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P82B96: TCA9511A / P82B715: Compatibility for Hot-Swappable, Long-Range I2C Bus

Kittitouch Lelapiyamit
Prodigy 20 points

Part Number: P82B96
Other Parts Discussed in Thread: TCA9511A, P82B715, TCA9617B

Hi TI Support Team,

I am designing an I2C system that requires both hot-swap protection and long-range bus extension, and I have the following questions regarding using the TCA9511A together with the P82B715:

1. Is it technically feasible to use the TCA9511A and P82B715 together in the same I2C signal chain?

2. What is the recommended placement order — should the TCA9511A be placed before or after the P82B715?

3. Are there any known compatibility issues, timing conflicts, or voltage level concerns when combining these two devices?

Thank you for your time and guidance!

Best regards,
Kittitouch

  • 0
    TI__Guru 61061 points

    Hi Kittitouch,

    We are still looking into this and will provide an update shortly.

    Regards,

    Jack

  • 0
    Prodigy 20 points

    Hi Jack,

    Thank you for your prompt response.

    Our hardware engineer has selected the TCA9617B for our design. Could you clarify whether it offers the same functionality and performance as the TCA9511A or P82B715 for our use case?

    Additionally, if you have a recommended product better suited for long cable runs with hot-plug capability, we would greatly appreciate your guidance.

    Best regards,
    Kittitouch

  • 0 in reply to Kittitouch Lelapiyamit
    TI__Guru 65908 points

    Hi Kittitouch,

    TCA9617B is our fast mode+ I2C buffer (up to 1 MHz) and buffers two I2C segments of 550pF each (A-side and B-side). 

    TCA9511A is a hot-swap buffer, it can support 400 pF on each side of the buffer, works up to 400kHz fast mode speeds. It also has hot-swap functionality - it tracks the input side and waits for both sides to be idle / detects an I2C stop condition before connecting the input to output - often used in carded applications where an unpowered card is inserted into a live backplane. 

    P82B715 is a bus extender capable of increasing output drive to handle up to 3000pF on the transmission side of the buffer. Usually used for longer cable applications but is more expensive. 

    How long is the cable / trace? TCA9617B has plenty of drive strength (up to 30mA) on its open-drain drivers. The TCA9617B doesn't have smart hot-swap circuitry, but it is high-z from A-side to B-side as long as EN is held low, or if one supply is powered down. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 20 points

    Hi Tyler,

    Thank you for the clear explanation — that really helped!

    After reviewing the options, I've decided to go with the TCA9617B for my application. The cable length will be around 1–2 meters, so the 30mA drive strength should handle that well. I understand it doesn't have built-in hot-swap circuitry, so I'll implement my own logic to manage that on the system side.

    For customers who require very long cable runs, I plan to offer the P82B715 as an option to handle the higher capacitance.

    Does this approach make sense to you? Any concerns or suggestions would be greatly appreciated.

    Best regards,
    Kittitouch

  • 0 in reply to Kittitouch Lelapiyamit
    TI__Guru 65908 points

    Hi Kittitouch,

    Will you use a pair of TCA9617B's? I recommend using one buffer on both ends of the cable. 

    A-A, A-B, B-A  connections are all allowed. 

    B-B connections are never allowed. 

    See this app note for more details.

    https://www.ti.com/lit/an/scpa054/scpa054.pdf?ts=1719932118796&ref_url=https%253A%252F%252Fwww.google.com%252F

    Regards,

    Tyler