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P82B96: P82B96

Jacobo Aguillon-Garcia
Prodigy 165 points
Part Number: P82B96
Other Parts Discussed in Thread: SN74LVC2G06, SN74LVC07A, , TCA9517A, INA260, ISO1540

Hello!

I'm new in this I2C technology and I'm trying to assemble a voltage/current sensor (input voltage of the system U5 and voltage/current of the DC/DC converter U6).

The MCU will be the launch board F28377S and I observed that the I2C has no pull-up resistors on it. I just want to do the design as tight as possible and avoid the use of the buffers as SN74LVC2G06 and SN74LVC07A. 

I found that the P82B96 can do the trick in a single package. But I doubt to tie the RX/TX (the datasheet said there is no problem), but then, how is it managed the bidirectionality in that line?

Any feedback is welcome, thank you.

  • 0
    TI__Mastermind 49110 points

    Hello,

    The P82B96 is meant to have RX tied to TX and RY tied to TY when you need the bidirectional feature. For the I2C data line, this is necessary (so in your case RX MUST be tied to TX) but the clock line in I2C is TYPICALLY unidirectional and controlled by the master. The only time you would need to have a bidirectional clock is if your I2C slave supports clock stretching.

    If you are planning to use the device in the unidirectional state, tie RY to a pull up resistor.

    Lastly, I wanted to double check to see if you picked the correct device for your application. Typically the P82B96 is used for long distance communication across a cable. An I2C buffer I usually recommend is TCA9517A for onboard communication or level translation purposes. P82B96 is usually seen in more specialized use (typically DDC compliance in HDMI systems).

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 165 points

    Hello Bobby,

    Thank you for your replay!!

    The advice on the distance it is interesting, the length between MCU and the telemetry stage (INA260) is less than 30cm and it makes me wonder the use of the P82B96. I just found the TIDA-10608 (below) where it has the P82B96 in an isolated fashion and that's the reason I chose it (I will use isolation in my final design).

    The complete design will consist of 43 sensors in total and TCA9517A seems affordable in the long run. I just don't want to deal with so many EN lines as in TCA9517A's datasheet (I'm still trying to figure out the MCU to be used), but I guess I just put EN on high and all is done.

    Is there any TIDA-xxxxx for an isolated TCA9517A design as the P82B96 has?

    I appreciate your help and suggestions.

    Regards.

  • 0 in reply to Jacobo Aguillon-Garcia
    TI__Mastermind 49110 points

    Hello,

    It looks like that TI Design you referenced is able to work because the P82B96 has unidirectional pins which can interface with other devices well. The TCA9517A does not have this kind of feature so there is not a TI Design based around the TCA9517A like this.

    With that said, I am wondering why the ISO1540 can't be used if you are looking for an I2C Power Isolation solution. My only additional comment if you decide to go with ISO1540 is side 1 has a capacitance requirement of less than 50pF and has a VoL of ~800mV. You may want to pair it with TCA9517A (Make A side of TCA9517A face side 1 of ISO1540). This will addess the Large VoL down to ~500mV and buffer the side 1's capacitance limit.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 165 points

    Hello Bobby,

    Wow!...that was exactly what I was looking for!!  

    Thank you a lot, I'll change my design to ISO+TCA and follow your suggestions.

    Thank you again for your time, Regards.