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BQ24092: Reducing the total charging time

Parth Dholakiya
Expert 1245 points
Part Number: BQ24092

Hi,

We are using BQ24092 charger IC in our product to charge a 3.7V /300mAh LiPo battery. The average Load of our system is 100 mA. We have tested charging cycle with and without load.We observed that it takes around 1hr 30min to charge up to 4.19V where CHG pin goes high.It charges quickly up to 3.7V but from 3.7 to 4.19 it takes more than an hr. We have set Iset current as 450 mA and PRE-TERM pin is pull down to ground with 2 k  resistor. 

We want to design the charging circuit such that it should take around an hr to fully charge the battery with load of 100 mA ,w hen charged from the USB port of the PC.It will be great if you can help us on this .

Thanks in advance.

  • 0
    TI__Guru 68686 points
    The problem may be the ISET2 pin, if it is Floating this input / output current is limited to 100mA.
    Try grounding and re-test.
  • 0 in reply to Bill Johns
    Expert 1245 points

    Hi,

    We have connected ISET2 pin to ground so that we have ISET current same as that we have calculated by setting RSET resistor. We tried testing ISET pin by pulling it up to Vbat believing we can get maximum of 500mA as ISET current but in both these case we are facing the same issue i.e battery takes more time to charge.

    I will provide you with the information of all resistors that we have connected to different pins:                                                                                                     

    RSET = 1.5K

    PRET-TERM = 4.7K

    ISET2 pulled down to ground

    Please help me out to fix this issue.

    Thank You.

    Regards

    Vidula 

  • 0 in reply to Parth Dholakiya
    TI__Guru 68686 points
    Hello
    RSET=1.5k (R34) the fast charge current will be 360mA
    PRET-TERM=4.7k (R35) the termination current will be 4.25% or 15mA.

    With the average load on out of 100mA it may be difficult for the charge to reach termination, current will need to decrease below 15mA.
    Increasing the termination current will reduce charge time 10% is typical but can be higher, some impact on battery capacity.

    Max fast charge current to the battery will depend on the recommendations from battery manufacture. Typically it is 1C which would be 300mA for a 300mAh battery. Charge time can be decreased by increasing fast charge current, check with battery manufacture