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TPS61089: TPS61089 BOOST CONVERTER

sudarshana adiga
Prodigy 90 points
Part Number: TPS61089
Other Parts Discussed in Thread: PMP9779, TPS61022

Hi,

i have an issue with TPS61089 device. Getting 3.8v o/p when EN is low and 5V o/p when EN is high. I/p is 4.2V and o/p is 5v. 

  • 0
    TI__Mastermind 40080 points

    Dear Sir,

    When EN is low, TPS61089 disabled, Vo is connected to the Vin through the upper side body diode. So Vo=Vin-0.4V (0.4V is the body diode voltage drop);

    When EN is high, TPS61089 enabled, Vo=5V target.

    So it works normally.

  • 0 in reply to Helen chen
    Prodigy 90 points

    Hi sir,

    As per the datasheet pin no 7 (EN) is logic input, logic high enables the device and logic low disables the device and turns it into shutdown mode. Any other option to disable the output during EN = LOW.

  • 0 in reply to sudarshana adiga
    TI__Mastermind 40080 points

    Dear Sir,

    You need to add a disconnect MOSFET(or load switch) at the output side.  You can refer to the TI design PMP9779 for a reference.

    So you can also choose a TI part with load disconnect function, like TPS61022.

  • 0 in reply to Helen chen
    Prodigy 190 points

    I too was caught/surprised by this behavior which you are calling "normal".

    One would conventionally expect the output to be 0V from a power supply that is not enabled.

    Furthermore, we are observing with the TPS61089-742 EVM that the regulation starts to collapse for load current above about 400 mA.

    We would have expected it to support up to 2A. Is that not correct?

  • 0 in reply to LL
    TI__Mastermind 40080 points

    Dear Sir,

    For the boost converter, some boost has load disconnect function, some don't have load disconnect function.  For the TPS61089, if you check the block diagram in the datasheet, you can see the the input is connect to the output through a body diode.

    The TPS61089 can support 12Vout/2A when Vin=5V