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TPS63061: TPS63061 Vout changed when load changed

Part Number: TPS63061

HI ,

In my case ,Vin = 5V±0.25V,Vout = 5V.The Problem is when Iload = 250mA to 330mA,Vout = 5.15V to 5V.Conversely,When Iload = 330mA to 250mA,Vout = 5V to 5.15V.

About 30% ICs have such problem. And this problem exists in different batches.Such AS QUK TI 79F SD9Z、QUK TI 79F SE92、QUK TI 79K AJ4K、QUK TI 7AK C04F.

SCH as follow.

  • Hi Xingkun,

    Could you please verify that you are measuring the output voltage on the output capacitor, and that you are not including the voltage drop on the output wires.

    Please also check if the device changes power mode. You connected PS pin to GND, so the device will automatically change the power mode depending on the load current. For small load currents the device will work in PFM mode, with slightly higher output voltage and ripple. You can check the power mode by looking at the output voltage ripple. In PFM mode the ripple will be typically 20 mVpp while in PWM mode it will be a few mVpp. Alternatively, you can also try connecting PS pin to VIN and see if the output voltage will change with the load.

    Best regards,
    Milos
  • Hi Milos,

    Many thanks for the quick response. You are very professional and your answer is always very useful.

    I was able to take a few measurements, The result is the same as what you judged-the device changes power mode.

    But I also have a question, the datasheet tell us if PS pin was connected to GND,The device enters power save mode when the

    average inductor current falls to a level lower than approximately 100 mA. But In my design, the minimum load current is 250mA.

    The TPS63061 can't enters power save mode .As shown in Figure.

    Best regards,

    Xingkun

  • Hi Xingkun,

    That is strange, at Iout=250 mA the device should operate in forced PWM mode. Could you please double-check if the lower output current is really 250 mA and not maybe 25 mA? And also confirm that it really operates in PFM mode by looking at the switch node (L1 or L2) with a scope?

    Best regards,
    Milos
  • Hi Milos,

    Many thanks for the quick response. I was able to take a few measurements again . I will show you .

    1、The diagram bellow  shows power rail in my design.

    2、This picture was shown DC power supply  .

    3、This picture was shown waveform of L1  which load current was 250mA.

    4、This picture was shown waveform of L1  which load current was 330mA.

    Judged from picture 3 and picture 4 , the operation mode of TPS63061 indeed changed .

  • Hi Milos,

    Do you have any idea about my problem? I urgently need to solve this problem.Please reply to me as soon as possible.

    Thanks,

    Best regards,

    Xingkun

  • Hello Xingkun,

    have you checked if the phenomenon follows the unit, when you do a swap test?

    You say, that 30% of your units from different batches show this. That could lead to a solder issue. Could you check if the PGND power pad is connected?

    regards,

    Julian

  • Hello Xingkun,

    we haven't heard back from you. I am closing this thread. Please post back or open a new thread if you need further help.

    Regards,

    Julian