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BQ25898: Max Battery charging current in Standalone mode

Rejeesh Raj
Intellectual 330 points
Part Number: BQ25898
Other Parts Discussed in Thread: BQ25606

HI,

We wish to use the part Bq25898 in one of our designs. Our design utilises 3000mAH battery capacity.

We are planning to use BQ25898 as a battery charger; and it will be used in standalone mode.

If BQ25898 is used in standalone mode, is it possible to achieve battery charging current higher than 2A?

What will be the default output of REGN of BQ25898 if I connect VBUS to 12VDC input?

Please suggest a battery charger (supporting standalone mode) which can deliver higher charging current to battery along with keeping all the features BQ25898.

Thanks

Rejeesh S Raj

  • 0
    TI__Expert 8230 points

    Hello Rejeesh,

    Rejeesh Raj said:
    is it possible to achieve battery charging current higher than 2A

    The bq25898's default charge current is 2.048A as seen on section 6 of the 898 datasheet. If you require higher charge currents than 2A in standalone, I2C communcation will be needed. REGN with 12V input should be ~6V.

    I suggest reviewing the bq25606. It is a power-path standalone charger than can provide up to 3A, you can set the charge current using an external resistor. This device also supports high voltage input.

  • 0 in reply to Fernando Lopez
    Intellectual 330 points
    Hello Fernando,
    We set the battery charging current to the peak level (3A) using a micro controller (using I2C communication with Bq25898). I like to know the recommended input voltage (at VBUS) for 3A charging current. My source, which is planned to deliver power at VBUS (a wall mount charger) is capable of provinding 5V, and morethan 3A. Please let me know for this device expect more input voltage (ie >5V) for above mentioned charging current?
    Thanks
    Rejeesh S Raj
  • 0 in reply to Rejeesh Raj
    TI__Expert 8230 points

    Hello Rejeesh,

    Typically for 3A or higher charging applications we see VBUS = 9V primarily due to the increase in efficiency at 9V vs. 5V input at high charge currents. 

  • 0 in reply to Fernando Lopez
    Intellectual 330 points

    Hello Fernando,

    Thanks for the reply. I need a clarification in the same device ie Bq25898.

    If I keep the "Charge Enable pin" (active low) at high logic, I expect that the charging circitry will be OFF.

    At the above instance the DC-DC converter output from VBUS to SYS will be disabled.

    But at this time what is the condition of BATFET (Q4)?

    Is it possible to  get the Battery voltage at SYS, when the charger is disabled?  

    Thanks

    Rejeesh S Raj

  • 0 in reply to Rejeesh Raj
    TI__Expert 8230 points

    Hello Rejeesh,

    If charging is disabled and there is a system load present, the device will enter supplement mode and discharge the battery through the BATFET. Unless there is an over-current protection event or the host forces the BATFET to turn off via I2C, the battery voltage should be seen at SYS to supply the system's power.