Dear NXP Technical Team,
We have encountered an occasional issue where TJA1043T is unable to transmit or receive messages properly during use. Could you please confirm whether the following CAN bus environment might affect the normal operation of TJA1043T:
Source voltage: 13.72V
CAN_H voltage: 2.8V
CAN_L voltage: 2.2V
Thanks for your support.
Alex
Dear Tomas,
Thank you for your detailed response and insights.
As you suggested, we have captured the actual CAN bus waveforms during operation on the vehicle using the oscilloscope. Please refer to the attached screenshot for the waveform details.
Measurement points: CAN_H and CAN_L at the TJA1043 transceiver side
Could you please help us analyze the quality of the bus signals based on the waveform? Specifically, we would like to know:
(1) Whether there are any noticeable ringing, overshoot, or signal integrity issues.
(2)If the signal shape and level meet the requirements for reliable CAN communication.
(3)Whether any observed anomalies might contribute to occasional communication errors or error frames.
Your further guidance would be greatly appreciated.
Best regards,
Alex
Dear Alex,
If I understood correctly, the differential voltage between CAN_H and CAN_L in your setup is: V_diff = CAN_H - CAN_L = 2.8V - 2.2V = 0.6V
This value is below the typical threshold for a dominant state, which is usually between 1.5V and 3V in Normal mode (see datasheet Table 8). In recessive state, the bus voltages should be approximately equal and centered around 0.5 × VCC. So differential voltage of 0.6V may not be reliably interpreted as either dominant or recessive, potentially leading to communication errors.
To ensure proper operation:
- Confirm correct bus termination.
- Ensure consistent ground potential across all nodes.
- Verify that the transceiver is in Normal mode and not in Standby or Sleep mode.
- Check for any external biasing or leakage affecting the bus lines.
If the issue persists, capturing bus waveforms during failure events and monitoring the ERR_N pin for diagnostic flags may help identify the root cause.
BRs, Tomas