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P82B715: solution of off board sensor ( 2 meter)

Nam, Dino
Expert 6385 points
Part Number: P82B715
Other Parts Discussed in Thread: TCA9543A

Dear team, 

My customer is looking for a solution to communicate with the sensor board that is 2 meters away from the main board.  

Firstly, I recommended to use P82B715 but the customer concern using 3.3V power supply because of recommending supply voltage (Min 4.5V) from datasheet. 

Please review my concept like below and let me knot your opinion which solution is better and concern.   

- Main board supply 3.3V only, they can use 5V at sensor board 

- For 1st concept : Can I use only 3.3V supply to cover this solution? 

- For 2nd concept : Can TCA9543A conver 2 meter off system? 

Thank you. 

  • 0
    TI__Mastermind 21675 points
    Hello Dino,
    I think we need to get more information about the customer.
    A) What cable are they using? It should have some sort of pF/m specifications. That will give use the amount of bus capacitance due to the wiring harness. If they don't have a spec, find out the gauge of the wires at the very least and we can do some estimates. If the capacitance is minimal then you might not need the P82B715 and might be able to get away with different buffer.

    B) What mode of operation are they using? Standard (100 kHz), Fast Mode (400kHz), or Fast Mode Plus (1,000 kHz)???

    Here is direct comment to your diagrams:
    1) The part will work at 3.3V but you might have some performance issues depending on the speed required and the amount of capacitance on the lines. 2 meters shouldn't be to bad. Once we get more information from the customer we can better assess the problem.

    2) Using the TCA9543A with the P82B715 won't work the way you have drawn it. The P82B715 must be used in pairs. Not sure what you are trying to do with the I2C switch, please elaborate on what you are trying to do.
    -Francis Houde