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SN65HVD231Q: Need help stuck with engineers stating current design is correct.

TERRY WADE
Prodigy 10 points
Part Number: SN65HVD231Q

The above circuit is located into two places.  One is in a cockpit of an aircraft as a controller with this CAN interface; the other is on a transmitter located about 30 feet past noisy generators and the like.  We brought the transmitters and the controller into a anechoic chamber to test RS106, and RS103.  During MIL-STD RS103 testing both SN65HVD231Q's transmitter and controller have been destroyed and had to be replaced.  This is repeatable;   I realize the resistors are being biased to ground by each leg of 60 ohms and your documentation just shows 120 ohms across the CANL and CANH - this was suggested by an instructor of long ago to reduce noise.   Our grounds could differ greatly because the controller was outside of the chamber.   Can you recommend a change that we may want to try?

The image looks muted as it was clear when I loaded it.

  • 0
    Guru 284590 points

    Split termination is commonly used with CAN, but then R21 would be a capacitor.

    CAN transceivers can tolerate a certain amount ground shift; see the specified common-mode range. If the ground shift can be larger, you probably need an isolated transceiver.

  • 0
    TI__Mastermind 26736 points

    Terry,

    Clemens's comment is correct. Additionally, see this application note (SSZTB40) from TI regarding some tips for split versus standard termination.

    Additionally, can you confirm L5 and L6 on the schematic? It is more common to place a common-mode choke here. Confirming whether that is the configuration intended.

    R21 needs to be a capacitor instead of a resistor. Generally, this split capacitor is something like 4.7nF. Other values between 1nF and 100nF can also be fine.

    Sometimes, inductive elements like L5/L6 can actually cause significant transients in noisy environments which pose a risk of damage to the transceiver. See this application note (SLLA271) for more details.

    Best,

    Danny

    P.S. You can click on images in posts on E2E to bring them full-screen which should increase clarity.