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BQ24179: 12V battery charger

Muhammad Awais
Intellectual 720 points
Part Number: BQ24179
Other Parts Discussed in Thread: BQ25792, BQ25798, TPS25751, TPS25730, BQ76922

Tool/software:

Hi, 

We have 12V battery that needs to be charged via USB-C PD. Our aim is to use simple and cheaper battery charging chip that also works with PD controller TPS25730SRSMR. I came up with many options like BQ24179, BQ25792 and other too but please suggested the best suitable option. 

I have another question that for these chargers is it must to connect USB data lines to the Charging IC? I am asking this as our MCU (ESP-32) in our case needs to boot/program via USB so if the charging IC needs the USB-C data pins to be connected then we will not be able to use the USB datelines for MCU debug/program. 

Thanks and regards,

Muhammad Awais

  • 0
    TI__Guru**** 166076 points

    Hi Muhammad,

    We have a reference design with TPS25751 + BQ25798 at https://www.ti.com/tool/USB-PD-CHG-EVM-01.  The TPS25751 firmware controls the BQ25798.  BQ25798 is the descendant of BQ24179 so it has the same I2C registers.  In theory (meaning not tested), the same TPS25751 should control the BQ24179. 

    The charger IC has D+/D- to detect output current capability of only USB BC1.2 legacy chargers.  The charger IC cannot communicate directly with a USB-C port.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 720 points

    Hi Jeff, 

    Thanks for your answer. Can you please confirm if we can use TPS25730 with this BQ25798 ? Also, what is the benefit of using TPS25751 + BQ25798?

    Sorry, I don't get this. Can you please explain and clarify that we shouldn't be connecting the D+/D- to the USB-C connector?

    "The charger IC has D+/D- to detect output current capability of only USB BC1.2 legacy chargers.  The charger IC cannot communicate directly with a USB-C port."

    Kind regards,

    Muhammad Awais

  • 0 in reply to Muhammad Awais
    TI__Guru**** 166076 points

    Hi Muhammad,

    If you want to write your own firmware from scratch, then you can use TPS25730.  TPS25751 already has firmware that controls the BQ2579x/719.

    The charger only uses the D+/D- to set its input current limit to match the output current capability of a USB BC1.2 source.  USB-C sources do not use D+/D- lines to do that.  Instead, they use CC1/2 to negotiate a power contract.  Then either TPS257xx firmware or MCU software sets the charger's input current limit.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 720 points

    Hi Jeff, 

    Thanks, I will look into TPS25751. 

    Regarding the D+/D- so I will use it to debug the MCU instead and will not connect the USB data lines to the Charger IC. 

    Kind regards,

    Muhammad Awais

  • 0 in reply to Muhammad Awais
    Intellectual 720 points

    Jeff, 

    We still have to use the Application customization tool to set the parameters for both the PD controller and battery charger in case of TPS25751? In our case we are going to use the custom board so I am assuming we can't use the application customization tool. Please confirm. 

    That means without the loading the firmware the PD and charger chip will not work or they will at their default state based on the hardware settings?

    Kind regards,

    Muhammad Awais

  • 0 in reply to Muhammad Awais
    TI__Guru**** 166076 points

    HI Muhammad,

    I recommend starting with the tool and then modifying the firmware to fit your needs.  

    The charger chip functions in default mode as long as input power is supplied.  The TPS25751 only reconfigures some of the I2C registers from their default configurations, most importantly the IINDPM setting so that it matches the output current from the USB-C contract.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 720 points

    Hi Jeff,

    Sure, will do. 

    Lastly, what is the use of BQ25792 and BQ25798 has the USB and as you said in our case we will use the CC1/CC2 to do the handshaking between USB-C header and PD controller. 

    What is the purpose of USB interface on these battery charging ICs? Is it for the case if we don't have any PD chip in between like if we will directly connect BQ25798 input to the USB-C and this charging IC will handle the handshaking through USB DP/DN? If so then any limitation in using complete 5-20V 100W input? Here is what the datasheet states so please help me to clarify my points. Thanks

    I have asked to check if we may exclude the PD chip as in our application price is a point take care of.

    Kind regards,

    Muhammad Awais

  • 0 in reply to Muhammad Awais
    TI__Guru**** 166076 points

    Hi Muhammad,

    The charger's D+/D- lines are for legacy USB BC1.2 ports and some high voltage DCP adapters (e.g. some QC2.0 adapters).  USB-C does not use D+/D- for determining output power requirements. USB-C uses the CCx lines. If you want the USB-C port to provide higher than 5V and 500mA, you will need a PD controller chip.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 720 points

    Thanks Jeff for your help and clarification. 

    Kind regards,

    Muhammad Awais

  • +1 in reply to Muhammad Awais
    Intellectual 720 points

    Hi Jeff, 

    We are finally using BQ25798 for our 3s-4s battery charging. Can you please suggest any cell balancing IC as the battery has no on board balancing. Please suggest options with smaller footprint and low external parts count. I am currently looking into BQ76922 but please let me know if there is any better option with least external parts and lower cost as my sole purpose is to balance the cells. Thanks

    A second question that mostly we need a dedicated microcontroller that will monitor the cell balancing but in our case as we will have the cell balancing and Battery charging IC on our board and we will only have a single ESP32 that will be running on power form the battery and will be used for our actual system so can I use the same processor I2C to the cell balancing IC. I need to  know if we need to setup the cell balancing IC via I2C before it will start working if all cells are OK? 

    Thanks and regards,

    Muhammad Awais