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SND9039 Cherry Trail power up problem

user021864
Intellectual 2145 points

Hi, 

My customer have problem during power up. 

This happens during fast turning on and off the PMIC. 

condition: connect and disconnect the 5V adapter to the PMIC will cause problem for power up. 

Originally, power up automatically after adapter is connected, but under this operation, it will need to press power bottom to start up. 

What i want to know is why this happens and how to solve. 

Now i am asking customer to check if we are in to PMIC off before the adapter is connect again and see where does the sequence stop during cold boot. 

Please help if you have further comments. 

thank you.

  • 0
    TI__Expert 6330 points
    Hi,

    I have notified our expert regarding this topic. Please expect a response by 9/14/18.

    Thanks,
    Aaron
  • 0 in reply to Aaron Goodson
    TI__Expert 4940 points
    Hello,

    Seems to me that the insertion of the 5V adaptor is not clean. If after reaching the Vbat>Vthreshold, Vbat drops PMIC will set the low voltage fault and stop the power up sequence. PMIC will be in Mechanical off state, the only way to get out of this state is by the power button.
    My recommendation is to check the input to the PMIC when adapter is inserted and to add enough decoupling to eliminate VIN bouncing.
    For further assistance I'll need scope captures of the power on sequence.
    Let me know if I answer your current question

    Regards,
    Costin