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BQ25792: interfacing to BQ40Z50-R1

Hazar Mutgan
Prodigy 50 points
Part Number: BQ25792
Other Parts Discussed in Thread: BQ40Z50-R1, , BQ25798, BQ40Z50

Tool/software:

hi,

we are planning to use a battery pack that has BQ40Z50-R1 and we picked the BQ25792 as the charger. 

since the ntc is in the pack and connected to BQ40Z50-R1, can BQ40Z50-R1 and BQ25792 talk to each other and adjust the jeita tresholds?  what is the best way to do this?

thanks,

h

  • 0
    TI__Guru**** 157141 points

    Hi Hazar,

    No.  Host firmware is needed for communication between BQ40Z50 and BQ25792.  BQ25792 is not SMBUS compatible and uses I2C not SMBUS.  If the application allows for user removable battery, I suggest changing to BQ25798 with is pin2pin and register2resistor compatible.  Also, BQ2579x TS function must be either hardware disable with matching resistor divider from REGN to TS to GND or via I2C write to turn off TS function.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 50 points

    hi jeff,
    thank you for the reply,
    can you please elaborate why BQ25798 is recommended for user removable battery?

    regards,

    h

  • 0 in reply to Hazar Mutgan
    TI__Guru**** 157141 points

    Hi Hazar,

    If no battery is connected at BAT and charge is enabled, both 792 and 792 charge current turns on fast and results in BAT and usually SYS overvoltage if the minimum recommended capacitance for BAT is used.  When this occurs, 792 turns off the converter for 30ms, which causes SYS voltage to collapse.  798 does not turn off the converter. If you add about 200uF to BAT pin, the OVP does not occur.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 50 points

    hi jeff,

    thanks for the clarifications. coming back to original question, does ti have any sample code or recommended way to communication between BQ40Z50  and BQ25792 via host processor to handle ntc  and  jeita charging profiles?

    regards,
    hazar

  • 0 in reply to Hazar Mutgan
    TI__Guru**** 157141 points

    Hi Hazar,

    There is no sample code for communication between those 2 specific ICs.  The thermistor can only be connected to either the BQ40Z or BQ25792, not both.  If connected to BQ40Z, the host software must periodically read the thermistor voltage and make a determination whether charge should continue or change and then write any changes via I2C to the BQ25792.

    There may be generic code for the BQ40Z.  I will forward this post to the group that supports that device.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Mastermind 24795 points

    Hi Hazar,

    The document below contains information on how to communicate with our gauges. Please let us know if more information is needed:

    https://www.ti.com/lit/pdf/slua801 

    Regards,

    Anthony