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bq1510x IOUT ~4mA

Sean Montgomery
Prodigy 20 points
Other Parts Discussed in Thread: BQ25101

Hi

I'm looking to incorporate the bq15101 into a future product that will use a very small Li Pol battery (~8mAh). To meet battery spec of 0.5C charge current, we would need to set the bq15101 charge current at ~4mA, but the datasheet suggests that the mimimum IOUT  is 10mA.

- Would it be possible to use this module with IOUT =4mA (RSET=36K)? 

- What concerns would you have about operation at a low IOUT value?

- With RSET=36K, are the optional RC values (2.7K, 10nF) specified in 9.2 in the datasheet the same recommended values? 

- Are there any additional considerations for the circuit we need implement to help stability? 

Thanks,

Sean

  • 0
    TI__Expert 7730 points
    Hello Sean,
    I suppose you meant bq2510x instead of bq1510x? The datasheet spec is the range that we have characterized, so the accuracy is also guaranteed. The charging current can be programmed to 4mA but the smaller the current, the worse the accuracy. However, we've seen similar accuracy at 5mA level compared with 10mA.

    With 4mA current, I definitely recommend using the same RC circuit to stabilize the signal. The value is the same.

    One other consideration you need to take is termination current. If you are using bq25101, the termination percentage is fixed at 10% of fast charging current, so it will be only 400uA which is below the minimum 1mA spec on the datasheet. Similarly, the accuracy will not be as good.

    Thanks,
    Wenjia
  • 0 in reply to Wenjia Liu
    Prodigy 20 points
    Indeed bq2510x, sorry for the typo.

    Do you expect the accuracy will fluctuate unit to unit or over time within a single unit?

    What termination current behavior would you expect if ISET=4mA on the bq25101?

    Thanks,
    Sean
  • 0 in reply to Sean Montgomery
    TI__Expert 7730 points
    Accuracy is not likely to change with the same unit but can vary from unit to unit. I think the actually termination current will be below 600uA for 4mA ISET.

    Thanks,
    Wenjia