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bq24630: OK to increase precharge current to 250mA, using 5mOhm current sense resistor?

John M
Expert 2135 points
Other Parts Discussed in Thread: BQ24630

Hello,

We'd like to increase the bq24630 nominal precharge current value from 125mA to 250mA using a 5 milliohm current sense resistor. Other than a decrease in charging current accuracy are there any other potential problems with doing this?

If our charge current is set to 3A, it appears that the termination current threshold would remain at 300mA irregardless of current sense resistor value. Is this correct?

Thank you!

JohnM

  • 0
    TI__Expert 5565 points

    John,

    Both the charge current and the termination current are a function of the sense resistor (referred to as Rsr in equations 2 and 4 in the datasheet). If you would like to only change the precharge current, then along with changing the sense resistor, you you will have to change the resistor divider values on ISET1 and ISET2 such that your charge current and termination current remain the same.

    Other than worse current regulation accuracy, there are no other concerns.

  • 0 in reply to Smriti B
    Expert 2135 points
    Thank you Smriti!
    I had forgotten to mention that we had already calculated the new ISET resistor values. Very glad to hear that we can increase the precharge current value. It appears that we will go from about +/-3-4% accuracy during a 3A charge to roughly +/-10% accuracy using a 5mOhm resistor. C/10 termination current accuracy will drop from about 30% to 40%. These changes won't be a big problem.

    Thanks again,
    JohnM