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SN65HVD33: Measure for unstable startup

Satoshi
Guru 19645 points
Part Number: SN65HVD33

About startup timing for SN65HVD33; when differential signal(Y and Z) start immediately after DE enabled, waveform is unstable.

Waveform is attached below,

※ Yellow: 9pin(Y), Blue: 10pin(Z), Purple: 4pin(DE), Green: 5pin(D) 

Please let me know about two points below;

①I think that Differential signal should start after "Driver enable delay with bus voltage offset" (datasheet P11, 900ns_max), is it correct?

②When attached external fail-safe circuit, this problem was clear.

　Is this idea right way? And, is there the other measure?

Best regards,

Satoshi

  • 0
    TI__Mastermind 25705 points

    Satoshi-san,

    Can you help clarify a few things? 1) do you have any termination resistors on the bus? If so, what's the value? 2) What's the REB pin status when the DE was toggled?

    Your understanding about the delay spec is correct. If the bus had been biased to 2V, it would make the driver (especially the P side) harder to be turned on therefore the delay is much longer than the normal condition (starting from 0V Fig 22). Please let me know if this would generate any issues in your application.

    Regards,

    Hao