How should a failure in the CAN communication surge test be handled?

If a CAN communication surge test fails, one should inspect the TVS selection, CANH/CANL protection scheme, common-mode choke parameters, termination resistor placement, transceiver voltage withstand capability, and PCB grounding paths. Surge test failures may manifest as communication interruptions, transceiver damage, system resets, or functional anomalies (such as issues with the recessive state) following the test.

I. First, identify the type of failure

If the CAN transceiver is damaged following a surge, focus on inspecting the TVS clamping capability and the energy dissipation path; if the issue is merely a communication interruption, check for common-mode interference, ground bounce, and system resets; if the failure is intermittent, pay attention to the consistency of the test path.

CAN buses typically connect to the external environment via wiring harnesses, and surge energy can enter the system through CANH, CANL, or the ground line.

II. Key Inspection Points

Check whether the TVS operating voltage is suitable for the CAN bus; whether the clamping voltage is below the transceiver's tolerance limit; whether the TVS is placed close to the interface; whether the common-mode choke saturates or affects the waveform; whether the termination resistor is reasonably laid out; and whether the ground path is short and continuous.

For CAN FD applications, it is also necessary to verify whether device parasitic capacitance and common-mode choke impedance affect high-speed communication.

III. Remediation Measures

Replace the CAN-specific TVS with one of the appropriate voltage and power ratings; optimize the TVS grounding; adjust the position or specifications of the common-mode choke; optimize terminal matching; and separate the surge discharge path from the sensitive signal path.

Upon completion of the remediation, verify surge immunity, ESD immunity, communication error rates, signal waveforms, and long-term operational stability.

IV. Asaim Support

Asaim provides TVS, common-mode chokes, and EMC rectification solutions for automotive CAN, industrial CAN, and CAN FD interfaces, assisting customers with troubleshooting during testing and verifying component replacements.

FAQs

Q: Does a CAN surge failure necessarily indicate insufficient TVS power rating?

A: Not necessarily; it could also be caused by excessive clamping voltage, a poor grounding path, or common-mode interference.

Q: Do both CANH and CANL require protection?

A: Typically, symmetrical protection for both lines is required to prevent differential signal imbalance.

Q: Is it more difficult to resolve issues with CAN FD compared to standard CAN?

A: Generally, yes; CAN FD is more sensitive because its higher data rate makes it more susceptible to the effects of parasitic parameters and waveform distortion.