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Original question:

USB-C-PD-DUO-EVM: FTDI functions installed in EVM

USB-C-PD-TKT-EVM: USB-C-PD-DUO-EVM Does not Startup App if FTDI is powered

Eric Lewis
Prodigy 50 points
Part Number: USB-C-PD-TKT-EVM
Other Parts Discussed in Thread: TPS65987D

Tool/software:

I'm working with a reference design with the TI USB-C-PD-DUO-EVM. The issue I currently have is that if a micro USB cable is connected to the power duo source port and the SPI_CS jumper is set to the SRC board, the source board won't boot the application and won't power the sync port. Here's what I observe:

chip select src on startup

Measuring the source pin

FTDI controller powered up first 2.5V without base powered

With base powered comes up to 2.8V

Moving the jumper to SNK this comes up to 3.24V

Moving the jumper to SRC it comes back down to 2.8V

 If I have the SPI_CS jumper start in the SNK position, the board comes up properly.

chip select SNK on startup

Measuring the source pin 3.23V

Moving the jumper from SNK to source

Measuring the source pin 3.29V

The FTDI controller recognizes the pullup and keeps it high.

I am using a reference design with the FTDI controller connected and powered on the same chip select as the TI part. This chip select pulldown is preventing the TPS65987D from sourcing any downstream parts.

  • 0
    TI__Mastermind 37855 points

    Hi Eric,

    I'm seeing similar issues, but not exactly the same. Does the j202 jumper position affect your usage of the EVM? Is there a specific use case or feature you need that this jumper setting is preventing? Is it possible to use the board wit hteh SPI_CS jumper left in the Sink position?

    Eric Lewis said:
    FTDI controller powered up first 2.5V without base powered

    With only the micro-usb connected, I do not see this. I measure 0-V

    Eric Lewis said:
    With base powered comes up to 2.8V

    I can replicate this

    Eric Lewis said:

    Moving the jumper to SNK this comes up to 3.24V

    Moving the jumper to SRC it comes back down to 2.8V

    I can replicate this

    Eric Lewis said:

    Measuring the source pin 3.23V

    Moving the jumper from SNK to source

    Measuring the source pin 3.29V

    The FTDI controller recognizes the pullup and keeps it high.

    I see everything here expect for measuring 3.29V on the source pin.

    What also appears to be strange is that leaving the CS floating and not on any setting also prevents the Source from operating properly. It seems specifically that biasing the CS or SNK pin allows the Src side to boot properly.

    When I break the Source and Sink boards apart, the EVMs work properly as well.

    There may be an issue in the layout that forces you to keep the pins connected to the sink CSZ pin if this works with the boards broken apart.

    Thanks and Regards,

    Chris