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TCAN1042HGV-Q1: CAN TVS and application questions

Part Number: TCAN1042HGV-Q1
Other Parts Discussed in Thread: TCAN1043, TCAN1043-Q1

Hi Team,

My customer now use TCAN1042 and meet some question. Could you please kindly help for these?

  • Whether this connection can realize the CAN communication on the board and also communicate with the outside the board at the same time.

  • Does TI have TVS recommendation spec or part number in CAN H and CAN L?
  • May I ask how much the TVS parasitic capacitance matched on CANFD cannot be higher than?
  • How much capacitance to ground can not be exceeded on CANFD?

  • Amelie,

    This connection scheme will work, but it seems like it's a redundant setup, I'm assuming that's the intention because both MCU and CPU will be receiving the same data back from the CAN bus. Will the MCU and CPU be sending the same data on TXD as well?

    A common TVS diode used in CAN systems is the PESD1CAN device. These are used in many CAN systems on the CAN bus to protect from ESD and other voltage transient events.

    The amount of bus capacitance will depend on the amount of nodes on the bus, and the highest data rate being used. More capacitance will lead to slower rise and fall times in the CAN bus waveforms, which will lead to longer delays between TXD and RXD. This can lead to bit errors in the controller since it needs to transmit and read the bus within the same bit time to make sure the bus is reflecting what it is transmitting. We ran some studies on bus capacitive loading in our lab on the TCAN1042 up to 10Mbps. A clock signal at different data rates is sent through, and waveforms were captured on CANH, CANL, TXD, and RXD, with 1nF and 2nF levels of capacitance.

    At 2Mbps, a significant delay between TXD and RXD is seen at 2nF overall bus capacitance. At 4Mbps, 1nF overall bus capacitance is showing significant delay, and 2nF alters the RXD waveform enough to make it very difficult for the controller to read the data back on RXD. And as the data rates get higher they are more susceptible to less capacitance causing significant waveform distortion. 

    If you email me directly I can send over the presentation that has the waveform captures from this test.

    Please let me know if you have any other questions.

    Regards,

  • Is it too small for us to use a 10pF capacitor on canfd?

  • User,

    No, 10pF can be used on the CAN bus pins for a CANFD node. 

    If you have any other questions, feel free to start another thread. Since the original poster's question was addressed, I'm closing this thread.

    Regards,

  • Does your company’s 1043 CAN chip and NXP’s software and hardware are compatible?

  • User,

    Yes, they are compatible, the only different is the missing SPLIT pin at pin 11 on the TCAN1043. The SPLIT pin is meant to stabilize the common-mode signal to help with RF emissions from the CAN transceiver. In the TCAN series of devices, it was proven that RF emissions certifications for the automotive market could be passed without the need for a SPLIT pin, so it was not included on the TCAN1042 nor the TCAN1043.

    If you email me directly, I can send over a document that explains any timing differences between TCAN1043-Q1 and its competitors that will help with any misunderstandings in the software side of the application. You can find my email by clicking on my username.

    Regards,

  • OK,TKS,My email is zhangcheng@maxieyetech.com

    My wechat is cococo_hk

  • User,

    Okay, I sent over an email. Let's keep the conversation in email for now.

    Regards,