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Original question:

TPS61200 draws to much current with no load

TPS61200: TPS61200 draws too much current using the UVLO-function

user5833199
Prodigy 30 points
Part Number: TPS61200
Hi everybody,
i am using the TPS61200 in an application with a low power energy source (less than 1 mA) that is charging a small super capacitor. After charging the capacitor to 0.7 V i want the TPS61200 to power a circuit with 2 V for a short period of time. I tried using the UVLO-function to power the circuit after the super capacitor reaches the desired voltage, but found that the device draws up to 30 mA in the charging process (even with no load). That is more than the device consumes when operating with open load while supplying the 2 V output voltage.
This way the super capacitor will never reach the desired 0.7 V (since the energy source can´t supply 30 mA) and i will have to use additional parts to set the EN to LOW until the super capacitor is charged.
Jan Greitens
  • 0
    TI__Guru 68495 points
    Hi user5833199,

    The engineer who is supporting this device is currently on vacation, and he will answer your question next week. By the way, what is your source that can only supply <30mA?

    Thanks,
    Youhao
  • 0
    TI__Mastermind 46905 points
    Hi Jan,

    Even the voltage in the UVLO pin is lower than the internal reference, the device just shuts down the VOUT. the device still switches to keep the voltage at VAUX. the power consumption in the period is actually not small. but the input current will depend on the input voltage level.

    what is input voltage when observe the 30mA input current
  • 0 in reply to Youhao Xi
    Prodigy 30 points

    We want to detect water by letting it create a primary cell. Therefore the current of that primary cell is quite low.

    I measured the 30mA input current at a voltage of 0.45V. When the voltage reaches 0.65V the input current has dropped to approximatley 2mA. After reaching the desired 0.7V and the VOUT is at 2V the input current even drops below 1mA if there is no load. So i was wondering if there there might be a latch-up effect inside the controler like they mentioned in the other question.


    Best regards Jan

  • 0 in reply to user5833199
    TI__Mastermind 46905 points
    Hi Jan,

    I observe similar behavior in the EVM. the input current is 30mA if the input voltage is 0.3V and decrease 2mA at VIN=0.7.
    I think the behavior is caused by the efficiency of device at very low input voltage if the UVLO is triggered and the power loss of the internal circuit, it is not caused by the latch-up.

    currently, we don't have a good solution to improve this behavior.
  • 0 in reply to Jasper Li
    Prodigy 30 points
    Hi Li,

    thanks for the effort. In that case i will use an additional voltage detection circuit to set EN low until the capacitor reaches 0.7V.

    Best Regards Jan