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BQ25798: Single Die PMIC Solution for Multiple Power rails with Li-Ion Battery Charging

Dhruvit Bhimani
Intellectual 280 points
Part Number: BQ25798
Other Parts Discussed in Thread: BQ25505, TPS2121

Tool/software:

Hello TI Team,

I am looking for a single-chip power management solution that can handle multiple input power sources, charge a Li-Ion backup battery, and provide multiple output voltages while supporting communication via I2C/SPI for monitoring and control. Below are the detailed requirements:

Input Power Sources:

  1. External Input Source: 5V to 20V

  2. USB Input Source: 5V

  3. Solar Panel Output: 2V, 0.3W (Adafruit Product Link)

    • The solar panel will be always connected, but at night it becomes unusable.

    • In such cases, either the USB input, external input, or battery backup will be used.

Battery Backup:

  • 3.7V Li-Ion Cell, 7800mAh

  • The battery must be charged from any available input source (External/USB/Solar).

  • Built-in fuel gauging is required to monitor battery status.

Output Power Requirements:

  • 12V @ 350mA

  • 5V @ 2A

  • 3.3V @ 2A

Control & Monitoring:

  • The power system should be monitorable and configurable via I2C or SPI communication.

Required Features:

Priority-based power selection (Auto-switching between inputs)
Efficient MPPT charging support for the solar panel (i.e: SPV1050TTR)
Battery charging management with safety features
Fuel gauging for battery monitoring
I2C/SPI communication for control & status monitoring

Can you please suggest a single-die PMIC (Power Management IC) from TI that can fulfill these requirements?

Thanks in advance!

  • 0
    TI__Guru**** 166696 points

    Hi Dhruvit,

    I am not aware of a single chip PMIC that provides all of these features.  The BQ25798 battery charger has MUX drivers to switch between 2 inputs.  It's SYS output is the higher of the MINSYS voltage or battery regulation voltage (i.e. not a regulated 3.3V or 5V).  So, you would need 2 boost converters and a buck converter for the outputs.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 280 points

    Hi Jeff,

    Thanks for your response.

    Currently, I am using six different power regulation circuits:

    • 5V Buck Converter

    • Battery Charger

    • MPPT Solar Energy Harvester

    • 12V Boost Converter

    • 5V Boost Converter

    • 3.3V Buck Converter

    My goal is to minimize the number of components and simplify the design as much as possible.

    The MPPT solar energy harvester may require a separate IC, but if there is a single PMIC that can integrate the other functions, it would be ideal. Do you know of any PMIC that would suit my requirements?

    Thanks in advance!

  • 0 in reply to Dhruvit Bhimani
    TI__Guru**** 166696 points

    Hi Dhruvit,

    The BQ25798 charger has MPPT function but it does not function below 3.6V panel input.  You can search TI's PMICs at https://www.ti.com/power-management/multi-channel-ics-pmic/products.html.  There are reference designs at https://www.ti.com/reference-designs/index.html likely include multi-output solutions using multi-tapped transformer.

    Your power levels don't add up.  The 0.3W panel cannot provide the power below:

    • 12V @ 350mA

    • 5V @ 2A

    • 3.3V @ 2A

    To get power from 2V solar panel, you could use BQ25505.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 280 points

    Hi Jeff,

    This time, I have used a different approach. I need a buck-boost converter that can provide the following outputs:

    • 5V buck output

    • 3.3V buck output

    • 12V boost output

    The input supply to the buck-boost converter will come from a PMIC, which manages battery charging, solar, external VIN, and USB power sources.

    The VSYS pin of the PMIC can go up to 18V, depending on the available power source.

    Do you know of any suitable buck-boost converter that meets these requirements?

    Thanks!

  • 0 in reply to Dhruvit Bhimani
    TI__Guru**** 166696 points

    Hi Dhruvit,

    TI does not have such a PMIC.  I do not support buck-boost converters, only chargers.  The BQ25798 with TPS2121 could charge your battery with 3 input MUX.  But again, the minimum input to the charger is 3.4V, which is below your solar panel's VOC.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 280 points

    Thanks for your help till now, let me create new thread for buck-boost converter.

    Regards,

    Dhruvit 

  • 0 in reply to Jeff F
    Intellectual 280 points

    Hi Jeff,

    I found an IC that fits all my buck configuration requirements.

    I’d like to confirm whether the BQ25798 can provide a non-interrupted 5V supply on the PMID or VSYS pin when no external supply is connected, but a 3.7V battery is connected to the PMIC.

    Looking forward to your clarification.

    Best regards,
    Dhruvit

  • 0 in reply to Dhruvit Bhimani
    TI__Guru**** 166696 points

    Hi Dhruvit,

    798 cannot provide regulated 5V on SYS and charge a battery.  798 can provide a regulated 5V on PMID if 

    1. VBUS =5V is applied for charging the battery since there is only a FET between VBUS and PMID.  Note that the current pulled from a load PMID is deducted from the 3A total available to charge the battery.

    2. if host I2C enables backup mode after VBUS is removed.

    Regards,

    Jeff