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BQ25101 in TTDM mode operation potential issue (no battery and TS pin left open)

Other Parts Discussed in Thread: BQ25101
BQ25101 is working as expected as long as there is a battery attached.
However I am looking to be able to power the board through BQ25101 in TTDM mode ( no battery and TS left open).
The problem is that it seems that I can not get 40mA - 50mA from BQ25101 out, while having it powered with 5V and the ISET resistor is set for 184mA
I  measured the output voltage and it is as expected: 4.2V
Is it this operation mode supported by BQ25101? (5V input, 50mA output/4.2V, no battery and no TS resistor, TTDM)?
  • Cezar,

    I've got an EVM set up and do not have any issues getting the desired operation on the bq25101.

    I've set the charge current to about 185mA, set TS pin to float and added a resistive load to the OUT pin.  With about 70 Ohms, I read 58mA of input current.  

    The output is 4.2V.  If I float the output, the current drops to quiescent current.  Try with a resistive load before powering your system.  If that works, check your inrush current to see if that's showing up as a short on the BAT pin.

    I have powered under different sequences (no battery, 70 Ohms, TS floating then add VIN:  Add 70 Ohms after add VIN).  

    What does the VOUT pin do on the scope?

    Regards,

    Dick

  • Hi Dick,

    I'm replaying on behalf of Cezar.  It looks like our initial tests were incorrect due to them being run on a faulty PCBA.  It turns out our recent findings are in line with the data sheet and with your response.  thanks for looking into this.

    Mike

  • Mike, Cezar,

    Great news!  Thanks for letting us know.  If you have any further questions, please don't hesitate to use the forum.

    Regards,

    Dick