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TPS25751EVM: External Flash TPS configuration not working in Dead Battery Mode

Nicolas Armogathe
Prodigy 120 points

Part Number: TPS25751EVM
Other Parts Discussed in Thread: USB-PD-CHG-EVM-01

Hi Team,

I am reaching out regarding a configuration issue with my TPS25751DREFR design (based on the USB-PD-CHG-EVM-01 evaluation board).

Issue: The controller fails to load the configuration from the external Flash memory when booting in Dead Battery Mode.

Current Setup & Observations:

  • Hardware: My schematic is a direct copy of the USB-PD-CHG-EVM-01 reference design.

  • Boot Pins: Both ADCIN1 and ADCIN2 are tied to GND (i've tried it), which should theoretically set the device to boot from the external Flash when is dead battery mode cf: SafeMode.
    image.png
    image.png

  • Power: The issue occurs specifically when the system is powered via VBUS (Dead Battery condition).

  • Behavior: The device does not seem to apply the configuration from eeprom, resulting in a failure to negotiate the expected Power Delivery profile (always giving 5V when not supposed to, the IC charger that follow it isn't configured either due to the flash config nto being used properly).

Attachments:

  1. My current schematic : USB C PD own.pdf 

  2. The USB-PD-CHG-EVM-01 schematic for comparison : TIDM748A.PDF 

I would like the TPS to load and configure itself using the binary stocked in the EEPROM in any given situation, dead battery mode or not.

Looking forward to your guidance.

Best regards,

  • 0
    TI__Guru 70031 points

    Hello,

    In the schematic it shows that the ADCINs are connected to LDO_1V5.  Please be sure that when you grounded the ADCIN pins the LDO_1V5 is not impaired.   However, if there was an issue with LDO_1V5 you would see it in both the deadbattery and non-deadbattery states.  

    Can you confirm that LDO_3V3 is correct when the USB is first connected (LDO_3V3 is derived from VBUS in deadbattery mode)?

    Can you also confirm what is happening on the I2C lines?  The BQ, EEPROM, and PD are all connected to this bus but in the safeMode only the EEPROM and PD are powered.  Do you know if the BQ is low impedance and thus preventing the I2C comms?

    Regards,
    Chris

  • 0 in reply to Chris Sterzik
    Prodigy 120 points

    Hello,

    " Please be sure that when you grounded the ADCIN pins the LDO_1V5 is not impaired. " It is not.

    "Can you confirm that LDO_3V3 is correct when the USB is first connected (LDO_3V3 is derived from VBUS in deadbattery mode)?" LDO_3V3 is correct when derived from VBUS, as well as LDO_1V5.

    " Can you also confirm what is happening on the I2C lines?  "  when powered by a not dead battery I can see data exchange on I2C. When in dead battery mode there is some data exchange, both SDA and SCL but at a lower max voltage of 1.2V opposed to 3.3V.
    Without dead battery:

    With dead battery:



    The datasheet of the BQ doesn't seems to indicated anything concerning the I2C pins when not powered (PPHV power line is 0V), it should be a standard to be high Z.
    BQ datasheet: bq25792 (2).pdf

    What do you suggest to do ? Vin from connector (Vbus) is 5V.

    Thank you.

    Kindly,

    NA

  • 0 in reply to Nicolas Armogathe
    TI__Guru 70031 points

    Hello,

    The VIH minimum for both devices is 1.3V, so I suspect the communication is not working.  In the original design the dead-battery condition is always enable sink instead of safe mode.  Have you tried with always enable on to determine if applying VBUS/PPHV to the BQ device resolves the issue with loading from dead battery?   

    Alternatively, can you disconnect the I2C from the BQ device and see if the I2C lines go to LDO_3V3?

    Regards,

    Chris

  • 0 in reply to Chris Sterzik
    Prodigy 120 points

    Hello Chris, 

    You were right about checking all the devices on this I2C bus. There was another unpowered device connected that was pulling the lines low; that IC is located elsewhere in my schematics and wasn't on the page I shared.

    SafeMode is working correctly and configures properly via the external flash. Also, the PD contracts are correct in both dead battery mode and normal operation. Thanks for your help!

    Kindly,

    NA