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TPS61200: High current draw (23mA) despite load of only 1mA

Sam Lane
Prodigy 30 points
Part Number: TPS61200

Tool/software:

I recently had a circuit manufactured based around the TPS61200, designed to boost the voltage of a single cell rechargeable AAA battery (1.2v) to 3.3v for use in powering a single low current LED.

I have set the output resistors to provide a voltage of 3.3v, which the device achieves successfully, and the UVLO resistors are set to cut out at less than 0.9v input.

The load on this regulator is <1mA, however I measure a load on the input of 23mA irrespective of the external load on the 3.3v side of the circuit. This is a lot higher than the quiescent current of the device, and I cannot reconcile this high value with the efficiencies stated in the datasheet.

Have I made a mistake with the schematic, or is this expected behaviour?

(Please note that I am using three resistors for the output regulation resistors to facilitate BOM consolidation.)

  • 0
    TI__Guru 65280 points

    Hello Sam,

    With the PS pin pulled high, the power save mode is disabled, so the part is permanently switching independent of the load. So higher current consumption is expected.

    3mA are necessary to supply the load as your output voltage is 3 times as high as the input voltage and if you are using a battery as source, it is possible that the input voltage is even a lot lower and therefore the input current increases in addition.

    But 23mA sounds like much too high. What is applied to VAUX? Any load?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 30 points

    VAUX is connected to a mosfet being used for reverse polarity protection as described in https://www.ti.com/lit/an/slva315/slva315.pdf Figure 6.

    What would the behavior be if PW was permanently pulled low?

  • 0 in reply to Sam Lane
    TI__Genius 13305 points

    Hi Sam，

    if PS is low, the device is working under PFM mode, efficiency is higher。 Could you measure the inductor current by the way ?

    Also have I guess the converter has fully start up. Could you measure the VAUX node waveform , make sure the NMOS is working in saturation zone.

    you could switch PS low to test the input current under steady state.