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DS160PR410: DS160PR410: Which still pins need to be connected when running in PIN mode

Alecsandru-Neculai Andrei
Prodigy 20 points
Part Number: DS160PR410

Tool/software:

I am using the redriver in PCIe mode with PIN setup. In the documentation it mention that there are some additional pins that should be still pulled up high with a 4.7k rezistor. I am referring to these pins: READ_EN_N, ALL_DONE_N, SCL and SDA.

This is my schematic:

In the example schematic in the documentation for PIN mode, those pins are not connected.

  • 0
    TI__Mastermind 18850 points

    Hi Alecsandru,

    Alecsandru-Neculai Andrei said:
    In the documentation it mention that there are some additional pins that should be still pulled up high with a 4.7k rezistor. I am referring to these pins: READ_EN_N, ALL_DONE_N, SCL and SDA.

    Discussing each pin individually:

    • READ_EN_N should be pulled up to 3.3 V with a 4.7k resistor in Pin Mode according to the pin description on page 4.
      • ALL_DONE_N should be left floating in Pin Mode according to the pin description on page 3.
        • No pullup is suggested for this use case.
      • SCL, SDA: pullups are mentioned to be required to follow SMBus/I2C standards on page 4
        • This is for generic I2C reasons: I2C drivers are open-drain, therefore I2C lines need pullups to represent high voltage levels
        • However, in pin mode the I2C interface is not used.
          • The DS160PR410 EVM connects SCL and SDA with pullups at all times but I believe this is for simplicity reasons, the pullups do not add any functionality in pin mode since the SCL and SDA lines are inactive.
        • Therefore it should be fine to leave SCL and SDA floating with no pullups if the device will never be operated in I2C modes.

      I see some of the example schematics in Section 8 are ambiguous about how these pins should be configured, the pin descriptions should be consulted instead. Let us know if you have more questions.

      Best,

      Evan Su