This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS61094: SUP Voltage

Part Number: TPS61094

Customer is using 1550 rechargeable lithium battery with TPS61094 in Automatic Buck or Boost mode.  Nominal battery voltage is 4V.
Vin = 5.1V
Vout = 3.3V
Vchg = 4.1V
Ichg = 100 mA

It appears to me the the super cap voltage must be less than the Vout for the device to operate properly.  Is that correct?

Please advise.

Thanks,
Mark

  • Hi Mark,

    Let me check this on bench. I should have results on Monday.

    -Wenhao

  • Hi Mark,

    I have tested the case based on your condition and here is the process from start up to shutdown;

    Start-up

    Vin starts first, when it reaches to rising threshold (typ:1.7V), device turns on bypass FET so VIN is bypassed to VOUT directly. It is so called BYPASS mode;

    When VIN>VOUT_TARGET+100mV, device enters BUCK_ON mode and starts to charge supercap with programmed ICHG current;

    After supercap charges to VCHG, which is 4.1V, the device stops charge but still keep in BUCK_ON mode;

    Yellow: VIN, Blue: VOUT, Purple: SUP

    Shutdown:

    In the shutdown phase, when VIN drops to ~VOUT_TARGET+50mV, the device will quits BYPASS mode and then enters pass-through mode, which it shuts down bypass FET and fully turns on BOOST high side FET. In this phase, VOUT=VSUP;

    After SUP drops below VOUT_TARGET, the device then enters BOOST_ON mode and starts switching;

    When SUP drops below<0.7V and VOUT<VOUT_UVLO (1.6V typ), device enters shut down mode;

    Based on analysis, the device is able to operate appropriately when VCHG>VOUT_TARGET;

    Yellow: VIN, Blue: VOUT, Purple: SUP

    Let me know if you have more questions. Thanks!

    -Wenhao

  • Hi Wenhao,

    I'm looping in Tony Heglas, TI AFA, who will be handling this issue moving forward.

    We are waiting for feedback from the customer.

    Appreciate the extra effort on the testing.

    Regards,
    Mark