• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 33 subscribers
  • Views 973 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65982 LDO_BMC is not enabled

Antony Lin
Genius 13480 points

Other Parts Discussed in Thread: TPS65982

Hi,

While customer tests the dead battery feature, sometimes the PD function is not normal.  Normally, VBUS will rises from 0V to 5V firstly, and them to 15V (contracted PDO) after adapter plug-in.

Now when the issue happen, they found VBUS only stays at 5V, and found LDO_BMC is not enabled at all.  (Other LDO from TPS65982 are normal.)

WHat could cause LDO_BMC failed to rise?  What can we check to further clarify this issue?

THanks!

Antony

  • 0
    TI__Mastermind 30310 points
    What is the capacitance on LDO_BMC?
    What is the voltage on VIN_3V3?
    What is the voltage on LDO_3V3?

    A waveform from an oscilloscope and the schematic will be needed to debug this issue.

    How many PCBs have you tested this on and how many have shown this behavior?
  • 0 in reply to Brian Berner
    TI__Genius 13480 points

    Hi Brian,

    Thanks for the comments. My update summzirza as below.

    • The capacitance on LDO_BMC is 2.2uF.
    • Some waveforms as shown below while PD adapter is plugged as dead battery mode.
    • Some signal voltage levels at this moment,
      • CC1=1.8V
      • CC2=0V
      • SPI_CLK is always low
      • SPI Flash input 3.3V is available
    • The issue is very difficult to duplicate and happens randonly.  It happens more than 1 PCB.

    What is your comments regarding what we can do for further calrification?

    Antony

  • 0 in reply to Antony Lin
    TI__Mastermind 30310 points
    Antony,

    You said SPI_CLK is always low. This indicates to me that the TPS65982 never attempted to read the SPI Flash during BOOT code.

    Is this a 2 Type-C Port ThunderBolt system?

    If so, are you reproducing the issues on the Primary TPS65982 (connected to the Flash) or the Secondary TPS65982 (Flash pins tied to GND, UART connected to Primary)?

    If you are testing the Primary TPS65982 or this is a 1 Type-C Port system, then please measure the voltage on SPI_MISO.

    If SPI_MISO is measure to be low during BOOT, then the TPS65982 will not attempt to access the SPI Flash IC.