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TPS65131: THE inductor is buzzing

user4973896
Expert 1555 points
Part Number: TPS65131
Other Parts Discussed in Thread: OPA2188, , TPS54331

Attachments are problem documents, schematics and PCBs.Looking forward to hearing from you！4571.Question.pdf

  • 0
    TI__Mastermind 24615 points

    Hi,

    I have notified our expert regarding this topic. Please expect a response by 9/9/19.

    Thanks,

    Shinya

  • 0 in reply to Shinya Morita
    Expert 1555 points

    it  might  to  be  too  late,can be earlier?

  • 0 in reply to Shinya Morita
    Expert 1555 points

    Now i find when i remove  F26,F25,which  is  supply to 7 OPA2188,the buzzing disappears.WHY?

  • 0 in reply to Shinya Morita
    Expert 1555 points

    I have modified a lot of parameters, but it won't work. Only when F26 and F25 are removed, there is no noise.why

  • 0 in reply to user4973896
    TI__Mastermind 18550 points

    Hello,

    You have a high conversion ratio assuming VCC input supply to TPS65131 is 3.3V and its output are +15V and -15V. In addition you have seven OPA2188 circuits connected to these supplies so load current will be significant. Can you tell what is load current of each OPA2188 on +15V and -15V supplies? I have a feeling that because of high conversion ratio and high load current, TPS65131 switches may be hitting current limit which is 1800mA for both boost and inverting converter (see datasheet). Another specification to check is saturation current for L2 and L3. Because switch current is high due to high conversions ration, the inductor may be getting saturated.

    Kind Regards,

    Liaqat

  • 0 in reply to Liaqat Khan
    Expert 1555 points

    I have tested it. When I disconnect the beads F25 and F26 (the two beads are used to power the OPA2188), the ±15V load is applied directly to the 7-channel OPA2188 with a ±15V regulator. The current is only about 7 mA. Then, when the beads F25 and F26 are disconnected, I directly connect the 2.35K resistor in the ±15V output of the TPS65131, that is, the load of 6~7mA, the inductor starts. Howl.

    And the input of TPS54331 and TPS65131 are 5V power supply, my power supply design is 5V to 3.3V, 5V to ±15V.The inductance is 4.7uH, how can such a small load current be saturated?

    I changed the corresponding resistor divider (R57~R60) resistor value and C63 and C66 capacitor value according to the TPS65131 output voltage ±10V setting in the chip datasheet, and tried to remove the input transistor Q1, 2,3 pins directly Short circuit, the No. 1 pin is suspended (that is, the 7th pin of the TPS65131 is suspended), all tried, but it is not OK.

    I need your help！

  • 0 in reply to user4973896
    TI__Mastermind 18550 points

    I did not know what that the load was in your application and that is why I wanted to check with you but I agree that with 7mA load, there should not be any issue with switch current limit or inductor saturation even at high conversion ratio of 15V/5V. I have reviewed rest of your design and don't see a reason for why the inductor should be buzzing. I am thinking that there may be some mechanical vibration in this particular inductor causing buzzing noise so the only thing I can suggest is to try a different inductor. The one we use in TI EVM design is Coilcraft part number XAL4030-472MEB.

    Kind Regards,

    Liaqat

        

  • 0 in reply to Liaqat Khan
    Expert 1555 points

    I have solved this problem.