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BQ24725: BQ24725 connectivity and application

Tzachi Bear97
Intellectual 320 points
Part Number: BQ24725
Other Parts Discussed in Thread: BQ25710, BQ25890, BQ25898, BQ24610

hi 

we are planning to use the BQ24725 in our design in order to charge our battery

i have two questions  - 

1. how can i measure the battery voltage level? can my controller get this information via the I2C interface through the charger even when not charging?
this question is to provide the information required in order to perform a shut down when reaching a low voltage - but we need to get the voltage level

2. how do we connect the NTC pin coming from the battery as a protection? is there a connectivity for this in this charger? or do we need to build additional circuitry?

thanks

Tzachi 

  • 0
    TI__Mastermind 25800 points

    Hey Tzachi,

    For 1) This charge controller cannot measure the battery voltage directly and report back to the host. 

    For 2) This charger does not have an NTC connection like some of our integrated chargers. You would need some external circuitry to add battery temperature-based protection.

    This controller is traditionally paired with a battery fuel gauge in order to monitor the state of charge, the charging current, cell voltage, and battery temperature, at which point the host makes decisions on that information.

    I can also recommend the BQ25710 which does include an integrated ADC which can help with reading the battery voltage (1). However, you will still have to implement an external circuit to monitor battery NTC temperature.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 320 points

    Thank you Joel

    can you recommend a charger that has the NTC, voltage level reading and has an automatic power selection between the adapter and battery to the system?
    thanks

    Tzachi

  • 0 in reply to Tzachi Bear97
    TI__Mastermind 25800 points

    Hey Tzachi,

    If you are using a single-cell battery, I would recommend using something like the BQ25890 (QFN) or the BQ25898 (WCSP). These are integrated, have a TS pin for temperature monitoring, and have an integrated 7bit ADC for voltage and charge monitoring.

    However, if you are looking for a multi-cell solution, we do not have a device that can do both NTC monitoring AND voltage level reading; however, you can easily voltage divide the battery voltage and feed that to your controller's integrated ADC or an external ADC. In that case, I would recommend the BQ24610, which is a standalone charger that has a TS pin to connect a battery thermistor. It also a power path selector between the input and the battery. And the battery voltage is already divided down to feed the VFB voltage.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 320 points

    thank you Joel

    have a great weekend