• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 65 subscribers
  • Views 639 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.

TPS650864: TPS6508641 Power drop when power UP

baolong yan
Prodigy 40 points
Part Number: TPS650864

hi，

We design the PMU TPS6508641 circurt for Xilinx ZU3EG.

When we power up

the rail 0.85V drop 13ms a time.we change the ilim,but no effect.

this is the wave for 0.85V.

 

SW for 0.85V when voltage drop.

then this is the wave for 5V.

this is our schmatic.

TPS6508641.pdf

  • 0
    Prodigy 40 points

    Tips: The wave for 5V up is BUCK1_5V. not the LDO_5V.

  • 0
    TI__Expert 8730 points

    Hi,

    Looks like BUCK2 is turning off and turning on again. There is also large drop on 5V. Do you know the load current on 0.85V rail when BUCK2 shutdown happens. I have forwarded your request to application engineer supporting this device, but he is USA and he will provide you more feedback on this issue when he comes to office. In the meantime, if you send the inductor current/load current on 0.85V rail, that will be useful.

    Regards,

    Murthy

  • 0 in reply to Krishnamurthy Hegde
    Prodigy 40 points

    Sorry，currently I dont have a good tool  to measure the current on 0.85V。

    but I want to know What conditions can trigger the drop？

    Ilim，or else？

  • 0 in reply to baolong yan
    TI__Genius 17380 points

    Hi Baolong,

    It looks like a power fault is causing reset. My best recommendation would be to go down the power up sequence (Figure 6-11) and scope shot each rail. When you find a rail that either does not power up or powers up to the wrong voltage, that would indicate the issue.

    That said, I took a quick look at your schematic and I do not see that BUCK1_5V is connected to the V5ANA pin? If there is no V5ANA, then the BUCK3/4/5 will not work and would explain the power fault. Specifically, I would expect the sequence to reach BUCK5 (VCC_1V2) and then power fault. 

    If neither of the above provides a clear solution or next step, you can scope VSYS, VREF, LDO3P3, LDO5P0 to ensure they are all stable. If they are, I would recommend forcing CTL4 low after a power fault and then using an I2C master to read the power fault registers which can tell you why the PMIC shut down.

  • 0 in reply to Kevin LaRosa
    Prodigy 40 points

    Hi，kevin

    Thanks for your reply.And any rail fail of the power will cause the power reset help me.I connect the  V5ANA  to BUCK1_5V,and check up every rail,and use a new chip，the problem solved.

    And any rail fail will cause the power boot up again.

    Best regards,

    Arike from China