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TAS5731M: ADR/FAULT pin - is it push-pull or open-drain?

Daniel Germann1
Prodigy 130 points
Part Number: TAS5731M


The TAS5731M datasheet describes the ADR/FAULT pin as "dio", digital input / output.  But this same description is also used for the SDA pin, which is typically open-drain (standard I2C).  However, in section 7.6 of the datasheet, both ADR/FAULT and SDA have a definition for "high-level output voltage", which does not seem consistent with an open-drain output.

Is the ADR/FAULT pin push-pull or open-drain when configured as the FAULT output?  We are designing a system that will use two TAS5731M amplifiers, and if we can just strap ADR/FAULT low for one and high for the other (through 15k resistors, as described in the datasheet) and still be able to use the FAULT output, we're good to go.  But if we need some additional circuitry because it is an open-drain output (like SDA, which has the same specifications in the datasheet), we want to be sure to add that before the PCB goes out.

Thank you!

-Dan

  • 0
    TI__Mastermind 24835 points
    Hi Daniel,
    ADR/FAULT pin is an input pin only during power up. After the I2C address is latched during power-up, this pin is used as a fault notification output. The pin is driven to low when a fault occurs.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 130 points

    Hi, Shawn.

    Yes, the datasheet describes the pin in that way.  However, the datasheet is somewhat confusing as to whether the pin is actually driven high when the fault condition is removed or whether it expects a pull-up resistor to pull the pin back high.  The specifications for SDA and ADR/FAULT are both listed as "dio", SDA is an I2C bus pin (typically open-drain bidirectional I/O) and the I/O characteristics of both SDA and ADR/FAULT are described together in the datasheet.  Since SDA, being an I2C bus I/O pin, is typically an open-drain output, and both pins are described together, it makes me wonder if ADR/FAULT is also an open-drain output.

    So I am still unsure as to whether, after power-up, when the ADR/FAULT pin is configured as a FAULT output:

      * the ADR/FAULT pin is a push-pull output (driven low when a fault occurs, and driven high when the fault condition is removed) or

      * the ADR/FAULT pin is an open-drain output (driven low when a fault occurs, but requiring an external pull-up resistor to pull it high when the fault condition is removed)

    Can you confirm which description is correct?

    Thank you!

    -Dan

  • 0 in reply to Daniel Germann1
    TI__Mastermind 24835 points
    Hi Dan,
    The first description is correct and pull-up resistor is not necessary.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 130 points

    Hi, Shawn.

    Perfect.  So we can have two TAS5731M's on the PCB, one with ADR/FAULT pulled low with a 15k resistor and the other with ADR/FAULT pulled high with a 15k resistor, and both pins can generate a FAULT output to our CPU.

    Thanks for the clarification!

    -Dan