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TPS659037x ----- the current path SMPS8 output to LDOLN_OUT output

Michi Yama
Guru 10030 points
Other Parts Discussed in Thread: AM5728

Hi,

I have one question regarding TPS659037x with AM5728 processor.

My customer has one issue "unexpeced current path" with TPS659037x.

Please see the below.

[Background]

* When power up, LDOLN_OUT output rise the voltage level faster than basic timing.

* From waveform, customer suspects there is SPMS8 output to LDOLN_OUT current path. Please see the below waveform.

* Customer does not use both voltages in one block. So customer think this current path occurs in AM5728.[  

[Question]

1.is it no problem the above situation when power-up? If it can be allowed the above situation, how voltage is allowed?

2. If the above situation is problem, please let me know the countermeasure.

I appreciate your quick reply.

Best regards,

Michi

  • 0
    TI__Genius 16410 points
    Yama-san,

    I discussed with the AM572x team. This small voltage on LDOLN_OUT will not cause any issue. There isn't a specific threshold voltage between "allowed" and "not allowed". In this case, the design team did some analysis to determine that the ~100mV in this case will not cause a problem.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Guru 10030 points
    Dear　Karl-san,

    Thank you for your quick reply. It is very helpful for me.

    I understand that " ~100mV " in this case will not cause a problem.
    If the voltage is 200mV, is it problem? How about 300mV?
    I would like to know the maximum voltage that is allowlled as AM572x.

    I appreciate your quick reply.

    Best regards,
    Michi
  • 0 in reply to Michi Yama
    TI__Genius 16410 points
    Hello Yama-san,

    As I mentioned before, we don't know a maximum voltage. In this case, the processor design team said 100mV will not cause an issue. I think to determine a maximum voltage, they will need to do a different sort of analysis, which I'm not sure is possible. I can't really help with this, since this is a processor requirement and not a PMIC requirement.

    I think the TI FAE for your customer is already in contact with the Sitara processor team to determine if this is acceptable. In case you have more questions, please contact me by e-mail which you can find in my profile. I can connect you to the people to support your question.

    Regards,
    Karl