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TMDS171 - Internal circuit of 3 level input pins

Kawai
Guru 19785 points
Other Parts Discussed in Thread: TMDS171

Hello Team,

Could you please share us the internal circuit of the 3 level input pins of TMDS171 (PRE_SEL, EQ_SEL/A0, TX_TERM_CTL, SWAP/POL pins) ?

When you float this pin and monitor the pin voltage, DMM showed 0.9V which is out of the Vim range. Instead of floating the pins and used 65kOhm pull up/down resistors like in the application schematic in the datasheet, DMM showed 1.4V. This is the maximum value of the recommended range. We would like to know how to set the pin voltage to the middle of the Vim.

Best Regards,

Kawai

  • 0
    TI__Mastermind 23815 points

    Hi Kawai-san,

    The range for Vim in DS has a note at the end of the table:

    These values are based upon a microcontroller driving the control pins. The pull up/down/floating resistor configuration will set control
    pins properly which will have a different value than shown due to internal biasing.

    You don't have to worry about the voltage in the pin, NC will work fine.

    Regards

  • 0 in reply to Moises Garcia
    Guru 19785 points
    Hello Moises-san,

    I understood that the VIM spec voltage range is the required output level from the external controller devices. Thank you for the information.

    Best Regards,
    Kawai