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TPS25751: Schematic Review and Power Dissipation Request for TPS25751 in BQ25792-Based Battery Charger Application and Power Dissipation

Akin Raj
Prodigy 120 points
Part Number: TPS25751
Other Parts Discussed in Thread: BQ25792

Tool/software:

Hi,

We are using the TPS25751 in our design to implement USB Power Delivery input for a 4-cell (4S) battery charger, based on the BQ25792 IC.

The charger handles a battery voltage range of 12V to 16.8V with a Load current ranging from 3.9A to 2.7A.

I have attached the schematics for your review. Kindly take a moment to check and share your valuable feedback or suggestions.

Additionally, we would appreciate it if you could share the power dissipation data for the TPS25751 under these operating conditions, as it is required for our thermal analysis.

  • 0
    TI__Mastermind 34466 points

    Hi Akin, 

    Can you provide a pdf version of the schematic for easier reading? 

    Akin Raj said:
    Additionally, we would appreciate it if you could share the power dissipation data for the TPS25751 under these operating conditions, as it is required for our thermal analysis.

    Can you provide further details on the exact 'operating condition'? Since TPS25751 can negotiate different levels of voltage and current this value may vary. 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 120 points

    Hi Raymond,

    Sorry for the late response, 
    Our operating condition will be 30W power should be provided to battery charger to charge the battery. Please provide the power dissipation data for this scenario.


    Regards
    Akin

  • 0 in reply to Akin Raj
    TI__Mastermind 37855 points

    Hi Akin,

    What do you mean by power dissipation data?

    The datasheet contains the Thermal resistance information.

    Do you have a PDF of the schematics you can share?

    When you say "30-W" at what USB-C PD voltages?

    Is the USC-port sink only?

    Is any data being used?

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    Prodigy 120 points

    Hi Christopher,

    Thank you for your response.

    To clarify:

    • The USB-C PD voltage used will be 15V @ 2A,

    • The port is sink-only, and

    • No data lines are being utilized.

    We’re currently preparing for a thermal simulation. If an Icepak model is available, we would appreciate it if you could share it with us.

    For your reference, I’ve attached the Smart PDF of the schematic. Kindly review it and share your valuable insights, especially regarding the Power Delivery and Battery Charger sections.
    tesseract_power_brd_sch_reva_20may25a.pdf

    Looking forward to your feedback.

    Best regards,
    Akin




  • 0 in reply to Akin Raj
    TI__Mastermind 37855 points

    Hi Akin,

    We do not have Icepak models available.

    Please submit a separate E2E with the BQ part as the primary part for a schematic review from the BQ team.

    I primarily support the USB-C PD products, and will focus my review on that portion of the schematic.

    Here is the feedback on the USB-C PD portion of the schematic:

    • PP5V:
      • For sink only, you can ground PP5V if unused
    • I2C:
      • Ensure there are 3.3V pullups on the I2C lines
      • We do not support I2C multimaster on the I2Cm port
      • You should not tie the I2Cc lines to the I2Ct lines
    • ADCINx resistors:
      • Because you are loading the PD config from an EEPROM, it is recommended to use the ADCIN config for safe mode
      • If you are loading the image from the MCU , always enable sink may be fine
    • GPIO4/5
      • Unused GPIOs can be tied to GND
    • Why is the TVS diode pin 6 floating

    What is your intention with the I2C connections? What should be controlling what? How are you controlling the BQ25792?

    The I2Ct and I2Cc pins of the TPS25751 should not be connected. It should at least look like this.

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    Prodigy 120 points

    Hi Chris,

    Thank you for your prompt review and valuable feedback on the USB-C PD section of the schematic. Please find our responses and clarifications below:

    PP5V:

    • PP5V is connected to GND, as we are operating in sink-only mode.

    I2C:

    • 3.3V pull-up resistors are placed in the EEPROM section and are pulled up to the PD LDO 3P3 supply.

    • Regarding the I2Cc and I2Ct lines: They are currently shorted as part of an internal test configuration. During initial power-up, only the PD acts as the master. There will not be two masters on the bus at any time. We will ensure this connection is updated appropriately before final release.

    ADCINx Resistors:

    • By default, the ADCIN pull-up is configured for Safe Mode. An 8.2k resistor is present to modify the mode when the image is flashed from the SoC, as per recommendation.

    GPIO4/5:

    • These unused GPIOs have been tied to GND.

    TVS Diode (Pin 6):

    • Thank you for catching this. Pin 6 was floating inadvertently, and this has now been corrected.

    I2C Bus Intentions & BQ25792 Control:

    • The PD is the master during power-up and initialization. The I2C lines are currently shared for testing purposes only. The BQ25792 is controlled by the main SoC post-initialization. We will revise the schematic to ensure that I2Cc and I2Ct are not connected in the final version, following your recommendation.

    Please let me know if further clarification is needed or if there are additional suggestions. Also, as advised, we will submit a separate E2E thread for the BQ25792 schematic review.

    Best regards,
    Akin

  • 0 in reply to Akin Raj
    TI__Mastermind 37855 points

    Hi Akin,

    Thanks for the clarifications. Your planned should be fine. I have no additional suggestions at this time.

    I will close this thread now. If you have any questions related to the schematic, feel free to reopen the thread by responding below, otherwise you can submit a new thread for new questions.

    Thanks and Regards,

    Chris