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TPS2121: Standby current vs Quiscent current : is the device suitable to manage the switchover between the main supply and the battery of an RTC?

Alessandro Taddei
Prodigy 85 points
Part Number: TPS2121

Tool/software:

Hi TI Team,

I've already used TPS2121 in other applications and now I'm selecting it to manage the switching between the main supply and the battery for supplying an RTC.

The priority power supply as you can Imagine is  the 3.3V one, and only when this voltage is not present the battery must be used to power the RTC which must be always ON.

Attached you can see the schematic.

Reading the datasheet, at point 7.5 If I understand correctly, the current absorbed by TPS2121 from the battery  when the main supply is present should be the standby Current of about 6 uA (Figure 7-4) , is this correct?

According to the datasheet I should never fall in the case of the higher quiscent current, because the output is always connected to the IC4 RTC, Is this correct?

Last question: when the only voltage present is the battery one and therefore the battery supplies IC4 RTC , which is the leakege current abosrbed by TPS2121 from the battery?

Thanks for your help,

Alessandro

  • 0
    TI__Guru* 79181 points

    Hi Alessandro,

    Please let me check and get back.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 85 points

    Hello Kunal,

    Any news on this open point?

    Thanks

    Alessandro

  • 0 in reply to Alessandro Taddei
    TI__Guru* 79181 points

    Hi ,

    Sorry for delay.

    Reading the datasheet, at point 7.5 If I understand correctly, the current absorbed by TPS2121 from the battery when the main supply is present should be the standby Current of about 6 uA (Figure 7-4) , is this correct ?

    Yes

    According to the datasheet I should never fall in the case of the higher quiscent current, because the output is always connected to the IC4 RTC, Is this correct?

    I did not understand higher quiescent current but the channel which is on that will show the quiescent current as per datasheet.

    Last question: when the only voltage present is the battery one and therefore the battery supplies IC4 RTC , which is the leakege current abosrbed by TPS2121 from the battery?

    So battery will have quiescent current from battery to gnd. 

    Regards 

    Kunal Goel