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TPS26750: Documentation on BQ25756 control strategy. PPS/AVS Sink for Charging?

Nathan Langford
Prodigy 70 points
Part Number: TPS26750
Other Parts Discussed in Thread: BQ25756

Tool/software:

Hello,

Where can I find information on precisely how the TPS26750 controls the BQ25756 battery charger IC? I'd ideally like to know all of the BQ25756 registers that are being configured, when they are configured, what they are configured to, etc. Looking in the TPS26750 technical reference manual, I cannot find any references to BQ control parameters, even though several are configurable by the EEPROM patch generated with the Application Customization Tool.

Access to this information would probably answer my other question: Does the TPS26750 automatically configure itself as a PPS or AVS sink at a voltage slightly above the battery pack voltage to maximize the efficiency of the buck-boost charger?

Thank you,

Nathan

  • +1
    TI__Mastermind 34256 points

    Hi Nathan, 

    Upon boot-up, TPS26750 configures BQ25756 VFB_REG (Q14), ICH_REG (Q15), ITERM (Q16), and IPRECH (Q17) based on the values set in the GUI questionnaire page. Additionally, during PD operation TPS26750 automatically configures the following register based on different PD scenarios:


    Source: PD automatically configures BQ25756 register 0x0A (Reverse Mode Input Current Limit) and register 0x0C (Reverse Mode Input Voltage Limit) based on the negotiated PD contract. 

    Sink: PD automatically configures BQ25756 register 0x06 (Input Current DPM Limit) and register 0x08 (Input Voltage DPM Limit) based on the negotiated PD contract. The input voltage/current DPM limit is configurable through the GUI questionnaire. 

    Power Role Swap: PD disables BQ25756 reverse and forward mode control, additionally the PD sets BQ25756 reverse mode voltage/current back to default safe 5V/900mA. 

    Detach or Hard Reset: PD disables BQ25756 reverse and forward mode control, additional the PD sets BQ25756 reverse mode voltage/current back to default safe 5V/900mA. 

    Nathan Langford said:
    Access to this information would probably answer my other question: Does the TPS26750 automatically configure itself as a PPS or AVS sink at a voltage slightly above the battery pack voltage to maximize the efficiency of the buck-boost charger?

    An EC/MCU needs to update TPS26750 Autonegotiate Sink register 0x37 to request the voltage/current level it desires. TPS26750 does not automatically configure the PPS/AVS voltage and current request based on the battery pack voltage. Refer to TPS26750 TRM for more details (screenshot below shows relevant register and field for sink PPS and AVS):

    Let us know if you have any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 70 points

    Thank you! That answers my questions.

  • 0 in reply to Nathan Langford
    TI__Mastermind 34256 points

    Hi Nathan, 

    No problem, please let us know if you have any further questions or concerns in a new e2e thread for better tracking! 

    Thanks and Regards,

    Raymond Lin