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TPS65987D: Discrepancies between datasheet and TUSB1146EVM implementation.

KevinMD
Prodigy 130 points
Part Number: TPS65987D
Other Parts Discussed in Thread: TUSB1146EVM

Hello, this question was posted in the TUSB1164EVM discussion, but I was asked to repost here since it specifically deals with the TPS65987D implementation.

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Looking at the TUSB1146EVM, I had a couple questions regarding the TPS65987D implementation:

  1. The TPS65987D Hardware Guidelines recommend using I2C1 for the host controller, I2C2 for Thunderbolt controller, and I2C3 for the external Mux. However, on the TUSB1146EVM, the TPS65987D uses I2C1 for the Mux, I2C2 not used, and I2C3 for the programming header. Is there a correct way? I didn't see a way to change this using the programming GUI, but maybe I missed it.
  2. TPS65987D datasheet recommends floating unused GPIO, but TUSB1146EVM pulls all used to ground with a 100k. Which is correct?
  3. TPS65987D datasheet recommends PPHV1 as a sink path and PPHV2 as a source path, however TUSB1146EVM does the reverse. This appears to be configurable in the GUI, so why would it matter and what is preferred?

Thanks

  • 0
    TI__Mastermind 36751 points

    Hi Kevin,

    1. The TPS65987D I2C1 interface is configurable to be either a controller or a target. The I2C2 interface is a target only and the I2C3 interface is a controller only.

    2. The TPS65987D datasheet has suggestions for how to terminate each GPIO if unused. Most are suggested to float if unused and some are recommended to be terminated with a resistor. In general, most GPIOs are High-Z if unconfigured.

    3. The power paths are configurable to be source/sink. We recommend to use one as source and the other as sink as the suggestion is consistent with all our hardware examples. As long as your hardware matches your configuration, no issue with swapping them.

    Thank you,
    Eric