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TPS65987DDJ: Unable to enter Fast Role Swap

Gim Song
Intellectual 1110 points
Part Number: TPS65987DDJ
Other Parts Discussed in Thread: TPS65987D

Hi,

Our customer is designing a simple full speed USB device (dongle using TPS65987DDJ) with USB type C connector that will connect to a handphone (with USBC) and another connector for external power supply/adapter to the dongle. Below is the use case:

1) No external power supply connected to the dongle; the handphone will supply power (5V) to the dongle.

2) External power supply (5V) connected to the dongle; the dongle will provide power on the Vbus can charge the handphone.

3) Dongle will always be UFP.

4) Condition 1) and 2) can be switched anytime (Power Role Switch) but the data must still be connected.

We follow the Fast Role Swap based on the app note http://www.ti.com/lit/an/slvae20/slvae20.pdf on TPS65987EVM by setting Automatic Sink Cap (0x29) and Fast Role Swap Supported (0x42)

However, we are unable to get FR Swap Msg (able to see Fast Role Swap Event Type).

Please refer to the attached.

a) Waveform of VBUS for FRS from 5V drop to 0V and then recover to 5V when the barrel jack is removed from TPS65987D EVM

b) pjt file used on TPS65987D EVM as Dongle.

c) CC log showing FR Swap Event but not showing PD Msg for Fast Role Swap

Thanks.

Gim Song

  

TPS65987D_Audio_Dongle_EVM_Advanced_FRS_18092019.pjt

  • 0
    TI__Intellectual 1110 points

    Below is CC log which did not manage to add in the previous post, this is captured when the barrel jack is removed from TPS65987EVM (as dongle).

  • 0 in reply to Gim Song
    TI__Mastermind 36751 points

    Hi Gim Song,

    In this case, you are required to do a Fast Role Swap (FRS) from a Source to a sink. There are some more configuration settings required for this use case.

    1. Need to adjust the 5V PDO in the Transmit Sink Capabilities. There is a field for "Fast Role Swap Required USB Type-C Current" Set this to "5V, 3.0A"

    2. By default, the FRS event will be triggered by UVP from the TPS65987DDJ. In this case, it may already be too late as VBUS has dropped too far below 5V. I would recommend using a GPIO event from the TPS65987D that connects to the external charger and connect it to a GPIO on the TPS65987D that connects to the phone. You can use the Plug Event GPIO event for the charger port and "Port1 FRSwap Input Event" as the GPIO event on the TPS65987D that connects to the phone. This would allow you to send the FRSwap message earlier when the charger is disconnected.

    3. The dongle needs to have a lot of capacitance on the System Power rail in order to keep VBUS alive during the transition. The recommendation is 600uF minimum. Please read the following White Paper on Fast Role Swap dongle design: http://www.ti.com/lit/wp/slyy147/slyy147.pdf

    Thank you,
    Eric