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TCA9511A: Rise-Time Accelerator Hysteresis

Ryan
Prodigy 10 points
Part Number: TCA9511A


For the TCA9511A, the rise time accelerators specify a 0.6 V threshhold and a slew-rate requirement to trigger. I am curious how sensitive the accelerators are to non-monotonic edges around this threshhold voltage and assuming the slew rate requirement is met. 

Is there anything else in the RTA circuit such as hysteresis that would reduce the possibility of these firing off on a falling edge that is non-monotonic around this 0.6 V threshhold?

Thanks.

  • 0
    TI__Mastermind 25400 points

    Hello Ryan,

    We are looking into your question and will respond soon. Thanks!

    Regards,

    Josh

  • 0
    TI__Guru 50418 points

    Hi Ryan,

    Are you seeing non-montonic edges when using the TCA9511A? 

    My theory is that you wouldn't see non-monotonic edges in the first place since if you do trigger the RTA (with 0.6V threshold and slew rate) then you will see an immediate pull-up current assistance of typically 5 mA towards the supply. The rising edge doesn't seem to have a chance to rise-fall-rise due to the RTA's in the device. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 10 points

    The TCA9511A hasn't been implemented yet, but the product is very risk adverse, so I am trying to verify its operation prior to committing to a design.

    The rising edge does not concern me, it's the falling edge that raises concern. Due to the open-drain configuration, these edges tend to be fast. The RTA also provides good immunity against EMI on the rise, but the RTA doesn't help the fall.

    It is unclear to me if the RTA could fire off if it bounced say from 0.55 V to 0.65 V during a falling transition.  

  • 0 in reply to Ryan
    TI__Guru 50418 points

    Hi Ryan,

    From an internal spec point of view, I was not able to find a set hysteresis around the RTA trigger threshold of 0.6 V. 

    I would need to confirm with our design team to understand this further. Is this information needed to design in the device and if so how fast do you need the info? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 10 points

    Hi Tyler, 

    This is something that I have to thoroughly investigate to meet customer requirements. If you can reach out to the design team and have an answer by the end of the week, that would be very helpful. If it will take longer, please let me know, but I understand everyone is busy in the world.

    I also started this thread in case anybody had this question in the future.

    Thanks for your help.

  • 0 in reply to Ryan
    TI__Guru 50418 points

    Hi Ryan,

    I pinged our design team to double check. It might take till beginning of next week to get a complete answer. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 10 points

    Great. Thanks for letting me know.

  • 0 in reply to Ryan
    TI__Guru 50418 points

    Hi Ryan,

    You're welcome. I'll respond back asap. 

    Regards,

    Tyler