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BQ24725A: BQ24725A Application problems

2018
Expert 2630 points
Part Number: BQ24725A

1.Is there any other way to judge if the charging process is over? In addition to inquiring about the output voltage (i.e. inquiring charging current), BQ24725A has other ways to determine whether the charging process has ended.

2.What scenarios are Watch dogs used inside the chip?

3.charge current sensor Can it exceed 20mΩ?

  • 0
    TI__Expert 5330 points

    1.  It is recommended that the battery that is charged by the BQ24725A would have a gas gauge that can be used for cell balancing and charge termination. 

    2.  The purpose of the watch dog is to guarantee that BQ24725A doesn't overcharge the battery due to loss of communication with the uC controlling it.  As mentioned previously, it is generally the case that this uC would also be communicating with a gauge device on the battery pack in order to determine the proper time to terminate charging.  If something were to cause the uC to be unable to communicate with the BQ24725A, then it might not terminate at the proper time.  So the watchdog requires the uC to "check in" with BQ24725A periodically to ensure that communication is active.  If the uC fails to check in, then BQ24725A will reset.

    3.  If the current sensing resistor value is too high, it may trigger an over current protection threshold because the current ripple voltage is too high. In such a case, either a higher inductance value or a lower current sensing resistor value should be used to limit the current ripple voltage level.  A current sensing resistor value no more than 20mΩ is suggested.

     

    Regards,

    Steve