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About discharge current of 10A support product

Tsukui Yusuke
Guru 21930 points
Other Parts Discussed in Thread: BQ25616, BQ24073, BQ24170, BQ24616, BQ25606, BQ24172

Hi,

I am looking for a product that supports a discharge current of 10A.

The required specifications are listed below.
What device does TI recommend?

・Stand alone(RC setting)
・Battery discharge current 10A(max 20A battery)
・1cell Li-ion
・Charge voltage : 4.2V
・Charge current : 1.25A
・VBUS(Vin) : 5V AC adapter 
　(Vbus line will be cut during discharge)

Regards,
Yusuke

  • 0
    TI__Guru**** 166996 points

    Hi Yusuke,

    I assume you want a device with NVDC power path and integrated BATFET.  If so, I am not aware of such a device.  I suggest attaching the load directly to the battery.  Your current is low enough that you could use a linear charger like BQ24073 family or BQ25616, both of which have powerpath but you cannot use it because their BATFETs cannot discharge 10A.  If you know in advance when discharge occurs, you could place an external battery FET, with lower RDSon, in parallel with the internal battery FET and then turn on the external battery FET when you disconnect the VBUS line.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Guru 21930 points

    Hello Jeff,

    Thank you for your kind response.

    Based on your advice, Selected bq24170 and bq24616.
    However, when operating on 1cell Li-ion battery only(3~4.2V), the device is expected to be in the OFF state.
    Is my understanding correct?
    Is there anything I should be careful about when discharging 10A?



    And  If the customer does not need NVDC power path and integrated BATFET,
    Is it possible to consider BQ25606 / BQ25616?




    Regards,
    Yusuke 



  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 166996 points

    Yusuke,

    When using the BQ24172 with system connected directly to battery and the charger is disabled (i.e. not powered), I see no issue with the charger being damaged during discharged. 

    When using BQ256x6, you cannot discharge 10A through the internal BATFET.  You will have to either connect the load directly to BAT or connect the load to SYS with an external FET having lower Rdson than internal BATFET, between BAT and SYS.  This external BATFET would be turned on for the discharge event. The charger's internal BATFET would carry some of the current but most of the current would go through the external BATFET.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Guru 21930 points

    Hello Jeff,

    Thank you for your advice.
    I want to confirm one last thing.
    >You will have to either connect the load directly to BAT or connect the load to SYS with an external FET having lower Rdson than internal BATFET, between BAT and SYS. 
    Are there any precautions or concerns when using with ”connect the load directly to BAT”?

    I am considering the following circuit.
    It is the understanding that when 10A is discharged, the charging current and the battery discharge are summed and output.
    Could you give us your advice on the expected behavior at this time?



    Regards,
    Yusuke


  • 0 in reply to Tsukui Yusuke
    TI__Guru**** 166996 points

    Hi Yusuke,

    The BQ25606 internal BATFET is only capable of supplying 6A continuous discharge current.  The buck converter is only capable of supplying 3A maximum output current total = charge + system current, assuming the input power is high enough to allow this.  In the early post, you mentioned that the input adapter would be removed when 10A discharge occurs.  So, I suggest that you add an external FET between SYS and BAT to provide the majority of the 10A discharge current and turn it on at the same time that you turn off the input supply.  That FET needs to have RDSon lower than the internal BATFET's RDSon.

    Regards,

    Jeff