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TPS25750: USBC (sink only) does not work

Juliane Kraus
Prodigy 10 points
Part Number: TPS25750

Hello,

I designed a board as 15V USBC sink using TPS25750D.

Now after manufacturing the boards I am stuck on a problem. The USBC supply simply won't work.

According to this forum topic https://e2e.ti.com/support/interface-group/interface/f/interface-forum/988215/faq-tps25750-how-do-i-create-a-sink-only-usb-c-pd-port-to-replace-a-legacy-barrel-jack-connector I should connect PP5V to GND when using TPS25750 as sink only.

1.    Error description:

When the Eeprom is not programmed I get 5V on VBUS.

The moment I programmed the eeprom and plug in the USBC the 5V will turn off every ~750ms.

PPHV is never activated. I can measure about 200mV on those pins.

The used CCy pin will go up to ~1,6V (same as Eval board) and tries to negotiate the voltage. Shortly before the 5V supply is switched off, the voltage on CCy jumps to 4V.

  (CCy on my board)

2.    Differences between my Board and the evaluation module:

  • all GPIOs are tied to GND as described in the datasheet pin description.
  • PP5V is tied to GND as described in the forum entry.
  • VIN_3V3 is not present.
  • I am using a PD only USBC socket. It only has VBUS (2x), GND (2x) and the two CC pins. No data lines available.

 there must be a differemce which I am missing but I can't seem to figure out what it is.

3.    Tests I already did:

  1. Evalboard: Shorten PP5V to GND (same as on my board) à still works and I get 15V with the same bin-File.
  2. Evalboard: Shorten all GPIOs to GND (same as on my board) à still works and I get 15V.
  3. Evalboard: Remove the 3V3 supply jumper from VIN_3V3. à still works and I get 15V.
  4. My board: Track the I2C communication between TPS25750 and Eeprom. à the slopes look good and the data I can read on the scope is the same as in the bin-File.
  5. My board: voltage on CCy pin. See attached image. I do not understand why the voltage goes up to 4V.6.    My board: I tried a different USBC power supply.--> same problem.
  6. added more capacitance in VBUS (40µF instead of 20µF) --> no difference
  7. I tried different settings an bin-Files. 5V - 3A sink only; 15V 3A - sink only, 9V - 3A device --> always the same. It works on the evaluation board but not on mine
  8. compared startup on both boards (15V 3A sink only bin-File)

(Startup Evalboard)

(startup my board)

yellow: CCy

blue: PPHV

green: VBUS

Have you encountered this problem before and can help me solve it?

Thanks in advance.

  • 0
    TI__Mastermind 32531 points

    Juliane,

    How are the resistors on ADCIN1 and ADCIN2 configured on your board?

    The part looks like it may be going into an incorrect state.

    Based on what I see in your schematic, please remove the pull-up resistors to LDO_3V3 and LDO_1V5.  This will configure the TPS25750 into SafeMode with an I2C address of 0x21.  This will match the EVM and match your intended behavior.

    Regards,

    Chuck

  • 0
    Prodigy 10 points

    Hi Chuck,

    thanks for the reply.

    The pullups on ADC1 and 2 are not populated. I placedonly the pulldowns to GND.

    I found a similar topic saying it might be the interrupts and disabling them in advanced settings seems to fix the problem.

    Unfortunately, I do not fully understand how to set the sinking voltage and current in advance settings.

    1. I disabled all interrupst and GPIOs

    2. I set the number of sink PDOs to 1.

    3. I edited the Sink PDO 1 to say 3A 15V.

    4. I set the number of source PDOs to 0.

    When i write the bin-File to the Eeprom and plug in USBC I only get 5V. Something seems to be wrong with the settings but the customization Tool users guide does not really tell me how to use the advance settings.

  • 0 in reply to Juliane Kraus
    TI__Mastermind 32531 points

    Juliane,

    If you disable all of the GPIOs, then you should not have to disable the interrupts.  This is in fact and issue that we will be resolving with the next GUI release.

    We should not allow you to change PDO1 to any voltage other than 5V.  This is required to be allowed to be type C compliant.

    Try changing you number of sink PDOs to 2 and make the second PDO 15V/3A.  This should address you issue.

    Please try this settings change and let me know if this helps resolve your issue.

    I have taken a note that we need to improve our documentation of the advanced settings of the GUI.

    Regards,

    Chuck