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TCAN1051HGV: ACK ERROR

GARETH OU
Guru 10365 points
Part Number: TCAN1051HGV
Other Parts Discussed in Thread: TCAN1051

Hi 

Customers use 20 meters cable at 1MHZ,

2 NODE test OK

5 NODE found abnormality ACK ERROR waveform is as follows

Yellow is TX

Blue is RX

Red is CANH

Green is CANL

Is it a product problem?

  • 0
    TI__Mastermind 19930 points

    Hi Gareth,

    It looks like there was signal integrity issue due to the ringing on the bus, and thus caused the glitch on RXD to receive an error bit. This kind of communication errors in systems can by caused with higher data rates, large physical bus topologies, etc. Did the customer put common mode choke and terminate bus properly? 

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Guru 10365 points

    Hi Sean

    1.Could you help check the below TCAN1051 schematic and any need to adjust

    2.Where is the recommended common mode choke to be added? Should it be added to every NODE?

  • 0 in reply to GARETH OU
    TI__Mastermind 19930 points

    Hi Gareth,

    Looks like they are not using CMC so placing it between transceiver CANH/L pins and the termination resistance would be helpful to reduce the ringings.

    The image is not clear, what are those two resistors on the bus? Terminations or series resistance? Or just DNP?

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Guru 10365 points

    Hi Sean

    The schematic is updated as follows

  • 0 in reply to GARETH OU
    TI__Mastermind 19930 points

    Hi Gareth,

    The schematic looks fine, but we still recommend to use common mode choke to solve that ringing issue on the bus (which caused the ACK error). CMC can be placed somewhere like below:

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Guru 10365 points

    Hi  Sean

    The Differential input capacitance of competitive product NCV7351 is smaller than that of TCAN1051. Will this affect the transmission quality?

  • 0 in reply to GARETH OU
    TI__Guru 51025 points

    Hi Gareth, 

    There are many transceiver factors that impact ringing, most of which are bus driver characteristics. These include paracitics such as capacitance as well as driver behavior such as ringing suppression technique, timing, and drive strength. Typically these are very similar between similarly specified transceivers, so the main way to improve signal quality will be to simplify or modify the bus harness or change to a different class of transceiver (such as a CAN SIC device for improved ringing suppression). 

    In this case it looks like the addition of a common mode choke would help improve the signal quality in them system. I've linked an application note below that goes over some of the details of CMCs and includes various part numbers that may be suitable for your application. 
    https://www.ti.com/lit/an/slla271/slla271.pdf?ts=1676993696425&ref_url=https%253A%252F%252Fwww.google.com%252F 

    Regards, 
    Eric Schott