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  • TI Thinks Resolved

WEBENCH® Tools/TPS61256: 150mA output the output voltage drops?

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Replies: 6

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Part Number: TPS61256

Tool/software: WEBENCH® Design Tools

Hello,

My customer was considering using the TPS61256 component.

He also used WEBENCH for the design.  (Attached the Webecnh Report). He tried to simulate the circuit starting from the model provided by TI, both with PSpice and with TINA, but having reached a load of about 150mA the output voltage collapses.

Is customer mistaking something? Any comments?WBDesign12 SIT.pdf

  • Hi Antonio,

    I used webench to run the simulation with the condition of Vin 3-3.5V, Vo5V, 0.5A.

    Below are the simulation results:

    1. Steady state:

    2. Startup:

    The TPS61256 may not be able to startup into full load current. During startup, the resistive load must be at least 55Ohm.

    Can you let customer shows the simulation waveforms?

    Regards,
    Zack Liu
    Boost Converter Solution

  • In reply to Zack Liu:

    Hi Zack,

    I have simulated the circuit shown in the attached figure, and using Rout = 30ohm then Vout collapses to 3.3V instead of being 5V.

    Thank you for your support,

    Marco Cilmo

  • In reply to Marco Cilmo:

    Hi Marco,

    Like I said in the previous post, TPS61256 may not be able to startup into full load current. During startup, the resistive load must be at least 55Ohm.
    So in the EE, do you really need output connect with a 30 ohm load? Or just wait for the Vout ramping up to 5V, then the system starts to work?

    Regards,
    Zack Liu
    Boost Converter Solution

  • In reply to Zack Liu:

    Hi Zack,

    in my application, the load is complex, and I can't tell you how it behaves during the startup.

    Do you advise me to use another chip, or to implement a circuit to ramp the voltage up to 5V?

    Regards,

    Marco

  • In reply to Marco Cilmo:

    Hi Marco,

    Will the load systems start working as soon as voltage ramps up to 4V or 5V?
    If you're really sure the load draws current during the startup, TPS61253A has a 1.5A dc startup current limit, which is enough for your application. TINA simulation could be downloaded using WEBENCH.

    Regards,
    Zack Liu
    Boost Converter Solution

  • In reply to Zack Liu:

    Hi Zack,

    I read the datasheet of TPS61253A and I also simulated it, and this device complies with my requirements.

    Thanks a lot,

    Marco

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