supply voltage VCC1, the cathode of the first switch tube P2 is connected to the source of the first MOS tube P1, the gate of the first MOS tube P1 is used to receive the drive signal, and the drain of the first MOS tube P1 is connected to the first output terminal CANH; the drain of the second MOS tube N1 is connected to the second output terminal CANL, the gate of the second MOS tube N1 is used to receive the drive signal, the source of the second MOS tube N1 is connected to the source of the second switch tube N2, the gate of the second switch tube N2 is used to receive the control signal, and the drain of the second switch tube N2 is connected to the ground voltage GND.

[0076] In other embodiments, based on the present embodiment, only the connection sequence of the first switch tube P2 and the first MOS tube P1 is exchanged. That is, the source of the first MOS tube P1 is connected to the first power supply voltage VCC1, the gate of the first MOS tube P1 is used to receive the drive signal, the drain of the first MOS tube P1 is connected to the anode of the first switch tube P2, and the cathode of the first switch tube P2 is connected to the first output terminal CANH; the source of the second switch tube N2 is connected to the second output terminal CANL, the gate of the second switch tube N2 is used to receive the control signal, the drain of the second switch tube N2 is connected to the drain of the second MOS tube N1, the gate of the second MOS tube N1 is used to receive the drive signal, and the source of the second MOS tube N1 is connected to the ground voltage GND.

[0077] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A CAN bus output drive circuit, characterized in that: include: A first switching circuit is connected to the first power supply voltage and the first output end, wherein the first switching circuit comprises a first MOS tube and a first switch tube connected in series between the first power supply voltage and the first output end, and the positive voltage on the CAN bus is prevented from flowing back to the first power supply voltage by turning off the first switch tube; A second switching circuit is connected to the ground voltage and the second output terminal, wherein the second switching circuit includes a second MOS tube and a second switch tube connected in series between the ground voltage and the second output terminal, and the negative voltage on the CAN bus is prevented from flowing back to the ground voltage by turning off the second switch tube; as well as A clamping circuit, used for clamping the differential voltage of a CAN bus; a first end of the clamping circuit is connected to a node between a first MOS tube and a first switch tube, and a second end is connected to a node between a second MOS tube and a second switch tube; the clamping circuit comprises a third MOS tube and a fourth MOS tube, a source of the third MOS tube forms a first end of the clamping circuit, a drain of the fourth MOS tube forms a second end of the clamping circuit, and the drain of the third MOS tube is connected to a source of the fourth MOS tube and is simultaneously connected to the gates of the third MOS tube and the fourth MOS tube; The first MOS transistor and the second MOS transistor are turned on and off under the control of the driving signal, and when the first MOS transistor and the second MOS transistor are in the turned-on or turned-off state, the first output terminal and the second output terminal output a dominant level signal or a recessive level signal; The first switch tube and / or the second switch tube works in a switch state and is turned on and off under the control of a control signal. The first switch tube and / or the second switch tube is a MOS tube. The first switch tube and the second switch tube are both high-voltage devices.

2. The CAN bus output drive circuit according to claim 1, characterized in that: The driving circuit also includes a logic control circuit, which is connected to the first switch tube and / or the second switch tube to output a logic control signal to control the on and off of the first switch tube and / or the second switch tube.

3. The CAN bus output drive circuit according to claim 1, characterized in that: The driving circuit also includes a first resistor and a second resistor, wherein the first end of the first resistor is connected to the first output end, the second end of the second resistor is connected to the second output end, and the second end of the first resistor is connected to the first end of the second resistor and is also connected to a second power supply voltage.

4. The CAN bus output drive circuit according to claim 1, characterized in that: The first switch tube and the second switch tube are both MOS tubes; The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive the control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the drive signal, and the source of the second MOS tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a driving signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive a control signal, and the drain of the second switch tube is connected to the ground voltage; or The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive the control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive the drive signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive the control signal, and the drain of the second switch tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive a control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive a driving signal, and the source of the second MOS tube is connected to the ground voltage.

5. The CAN bus output drive circuit according to claim 1, characterized in that: The first switch tube is a MOS tube, and the second switch tube is a diode; The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive a control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive a drive signal, and the drain of the first MOS tube is connected to the first output end; the anode of the second switch tube is connected to the second output end, the cathode of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive a drive signal, and the source of the second MOS tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a driving signal, the source of the second MOS tube is connected to the anode of the second switch tube, and the cathode of the second switch tube is connected to the ground voltage; or The drain of the first switch tube is connected to the first power supply voltage, the gate of the first switch tube is used to receive a control signal, the source of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive a drive signal, and the drain of the first MOS tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a drive signal, the source of the second MOS tube is connected to the anode of the second switch tube, and the cathode of the second switch tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the drain of the first switch tube, the gate of the first switch tube is used to receive a control signal, and the source of the first switch tube is connected to the first output end; the anode of the second switch tube is connected to the second output end, the cathode of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the driving signal, and the source of the second MOS tube is connected to the ground voltage.

6. The CAN bus output drive circuit according to claim 1, characterized in that: The first switch tube is a diode, and the second switch tube is a MOS tube; The anode of the first switch tube is connected to the first power supply voltage, the cathode of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output terminal; the source of the second switch tube is connected to the second output terminal, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the drive signal, and the source of the second MOS tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive a driving signal, the drain of the first MOS tube is connected to the anode of the first switch tube, and the cathode of the first switch tube is connected to the first output end; the drain of the second MOS tube is connected to the second output end, the gate of the second MOS tube is used to receive a driving signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive a control signal, and the drain of the second switch tube is connected to the ground voltage; or The anode of the first switch tube is connected to the first power supply voltage, the cathode of the first switch tube is connected to the source of the first MOS tube, the gate of the first MOS tube is used to receive the drive signal, and the drain of the first MOS tube is connected to the first output terminal; the drain of the second MOS tube is connected to the second output terminal, the gate of the second MOS tube is used to receive the drive signal, the source of the second MOS tube is connected to the source of the second switch tube, the gate of the second switch tube is used to receive the control signal, and the drain of the second switch tube is connected to the ground voltage; or The source of the first MOS tube is connected to the first power supply voltage, the gate of the first MOS tube is used to receive the driving signal, the drain of the first MOS tube is connected to the anode of the first switch tube, and the cathode of the first switch tube is connected to the first output end; the source of the second switch tube is connected to the second output end, the gate of the second switch tube is used to receive the control signal, the drain of the second switch tube is connected to the drain of the second MOS tube, the gate of the second MOS tube is used to receive the driving signal, and the source of the second MOS tube is connected to the ground voltage.

7. The CAN bus output drive circuit according to claim 1, characterized in that: The clamping circuit is composed of high-voltage devices and / or low-voltage devices.

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