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TPS61094EVM-066: Not entering buck mode and charge supercap

Henrik Gade Hyldgaard
Prodigy 10 points
Part Number: TPS61094EVM-066
Other Parts Discussed in Thread: TPS61094

Hello

We are designing a iot device that normally use about 20-30uA, and about 200mA when transmitting NB-IOT LTE. Board is powered by 1x 8500mAH Li/SOCI2 battery(voltage about 3,4v)

we need the TPS61094 to output 3v3 to power the SIP mcu/Modem.

In this situation when the TPS61094 is running in auto buck boost mode, it will never go into buck mode and charge the super-capacitor, because Vin is almost the same as Vout target.

I was thinking of having the mcu to control the mode pin and set TPS61094 into forced buck mode to get the supercapacitor charged, and right before the device is transmitting I will put TPS61094 into auto buck boost mode, so battery is supplemented by the supercap. After transmitting is done I will put TPS61094 into forced buck mode again.

Will solution work, and is it the best power optimized solution?

Br

Henrik

  • 0
    TI__Guru 58641 points

    Hi Henrik,

    thank you for using the E2E forum.
    Due to a public holiday this Thursday and Friday the expert of this device is out of office.
    Please expect a reply beginning of next week.

    Best regards,
    Stefan

  • 0
    TI__Genius 12325 points

    Hi Henrik,

    Thanks for using e2e.

    TPS61094 can support that toggling mode pin when operating.

    But I am a little confused about your description below,

    Henrik Gade Hyldgaard said:
    and right before the device is transmitting I will put TPS61094 into auto buck boost mode, so battery is supplemented by the supercap

    The supplement mode means that the output current at VOUT pin is from both Vin and Supercap, the TPS61094 can't support that the Vin battery is charged by Supercap. So it can't work.

    May I know why do you need battery is supplemented by the supercap when transmitting?

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 10 points

    Hey

    if supercap not supplements Vout, when our device is transmitting, the battery voltage drops to much due to the high load from LTE modem.  

    my idea is to have the TPS61094 running in forced buck mode, to ensure that the supercap I charged. Just before LTE modem is transmitting, I would put TPS61094 into auto buck boost, so about is supplemented by supercap, to protect the battery from the high load.

  • 0 in reply to Henrik Gade Hyldgaard
    TI__Genius 12325 points

    Hi Henrik,

    Sounds like when transmitting, you want the supercap to boost to VOUT so that the battery voltage would not drop too much. Is this what you want?

    If my understanding is correct, it is ok by doing this for TPS61094. 

    Let me know if there is other question.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 10 points

    This is exactly what we want to achieve :-)

    thanks for your help :-)