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SND9039 reset problem

user021864
Intellectual 2145 points

Hi, 

I am using the cherry trail CPU and SND9039A2CTRSKR PMIC.

There is a problem that happened during operate with graphic card.

The BUCK5 of PMIC(VGG) will be different with graphic card.

When it's with graphic card, ourput will be in 0.75V to 0.85V.

When it's without the card, it will be stable at 0.85V

the reset happened during operate with graphic card, and won't happened if without graphic card.

is there suggestion for this issue? 

The other question is: how to adjust the output of buck 5?, is it through I2C from CPU?

Thank you.

  • 0
    TI__Expert 6330 points

    Hi,

    I have contacted our expert regarding this issue. Please expect a response by 5/29/18.

    Regards,

    Aaron

  • 0
    TI__Expert 4940 points
    Hi,

    Buck5 output voltage range is 0.4V to 1.1V, the CPU sets Buck5 Vout through I2C.
    The registers associated with Buck5 Vout:
    -reg_29hex sets Buck5 Vout
    -reg_2Ahex sets Buck5 Vout after stand-by
    -reg_2Bhex sets Buck5 Vout during stand-by
    Seems to me CPU has set different values in the above registers. My suggestion is to check reg29/2A/2B values.

    Regards,
    Costin
  • 0 in reply to Costin Cazana
    Prodigy 60 points
    Hi Costin

    Thanks for your reply.
    We have the 2% fail rate with using the cherry trail CPU and SND9039A2CTRSKR PMIC.
    When system get into WIN10 desktop and idle for a while, then it will auto reboot randomly.
    The symptom only occur in light load just like idle in desktop. Heavy load like play video and burn-in test will not happen the symptom.
    We find that if the system in WIN10 safe mode or without graphic driver, the symptom will not happen.
    We doubt it is related to VGG(buck 5) of PMIC, and try to set buck 5 from auto-mode to forced PWM mode by BIOS.
    The symptom will not happen with this setting.
    What is the different between auto-mode and forced PWM mode?
    Could we change design to PWM mode only?
    Thanks.
  • 0 in reply to Costin Cazana
    Prodigy 60 points

    Hi Costin

    We have 2% fail rate of this auto reboot issue.

    What conditon may cause this symptom?

    We found that the symptom will not happen in WIN10 safe mode and without graphic driver.

    It will only happen in light load like idle in desktop, and heavy load will not happen.

    We doubt it is related to VGG(buck 5) of PMIC, and try to set buck 5 from auto-mode to fixed PWM mode.

    By using this setting, the symptom will not happen anymore.

    Could we use only PWM mode? May this setting have side effect?

    Thanks for your reply.

  • 0 in reply to Keny Fang
    TI__Expert 4940 points
    Hi Kenny,

    Buck5 can be set to PWM mode only as long as Buck5 voltage is set higher than 600mV, the only side effect is slightly lower efficiency.

    In auto mode PMIC detects the load and set PFM for light load to improve efficiency.
    When reset happens what do you get in the status registers?

    Regards,
    Costin
  • 0 in reply to Costin Cazana
    Prodigy 60 points

    Hi Costin,


    Thanks for your reply. I am colleague of Keny.

    We checked with BIOS team, they didn't found the code which is about modifying Buck5 setting, that's mean Buck5 should be keep default register setting.

    So, we  like to know,

    1. Is the any possible reason about our symptom? (System will be reset in idle if Buck5 set as Auto-mode, PWM mode is okay)

    2. We noticed that the output voltage level of Buck5 in Auto-mode is lower than PWM mode during system idle, is that normal?

    3. Is there a tool in windows that we can monitor SND9039's register in real time?

    Thanks

    Nick

  • 0 in reply to nick lin
    TI__Expert 4940 points
    Hi Nick,

    1. The reset is generated by the SOC not the PMIC, it will be good to find out what type of reset by reading status register 12hex
    PFM has couple of millivolts higher ripple vs PWM but this should not affect the SOC, if possible scope check Buck5 Vout in Auto and forced PWM.
    2. Couple of millivolts lower voltage in PWM is normal if Buck5 Vout meets spec accuracy
    3. I'm not familiar with windows tools, my suggestion is to check first in real time PMIC input control signals and reg 11hex to figure out how reset has been generated.

    Regards,
    Costin