Other Parts Discussed in Thread: THVD1400,
Tool/software:
Hi
We are evaluating the use of your THVD1400VDRCR RS-485 transceiver in an application that involves interfacing with an SAE J1708 bus, commonly used in heavy-duty vehicle diagnostics and communication systems.
We would like to confirm whether the THVD1400 is suitable for use as a transceiver on a J1708-compliant bus, and if not, what technical limitations or concerns we should be aware of.
Our primary concern is that SAE J1708 specifies a single-wire, open-drain physical layer, in which:
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Nodes must only pull the bus low, never drive it high (i.e., open-collector/open-drain logic).
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Bus idle is defined as high via pull-up resistor, and multiple nodes may attempt to pull low simultaneously (wired-AND topology).
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The physical interface must support multi-master arbitration and non-destructive collision handling.
However, the THVD1400 is a full-duplex RS-485 transceiver that drives the bus differentially and push-pull, which raises concerns about:
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Potential for bus contention or driver damage in case of simultaneous transmissions
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Non-compliance with the electrical and arbitration characteristics expected by J1708
Could you please clarify:
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Whether TI recommends or discourages using THVD1400 for J1708 interfacing
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Whether it can be configured in a way that mimics open-drain behavior (e.g., only driving A/B low, with DE control)
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If not recommended, does TI offer any alternative ICs or reference designs that are J1708-compliant?
We appreciate any insight or guidance you can provide to ensure electrical and protocol compliance for our design.
Regards,
Ajay
