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TPS61099: Unexpected high output voltage in a load variation test

Part Number: TPS61099

Dear TI engineer,

   I'm testing the board uses TPS610993 to boost  from alkaline battery voltage to 3.0V. 

   I found an unexpected high voltage in load variation test.    I think TPS610993 is fixed output (3.0V).

  What is happening in my board?

  I tested same test  with TPS61099EVA-023. No high voltage.  3.6V fixed type is mounted in TPS61099EVA-023 .

  • 1. is this behavior found in several boards?
    2. could you make sure if you are using TPS610993, not TPS61099?

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Hi Jasper,

     Thank you for you quick response.

    >1. is this behavior found in several boards?

       I tested  2 boards. I found this behavior in both.

    >2. could you make sure if you are using TPS610993, not TPS61099?

      In static load, the output voltage is 3.0V.  I think it's TPS610993.
      Also I checked the device marking is 7911 17X.
         17X means TPS610993YFF. 
  • In reply to user5327650:

    does the device output 2.5V if the load is constant 62ohm? what happen if connect the 62ohm suddenly or remove the 62ohm, then measure the output voltage in stable load ( please do not use the NPN circuit)

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Result with resister 62 ohm and  mechanical sw.

    Output voltage in SW on : 1.7V

    Off: 3.0 V , 5.5V

  • In reply to user5327650:

    I will try if i can reproduce the issue with EVM.
    do you still see the issue if input voltage is 1.5V?

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    I tried  on TPS61099EVM-023 Board. I could not reproduce the same behavior.

    Followings are difference between my design and the EVM board.

          My board    TPS610993YFF  (3.0V  WCSP Package)

          EVM           TPS610995  (3.6V WSON Package)

  • In reply to user5327650:

    i will use EVM for WCSP package device to check this issue. could you increase the input current and check again.

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    In order to increase the input current, I chose to lower the impedance of the wiring. 

    shorten and thick

    It seemed that the probability of high voltage occurrence declined. 

  • In reply to user5327650:

    we see similar behavior but only trigger at VIN lower than 0.7V. could you please make sure the input voltage at the VIN pin always higher than 0.7V and check again? or you can try VIN=0.9V to check if this issue is still triggered.

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Jasper

    In my environment, its behavior in  Vin = 0.7V.   In the case Vin =0.9V, I can not find same behavior. 

    In my case, the load switching is done by manual.  It should be done by  test equipment like pulse generator.

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