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BQ24133 - charge termination

Dice-K
Mastermind 7480 points
Other Parts Discussed in Thread: BQ24133

Hello,
I have two questions about BQ24133.

1.
Fast charge current is 1295mA(typ).
Rsr is 10mΩ.
Charge termination current is 130mA(typ).
Is charge termination current(min) 130mA * 0.6 = 78mA? (Vsrp-srn=2mV)
Or is it 120mA?
I read page-8 of the datasheet.
Note-3 "The minimum current is 120 mA on 10mΩ sense resistor."


2.
Because fast charge current is small(1295mA), is it better that I use a larger Rsr(e.g., 20m Ω)?
This purpose is to raise the precision of the charge termination current.

Regards,
Daisuke

  • 0
    TI__Expert 3160 points

    Daisuke,

    1. Charge termination will be 10% of your fast charge setting (130mA, typ). At VSRP-SRN=2mV the accuracy will be +/-40%.  
    2. You may go with a larger sense resistor to raise the precision; make sure you recalculate your ISET bias resistor accordingly. Also, keep in mind that the maximum VISET = 0.5V for the BQ24133 so with a 20mOhm resistor your maximum charge current will actually be limited to <1.25A.   If you need higher, you can change devices to the bq2417x family which have a higher current capability. 

    Thanks!

    Rachel