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TUSB7320 - SDA/SCL pin I/O internal schematic or block diagram

Kawai
Guru 19785 points
Other Parts Discussed in Thread: TUSB7320

Hi Team,

Please let me ask you about TUSB7320.

Our customer request us the internal schematic or block diagram of SDA and SCL I/O pins. Could you share us the information ?

What they must know is that if these pins have weak pull down circuit or not. If there is a pull down or sink circuitry, please share us the resistor or sink current value.

[Background of this question]
Our customer design does not use EEPROM, however, they had designed their board without pull down but pull up on SDA/SCL lines.

This lead to the recognition problem in their system. They must keep SDA/SCL LOW when system power up, but they did not prepare land for pull down resistors. If there is a pull down or sink circuitry inside SDA/SCL pins, they could use larger resistor value such as 1Mohm for pull up resistors.

We appreciate your prompt response.

Best Regards,
Kawai

  • 0
    TI__Expert 4055 points

    Hi Takushi,

    Unfortunately there is no internal pull down on those terminals. Those terminals are open-drain signals and require external resistors.

    There is a way to disable the 'Serial-Bus Interface' (I2C) via software. Customer can disable it by by writing a '0' to the SBDETECT bit at PCI Register B3h (Serial Bus Control and Status Register Description, page 53 of the data sheet).

    Please let me know your thoughts.

    Best Regards,

    Alexis Cortes.

  • 0 in reply to Alexis Cortes9585
    Guru 19785 points

    Hello Alexis-san,

    I greatly appreciate your prompt response.

    I understood that it is an open drain circuit.
    Do you have a leakage current data to these pins ?

    The issue seems to be solved by connecting1Mohm or 100kohm pull up resistor in our customer evaluation. They can see nearly 0V at the pins by using these high resistance and having no problem so far.

    They observed about 150uA sink current to the pins, if this value is a leak current, they think this value is too large.

    Please let me ask if they could try the idea of writing SBDETECT=0 in the PCI register, but it seems that our customer cannot access to SPI registers in their system.

    Best Regards,
    Takushi Kawai

  • 0 in reply to Kawai
    TI__Expert 4055 points

    Hi Takushi,

    I'll have to check this with the design team. Once I have an answer I'll let you know. Anyhow, the best approach here is to disable the serial-interface via software as I mentioned before.

    Best Regards,

    Alexis Cortes.

  • 0 in reply to Alexis Cortes9585
    Guru 19785 points

    Hi Alexis-san,

    Thank you for your support.

    I look forward to hearing from you soon.

    About the software you have told me before, I found the installation manual, however there were no user guide or instruction how to use this tool. Do you think it is easy enough to use without instructions ? Actually, I do not have the environment to test using this tool.

    In addition, I understand the tool only support up to Windows Vista, however, do you know if  this tool will work on Windows8 PC ?

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Expert 4055 points

    Hi Takushi,

    Which software are you talking about?

    Best Regards,

    Alexis Cortes