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BQ25700A: Charging current 0A after restart

Atharv Rangnekar
Prodigy 41 points
Part Number: BQ25700A

Hello TI 

In my application host controller is turned on afterward by the user, first charger IC has turned on alone when the main powerline 

We require to charge the battery with 500mA current initially but we can see that Charge Current Register setting resets - 0x14: 0x0000. (when main supply is removed & battery is still present)

But we can see that other resisters which we are setting i.e... 0x15 (Charge Voltage Limit), 0x3D (Input voltage Limit), and other resisters like (0x12;0x09;0x30;0x31;0x32)  retain their value 

1) Is there any method so that the 0x14 resistor can retain its value after restart? 

2) Is there any way of connecting, with which we can power the IC from the battery so that it won't lose any register data? (Currently, we have followed Eval kit design)

Thanks 
Atharv 

  • 0
    TI__Mastermind 23655 points

    Hi Atharv,

    Atharv Rangnekar said:
    1) Is there any method so that the 0x14 resistor can retain its value after restart?

    If the device restart, register 0x14 will always reset to default (0x0000).

    Atharv Rangnekar said:
    2) Is there any way of connecting, with which we can power the IC from the battery so that it won't lose any register data? (Currently, we have followed Eval kit design)

    Please refer to datasheet section 8.3.1 Power-Up from Battery Without DC Source.

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 41 points

    Can we use the OTG feature in IC so that VBUS will always be powered, will it help to retain this 0x14 resistor? (We will ensure the battery is always connected and charged)

  • 0 in reply to Atharv Rangnekar
    TI__Mastermind 23655 points

    Hi Atharv,

    OTG feature does not retain the 0x14 register value.

    Any conditions for CHRG_OK low except ACOV will reset ChargeCurrent() to zero. -> i.e. adapter removal

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 41 points

    Hi Tommy 

    Want to explain our system

    Case 1: Adapter input of 15V connected, host Uc get power from adapter, we set (0x14) charger current register to 500mA with the below command

                #i2cset -y 1 0x09 0x14 0x0200 w

    Case 2: We remove the Adapter input Host Uc will be powered from the battery we can see that the (0x14) charge current register resets to 0000

    a) Is there any modification in the circuit that we can do to keep 0x14 set we can't always send this command through the host controller as it enters into sleep mode, during the event of charger adapter reconnected

    b) Can you please suggest any charger IC with 3Cell capability from a similar family where the charge register holds the value even when powered off?

  • 0 in reply to Atharv Rangnekar
    TI__Mastermind 23655 points

    Hi Atharv,

    I don't think there are ways (including circuit modification) to keep the register setting as the value will reset once adapter is removed.

    I am not sure if we have such charger but I can check with the team, meanwhile you can also search them on ti.com and check the charge current register behavior during POR/adapter removal in the datasheet. Will your adapter input always have higher voltage than the battery and system (in other words, are you looking for a buck, boost, or buck-boost)? What is the host interface you are using, I2C or SMBus?

    Regards.

  • 0 in reply to Tommy Lin
    Prodigy 41 points

    Hi Tommy 

    1) Did you get an alternate part in which the charge resistor will hold its value? 

    2) Can we supply battery voltage directly to VBUS with diode so that VBUS will always remain charge

    Thanks 
    Atharv 

  • 0 in reply to Atharv Rangnekar
    TI__Mastermind 23655 points

    Hi Atharv,

    We do not have a host controlled charger that hold ChargeCurrent register after adapter removal.

    Theoretically this setup can work but we never done this type of setup before. I would highly recommend ordering an EVM and test the modification on the EVM before proceeding the design.

    Regards.