A circuit system capable of increasing the noise margin of CAN bus signals

Abstract

The invention provides a circuit system capable of increasing the noise margin of CAN bus signals. The circuit system comprises a CAN bus transceiver. The CAN bus transceiver comprises a CAN bus high end, a CAN bus low end, a power source end and a power source ground end, wherein the power source end and the power source ground end are connected to a positive electrode and a power source ground of a power supply source. The circuit system also comprises a positive power source with the power source ground as the central ground, a negative power source, a first constant current source and a second constant current source. By means of the functions of the constant current source CC1 and the constant current source CC2, when the CAN transceiver outputs a high differential voltage, the voltage value is higher than a voltage value in the prior art, and when the CAN transceiver outputs a low differential voltage, the voltage of the CANL end is higher than that of the CANH end, so that differential negative voltage output is realized. Therefore, the output voltage identification threshold is effectively increased, namely the noise margin is raised; further the anti-interference capability of a twisted-pair type CAN communication bus is improved and the CAN communication bus can be applied in an environment with great electromagnetic interference.

Description

Technical field [0001] The present invention relates to an interface circuit for CAN communication, in particular to a circuit for improving the noise tolerance of CAN bus signals. Background technique [0002] ControllerAreaNetwork is abbreviated as CAN, and its full name is Controller Area Network, which has become the serial communication protocol standard of ISO (International Organization for Standardization). CAN bus communication has good ease of use, network security, communication reliability and real-time performance, so it is widely used in fields such as automobiles, ships, medical and industrial control equipment. [0003] Usually, CAN transceiver (such as SN65HVD251, PCA82C250, etc.) converts the logic level output from the CAN controller into a differential signal to complete the sending and receiving of messages. The purpose is to extend the communication distance and enhance the anti-interference ability. Twisted pair cable (or ordinary parallel cable) has the cha...

AI Technical Summary

Problems solved by technology

However, the use of optical fiber significantly increases the application cost of CAN, which brings inconvenience to the increase in the number of nodes (in the optical fiber solution, adding a node requires additional optical fiber receiving components, sending components, and a CAN transceiver, which is far less than twisted pair It is so convenient to connect the bus in parallel to complete the node increase), which weakens the ease of use of CAN

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