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Original question:

BQ25970: How to calculate the resistance in bq25970 while fast charging

BQ25970: power dissipation in fast charge

Domenyko
Prodigy 10 points
Part Number: BQ25970
Other Parts Discussed in Thread: BQ25968

Dear Sir,

can you please provide me with more details on how to calculate the power dissipation during the fast charge? The datasheet of BQ25970 does not have any relevant info.

thanks,

Domenico

  • 0
    TI__Prodigy 430 points

    Hi, Domenico,

    In order to calculate the power dissipation, we can measure the input voltage, input current, output voltage, and output current whiling charging battery. The power dissipation is equal to input voltage*input current - out voltage*output current.

    Best,

    Zhiyong

  • 0 in reply to Zhiyong Xia
    Prodigy 10 points

    Hi Zhiyong,

    thanks, but I'm more interested to the Rds on of the FETs inside the BQ25970.

    I do not know If I can cosider the ones present in the BQ25968 because in the comparison table on page 4 of the Datasheet of BQ25968 the BQ25970 seems supporting 8A while the BQ25968 only 6A.

    best regards,

    Domenico

  • +1 in reply to Domenyko
    TI__Prodigy 430 points

    Hi, Domenico,

    Which application do you use BQ25970 at? Knowing the application background may help us better assist you. 

    The typical Rds-on values of FETs inside BQ25970 are almost the same as BQ25968 as shown in the figure below.

     

    The reason why BQ25970 can support 8A charging is because of the different protection mechanisms. 

    Best,

    Zhiyong