• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 234 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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: Output voltage value is not getting set as per OSEL

Karthikeyan Subramanian
Prodigy 40 points
Part Number: TPS61094

We need your suggestions with respect to the observation we have while testing with TPS61094. Please find the Schematics and PCB layer pictures attached for reference.

When we supply 4.9V at the input, we observe 4.8V at the output, but not 3.8V as per the design requirement. 

The voltage across PC1 (SuperCap) is slowly rising and settles at 2.7V. But the output remains same at 4.8V. When we tried to remove input voltage, the output voltage goes down to 0V.

Thanks

Karthikeyan

TPS61094DSSR_SCH_LAYOUT.PDF

  • 0
    TI__Expert 5180 points

    Hi Karthikeyan,

    The sch seems basically ok to me. In auto buck/boost mode, if Vin is higher than OSEL voltage, the output voltage equals the input voltage which is 4.8 for your application. The output should be 3.8V when input voltage is lower than the setting boost regulation voltage. So "When we supply 4.9V at the input, we observe 4.8V at the output" is normal. Could you please check the Vout when input voltage is decreasing below target Vout? I think in this situation, the put put should be 3.8V.

    Best Regards,

    Eric Yue

  • 0 in reply to Eric Yue
    Prodigy 40 points

    Thanks Eric. Yes we checked the output to be 3.8V when the input is lower than that.

    But this is not our intended application. We require the constant output 3.8V when the input is higher, ie. 5V (Buck output) and when the input goes down, the output should be maintained at 3.8V, using the Supercap as the backup (Boost output). Please let us know whether this is possible with any other configuration of this Circuit.

    Thanks

    Karthijeyan

  • 0 in reply to Karthikeyan Subramanian
    TI__Expert 5180 points

    Hi Karthikeyan,

    If the load is heavy and input source cannot supply Vout, TPS61094 will enter Supplement mode which the bypass switch operates LDO and input and super cap supply output together. But if the input power source can support the output load, the output is always Vin. If this not meet your application, I think maybe one LDO or buck is needed to transfer 5V to 3.8V supply first. I can search for if there is anymore better methods, please leave several days. Thanks.

    Best Regards,

    Eric Yue

  • 0 in reply to Eric Yue
    TI__Expert 5180 points

    Hi Karthikeyan,

    Through my check, the most suitable approach is adding one LDO to transfer 5V to 3.8V supply first. You can select the LDO in TI.com as well. Sorry for the inconvenience.

    Best Regards,

    Eric Yue