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TPS65988: Looking for options of dynamic power limiting in a USB PD supply

Perry Watson
Prodigy 30 points
Part Number: TPS65988

I'm doing research for a project for a new power supply product to provide USB PD charging capability to multiple USB chargers on seats in an airplane. The problem is, the airplane power system has a limited power budget. Not every seat will be able to pull >60W at the same time.

Our idea was to have multiple USB PD controller modules throughout the plane, each powering some subset of the seat chargers. The modules would communicate with each other via a Bluetooth Mesh network to monitor the overall power demand and dynamically throttle the power to some of the USB PD controllers.

Is it possible to tell a USB PD controller, such as the TPS65988, that it is not allowed to provide power above a certain threshold? USB PD can normally go up to 100W, but could we send a signal to this chip, perhaps via I2C, to tell it that it is not allowed to provide more than, say, 15W? Please advise. Thank you.

  • +1
    TI__Mastermind 18300 points

    Hi Perry,

    If you are doing a power only application (no USB Data/video), I would recommend looking at the TPS25751. It is a cheaper option than the TPS65988DK family which are designed to support data as well.

    You should explore the TRM (Technical Reference Manual) and specifically look at the Transmit Source Capabilities Register (0x32) and the 'SSrC' 4CC command. The register is where we store the advertised PDOs (Power Data Objects) for sourcing from USB-C, and you can update the register over I2C to reflect your current power capabillity. The 'SSrC' command would need to be sent to renegotiate PD contracts if one is already negotiated on the port that is changing power levels. These registers and commands are used through I2C and described in the TRM.

    The devices have 4 configurations for I2C address.

    Perry Watson said:
    Is it possible to tell a USB PD controller, such as the TPS65988, that it is not allowed to provide power above a certain threshold? USB PD can normally go up to 100W, but could we send a signal to this chip, perhaps via I2C, to tell it that it is not allowed to provide more than, say, 15W? Please advise. Thank you.

    Yes, the Transmit Source Capabilities Register stores the Source PDOs that we will advertise when connected to a USB-C PD Sink device. You can think of a PDO as a Power Contract, that specifies the Voltage and Max current available at that voltage. These PDOs can be updated to reflect available power.

    Thanks and Regards,
    Chris Lim