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TPS25751: Does the TPS25751 have an FRS function?

takeshi tozawa
Prodigy 41 points
Part Number: TPS25751
Other Parts Discussed in Thread: TPS65987DDK

Tool/software:

Hi TI experts，
Could you please tell me if the TPS25751D has a fast role swap function?

The intent of the question is as follows:

I am designing a product that connects to a tablet via USB.
The product is connected to an AC adapter and battery, and supplies USBPD 45W to the tablet.
It also performs USB communication (USB3.2) at the same time. It is a product similar to a USB-C HUB.
The PD controller uses the TPS25751D.

USBPD is set to be enabled only when the device's AC adapter is connected.
The circuit is configured so that VBUS drops when the AC adapter is not connected (when only the battery is connected).
In contrast, we want USB communication to be enabled regardless of the power connection state, but communication is interrupted when the AC adapter is
unplugged. We think this is because FRS is not activated, and would like to know the specifications of the TPS25751.

Best Regards,
Takeshi Tozawa

  • 0
    TI__Mastermind 34436 points

    Hi Tozawa-san, 

    TPS25751 does not support FRS (FR_Swap or Fast Role Swap) function. Is the device (with TPS25751) unable to maintain power from the battery when the AC adapter is disconnected? 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 41 points

    Hi Raymond,

    Thank you for the answer.
    However, this has become fatal for me.

    I want to stop USBPD immediately after unplugging the AC adapter from the product.
    This is because the battery power is insufficient.
    Also, changing to a higher power battery is not realistic.

    If the FRS function is not available, it is possible to perform renegotiation and transition to power sink
    when the AC adapter is unplugged, but this is not realistic as it would require the battery to provide power
    for the USBPD for several seconds during the negotiation period.

    Also, since changing to a PD controller with FRS function is not realistic, it would be ideal if there was a way to give
    the TPS25751 a function similar to FRS by adding some kind of circuitry.
    Is there any way to do this?

    Best Regards,
    Takeshi Tozawa

  • 0 in reply to takeshi tozawa
    TI__Mastermind 34436 points

    Hi Tozawa-san, 

    Unfortunately since TPS25751 does not support FR_Swap messages it will not be able to support a fast role swap even with additional circuitry. You can configure TPS25751 to prefer a certain power role upon connection in order to prevent a disconnect using the Try.State configuration field in register Port Configuration (0x28). 

    Other PD devices such as TPS65987DDK does support FR_Swap, however it is not pin to pin with TPS25751. 

    Thanks and Regards,
    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 41 points

    Hi Raymond,


    Thank you for your answer. I tried the Try.State setting field of the register Port Configuration (0x28) (Try.SRC or Try.SNK).

    The result was not good.

    It seems that it also depends on the compatibility with the other tablet.

    After unplugging the AC adapter, VBUS will drop, but some devices stop USB communication when VBUS becomes low voltage.

    On the other hand, there are other tablets that do not stop communication even if VBUS drops to 0V. In this case, there is no problem for me.

    Do you know what the difference is?

    After that, I would like to consider reselecting the PD controller. The TA of the TPS65987DDK is insufficient on the low temperature side.

    -21°C or lower is required.

    It seems that TPS65987DDHRSHR is available as a temperature expansion product, but is my understanding correct?

    Best Regards,
    Takeshi Tozawa

  • 0 in reply to takeshi tozawa
    Prodigy 41 points

    I'm sorry again and again.

    I referred to this link for information on wide temperature products.

    (+) TPS65987D: TPS65987 vs TPS65994 - Power management forum - Power management - TI E2E support forums

    Best Regards,
    Takeshi Tozawa

  • 0 in reply to takeshi tozawa
    TI__Mastermind 34436 points

    Hi Tozawa-san, 

    The temperature range also applies to TPS65987DDK. TPS65987DDH is an older version that only supports PD3.0 while TPS65987DDK supports PD3.1. Outside of the temperate range both devices do support FR_Swap and is configurable through the Application Customization Tool (different GUI from TPS25751). 

    Thanks and Regards,

    Raymond Lin