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TPS706: TPS706 Iq is very high when the input voltage is lower than the fix output voltage

Billy Xu
Intellectual 460 points
Part Number: TPS706

Hi sir ,

I choose the TPS706  fixed output 3.6V for the MCU suppy.

when the input voltage higer than fix output voltage 3.6V , the TPS706 Iq is about 1.5uA .

But when the input voltage lower than fix output voltage 3.6, for example ,the input voltage is 3.5V ,the Iq is about 35uA .

Why the Iq is more than 33uA when the input voltage  is lower than LDO fix output  ? Thanks!

  • 0
    TI__Expert 4350 points
    Hi Aiming,

    When the TPS706 is in Dropout: Vin < Vout + Vdropout, the Iq will be higher. This is common with LDOs. Some datasheets will show a plot of the Iq in dropout. For example, see Figure 2 of TPS7B63 datasheet, showing higher Iq when the LDO is in dropout.
  • 0 in reply to Eric.Preiss
    Intellectual 460 points

    Hi Eric ,

    Thanks！

    Because our product is power supply by cell, we expect  to use 10 years.

    when Vin<Vout+Vdropout ,which component inside LDO consumed the additional power consumption?

    If we want to decrease the LDO Iq when Vin<Vout+Vdropout ,could you help to provide Ti other Chip solution ？

    Billy

  • 0 in reply to Billy Xu
    TI__Expert 4350 points
    Hi Billy,

    When the LDO is in dropout, the error amp has to drive the pass element fully on and this results in higher Iq. The amount of increase in Iq will vary by LDO. I do not know of an LDO that will have unchanged Iq in dropout.

    At 3.6 V for the MCU, the LDO will be in dropout for a large portion of the battery discharge.

    Could you use 3.3 V to power your MCU to avoid dropout? What is your battery cell chemistry?
  • 0 in reply to Eric.Preiss
    Intellectual 460 points

    Hi Eric，

    Thanks sir .

    The MCU is designed by our company ,it must use 3.6V for our apllication .

    The battery is Lion cell .