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BQ77915: How to select RIN value for designing BMS Circuitry required specifications

prashanth reddy
Prodigy 30 points
Part Number: BQ77915

Hello,

I am trying to designing the BMS using BQ77915

Here the question is i am unable selecting the RIN value

Can you give suggestion for selecting the RIN value and what is the relation betwen RBL and RIN value

Thanks 

Prashanth

  • 0
    TI__Expert 7455 points

    Prashanth,

    Typically, the value for Rin is 1k Ohm.

    The value can be changed if you wish to adjust the cell balance current. If this is the case, refer to section 10.2.2.1 of the datasheet. This section walks through a design example for an 18V Li-ion battery pack using 4.2V cells. In this example, cell balancing is required, so the CBI pin must first be connected to VSS. Then, the value of Rin is determined. The taper current in this scenario is 250mA, and 10% of that is 25mA. In this scenario, these cells would require a 164 Ohm resistance to achieve that 25mA current. This resistance is composed of 1 Rbal and 2 Rin. The typical value for Rbal is 12 Ohms, so each Rin would need to be 75 Ohm in this scenario.