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TCA4307: Hot swap-spi,i2c

Rajkumar S
Prodigy 80 points
Part Number: TCA4307
Other Parts Discussed in Thread: AFE4490, TMP117,

We are in the process of developing modular devices for our system, integrating sensors from Texas Instruments – AFE4490, AFE-DS1191, and TMP117. The communication interfaces for these sensors are AFE4490-SPI, AFE-SPI, and TMP117-I2C.

Each sensor is built on a separate PCB. AFE4490 and AFE-DS1191 will connect to the MCU via a USB connector. It's important to note that the USB connector is used only for board-to-board connecting purposes and does not serve as a USB interface. The mainboard had a one USB C female connector. Only one board(AFE4490/AFE-DS1191) is connected to the main board at a time via the UCB C connector. TMP117 connects via Pogo Pins, Please refer to the attached document for a detailed look at the block diagram.

https://drive.google.com/file/d/1UiTXFteam8fYgxxR-UmdIdSTkzRdp82Y/view?usp=sharing

Sensor attachment and detachment can occur without powering off the device(Hot Swap). I'm curious to know if this modular concept will function seamlessly without any issues.

1. During the development of this modular concept with hot swap, what hardware design considerations should be taken into account?

2. Additionally, could you recommend any specific ICs or solutions to ensure the successful implementation of the modular system with Hot Swap?

Thanks

Regards

rajkumar

  • 0
    TI__Mastermind 30453 points

    Hi Rajkumar,

    TCA4307 is a hot-swap buffer made for I2C. SPI signaling would not be compatible with this device, nor would USB.

    The block diagram makes it seem that your system is only using USB. It looks like you need hot swap capability USB? I am correct here? You might want to look at the USB redrivers and multiplexers team at TI. 

    https://www.ti.com/interface/usb/redrivers-multiplexers/overview.html

    Editing my reply, 

    I believe the TCA4307 would most likely exist between the main PCB and the TMP117 / MLX90632 modules. TCA4307 would be a good device to use here for a hot-swap situation. The typical application of inserting an i2c device into a live backplane can be found on page 15 of the datasheet in section 8.2.4 Typical Application on a Backplane. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 80 points

    Thank you for your prompt response.

    I understand the achievability of I2C hot swap.

    Regarding the connection of SPI (AFE4490/AFE-DS1191), there seems to be a misunderstanding. To clarify, we are employing a custom-made USB-C connector, functioning similarly to pogo pins, for board-to-board connections. It's essential to emphasize that this is not for USB interface communication.

    Now, the challenge is to enable hot swapping for the SPI function.

    For clarity purposes, I framed it as a model where the SPI system operates as a hot-swappable model using pogo pin connections instead of a USB-C connector.

    How can we achieve hot swapping for the SPI system in this setup?

    Thanks

    Regards

    Rajkumar

  • 0 in reply to Rajkumar S
    TI__Mastermind 30453 points

    Hi Rajkumar,

    We do not have a hot-swap buffer for SPI signals. The TCA4307 device is a hot-swap I2C buffer. Being that SPI is a 4-wire interface, I am not certain we can take an I2C hot swap buffer and apply this device to a SPI solution. 

    There are ways to implement hot-swap discretely using i2c 

    In a similar way for SPI, there might be an opportunity to use some device like TS3A4751 to control the switching. Then there needs some type of GPIO expander in order to implement some type of presence detect that would trigger an interrupt to the MCU letting the MCU know a device has been connected. From there, the SPI channels can be enabled to the backplane. 

    Regards,

    Tyler