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Original question:

TPS25750: Provide power from BQ charger when TPS25750 configured as a DRP

TPS25750: Reverse mode

Manuel Dieguez
Prodigy 140 points
Part Number: TPS25750
Other Parts Discussed in Thread: BQ25756, , TPS25751, LM76005

Hello forum,

We are currently in the process of designing a bidirectional charger using the BQ25756 charger and the TPS25750 power delivery controller for a 10S battery. We've been successfully charging the battery with different charging profiles, but now we're exploring the possibility of making it reversible to use the battery as a charger.

This leads us to a question: Is it possible to configure the TPS25750 in source mode as well, with a profile set to 20V, for example? We've come across some examples of bidirectional mode usage, but they always involve a separate regulator connected to PP5V. Is it feasible to achieve this solely using PPHV?  In source mode, does it require a separate regulator?

Thanks

 

  • 0
    TI__Genius 13880 points

    Good Afternoon Manuel,

    I want to highlight our new product, the TPS25751. This is a follow on to the TPS25750. It is pin to pin compatible, and incorporates some new features as well as fixes some issues found on the TPS25750 when paired with battery chargers. We are strongly advising all new designs use the TPS25751 instead of the TPS25750.

    To answer your question, you will need a regulator to provide 5V to PP5V, as it powers the Type-C state machine as well as the USB-PD policy engine of the TPS25750. This answer would also apply to the TPS25751. This EVM schematic provides more detail to my answer (the EVM can source and sink power); Figure 4.3 shows the power stage schematic for supplying PP5V from VSYS.

    Kind regards,

    Conner Gillette

  • 0 in reply to Conner Gillette
    Prodigy 140 points

    Dear Conner,

    Thank you for your response and for highlighting the TPS25751 as a recommended alternative to the TPS25750, along with its new features and enhancements.

    Regarding your explanation, I understand that a regulator is required to provide 5V to PP5V, as it powers the Type-C state machine and the USB-PD policy engine of both the TPS25750 and TPS25751. I noticed in the EVM schematic that it uses a 5V regulator (LM76005) with the capability to deliver 3A. We are interested in using the buck-boost feature of the BQ25756 as the source to deliver 5V/3A. Is this feasible? If so, can a 5V regulator with a lower capacity be used to power the state machine? What value would you recommend?

    Thank you for your assistance.

  • 0 in reply to Manuel Dieguez
    TI__Genius 13880 points

    Yes, the TPS25751 will work "out of the box" with the BQ25756; When using the TPS25751 configuration GUI, you will be able to select the BQ25756 as your desired charger, and a fill out a few necessary parameters (battery charging voltage, battery charging current, charge termination current and pre-charge current).

    If you are only using a 5V contract (as opposed to 9V, 15V, or 20V), you wouldn't need a 5V buck in addition to the BQ25756, as the BQ25756 could be configured to output 5V. If you want to use additional voltage contracts, I would use the 5V regulator. As far as recommendations, I would recommend the LM76005.

    Kind regards,

    Conner Gillette

  • 0 in reply to Conner Gillette
    Prodigy 140 points

    Dear Conner Gillette,

    Thank you for your detailed explanation.

    I understand that the TPS25751 offers two current paths: one from PPHV to VBUS of 5A and another from PPV5 to VBUS of 3A (as depicted in the diagram). Our goal is to utilize only the 5A bidirectional current path to use it as both a source and a sink. We plan to connect a low-capacity (< 100mA) 5V regulator to PPV5 to power the state machine. Is this configuration feasible? If so, I fail to see the necessity of using a 5A regulator in PPV5.

    Additionally, currently, we are using the TPS25751 as a sink, and the PPV5 pin is connected to GND. Does the state machine require a regulator on PP5V only when configured as a source?

  • 0 in reply to Manuel Dieguez
    TI__Genius 13880 points

    To your first point, I don't see an issue with that configuration. Make sure your Source PDO1 uses PP3/PPHV (these power paths are the same: The TPS25751 does a better job at unifying the naming conventions) if you are planning on having your 5V contract capable of sourcing more than your low-capacity regulator can provide.

    To your second question, yes that is exactly correct.

    Kind regards,

    Conner Gillette