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TPS61170 48-V Phantom Power Application Cricuit Issues

Tetsuji Ono
Prodigy 40 points
Other Parts Discussed in Thread: TPS61170

In 48-V Phantom Power Application Cricuit of TPS61170,

the domain that the output oscillates abnormally exists from approximately +4.7V to +5.3V VIN.

I took the various measures including the review of the phase compensation, but am never recovered.

The abnormal oscillation did not come to happen at all when I separated VIN like attachment from the power line.

What is the abnormally oscillatory cause?

  • 0
    TI__Mastermind 40080 points

    Dear Sir,                                                                                                                                                                                                                          

    What is your input voltage? And what's your output voltage and maximum output current? On what kind of PCB board you did it? On the EVM board or on the board you lay it by yourself.                      

    BR, 

    Helen

  • 0 in reply to Helen chen
    Prodigy 40 points
    Dear Helen.
    Thank you for your Reply

    input voltage : +3.6V~+7.2V
    output voltage and maximum output current : +48V/40mA
    pc board : 6-layer Build-UP PCB,on the board lay it by myself

    Best Regards
  • 0 in reply to Tetsuji Ono
    TI__Mastermind 40080 points

    Hi,

    What about the compensation network parameter? 10nF+10K? And could you also paste the PCB layout, I need to know the GND connection.

    BR,

    Helen

  • 0 in reply to Helen chen
    Prodigy 40 points
    Hi.
    sorry. I cannot show the board layout.

    It is clear from the following phenomena that this problem is not caused by a PC board layout and phase compensation.

    Example
    Vin +3.6V - +5.0, +5.2-+7.2V: There is no problem.
    Vin +5.1V: An abnormal oscillation occurs.
    The abnormally oscillatory outbreak condition depends on only Vin.
    Do not depend on the condition of Iout (0mA - 40mA).
  • 0 in reply to Tetsuji Ono
    TI__Mastermind 40080 points

    Hi Tetsuji ,

    The problem you shown is still unstability problem, this can be caused by the loop ,  the layout, or the small input decoupling cap.  You can send the screenshot of the layout to me, my email address is helen-chen@ti.com. 

    1) I show a layout picture as below, I don't know whether your layout keep this rule. 

    2) make the wire from your input voltage source to the input of the TPS61170 as short as possible, enlarge the input capacitor, if the input wire is long or the source itself is not so stable, will also leads to stability problem. you can enlarge the input capacitor by  connecting a > 220uF electrolytic capacitor at the input of the TPS61170(very near the TPS61170 input side), this can decouple the input source from its load.

    3) if  it is not caused by the input source, you can change the compensation value, Rcomp=2k, Ccomp=220nF is more fit for this application.  And be carefull, as the 48V output voltage is very high, the 100V rating capacitor under 48V bias, its effect capacitance is only about half of the original value, please at least use two 4.7uF/100V rating cap at the output side.      

    Good luck to you,

    BR, Helen

  • 0 in reply to Helen chen
    TI__Mastermind 40080 points

    Sorry,

    There's something wrong with the E2E forum, I cannot attach the picture, what's  your email address, I can send it you by email.

    BR,

    Helen

  • 0 in reply to Helen chen
    Prodigy 40 points
    Hi Helen
    Thank you for your advise.
    I'll try to experiment again.

    Best regards.

    Tetsuji Ono e-mail : tetsuji.ono@teac.jp