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BQ25713: Questions on new project??

Steve Wenner
Genius 3190 points
Part Number: BQ25713
Other Parts Discussed in Thread: BQ25790

Good afternoon....

I need a part that charges and monitors LiFePO chemistry but without the USB stuff.  Can I use this part in such an application? (It appears so)

Secondly if the above is true.  The bus I am working with ONLY has I2C and GPIO available.  It appears that IADPT, IBAT and PSYS are analog output signals.  Can I get IADPT, IBAT and PSYS information over the I2C bus with a query after using PROCHOT to interrupt my microprocessor?

Thank you

Steve 

  • 0
    TI__Mastermind 24075 points

    Hi Steve,

      PROCHOT is a function used to throttle the CPU in the system. Usually if not in notebook applications its not a huge factor. Do you need this feature? It can be disabled if not being used. Input current and charge current can be monitored through the ADC of the charger IC.

    You can use this for LiFePo. If looking for an integrated solution you can check out BQ25790 as well.

  • 0 in reply to Kedar Manishankar
    Genius 3190 points

    Hi Kedar....

    I am putting a bid proposal together for railway application.  No USB needed.  This is an industrial application with I2C feeding a backplane PC/104 style computer.  I only have available to me (from a backplane) I2C and some digital I/O, NO analog.   We would like to do as much battery monitoring as we can and with a single chip solution.  The chemistry is LiFePO and we would like a fast charge rate of 6A.  This pretty much limits the chip selection real quick.  If I am reading your response correctly it sounds as if the charge and input current are available over the I2C bus.  Is this correct? 

    Are any monitoring voltages available over the I2C bus? Temperature?

  • 0 in reply to Steve Wenner
    TI__Mastermind 24075 points

    Hi STeve,

      Yes, setting charge current/input current limit and charge regulation voltage is over the I2C bus. Input current is a function of duty cycle so you can set a limit depending on adapter/input source current rating.

    This pin doesn't have a TS pin so external TS voltage of the battery pack should be done with your GPIO. Note that the this chip doesn't automatically handle termination, and this should be taken care of by the host/gauge in your system.

    You can read these through the ADC: Charge/discharge current, system and battery voltage, input current and CMPIN (we have an internal comparator available for use), VBUS and PSYS voltage readback.

  • 0 in reply to Kedar Manishankar
    Genius 3190 points

    Hi Kedar.

    Thank you for your response.  I still feel a little confused.  I would like to re-iterate what I "think" you are saying.  Please correct me if I say something wrong.

    We can set charge/input current and regulation voltage over I2C. 

    We can read charge/discharge current, system / battery voltage via ADC over I2C.

    No Temp Sensing is available.

    No battery termination is available.

    If I can sense battery voltage over I2C shouldn't can I then send an I2C command to the 25713 to open one of the switches in the main charge path? I do not want to add a guage chip.  I would like this to be a single chip solution.

    Thanks

    Steve

  • 0 in reply to Steve Wenner
    TI__Mastermind 24075 points

    Hi Steve,

       That is one option albeit inefficient. The ADC accuracy will not be as high at lower charge currents, but yes, once termination current is detected, then the host can disable charging. When battery is full or battery is not in good condition to charge, host terminates charge by setting REG0x00[0] to 1, or setting ChargeCurrent() to zero.

    Termination is based on 2 parameters, both output voltage and charge current, as during CV loop the output voltage is regulated while charge current tapers down. Once it tapers down to the termination current threshold, then the charger should be disabled.