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BQ24195L: Schematic Review Request: IR Controller with BMS

Peter Grinalds
Prodigy 160 points
Part Number: BQ24195L

Tool/software:

Hello there,

We are designing an IR transmitter for a customer and plan to use the bq24195L as the BMS for the system. The controller will have a single 3.7V LiPo battery and be charged through USB. The current load will not be large for the controller, but we want to have a reliable design in case we increase load in the future. Would you kindly review the schematic and provide any input? We do have several questions in particular:

  • USB input: we are populating a USB connector that will be the primary power source during charging. Does the USB interface on the bq24195L chipset allow for direct programming and monitoring during debugging or would that only happen through I2C from the host IC? We will be using an RP2040 for the host, can we simply connect the BQ data lines to that bus for triggering? What is the most reliable approach here?
  • PMID: We are not certain if using boost would be useful in the product. Is this used during times of peak current? Or it for achieving voltages larger than 5V?
  • For our own understanding can you confirm that the following is true? The battery will be connected to the BQ and the BQ will provide power to the rest of the board (through SYS pins), arbitrating when to use the battery and when to provide power from the USB port. Is that correct?

Thank you so much for your counsel and consideration,

Peter

battery_controller.pdf

  • 0
    TI__Genius 17585 points

    Hi Peter,

    Based on the provided schematic, all the component values and circuit designs look appropriate. For the ILIM resistor, it appears that an absolute max ILIM of 1.6 A is programmed so this should be taken into consideration for . Everything else looks like a typical application. Typically we recommend 10kOhms pull ups for the I2C lines but this can vary depending on other devices on your I2C bus, I think 1kOhms should be ok.

    Peter Grinalds said:
    USB input: we are populating a USB connector that will be the primary power source during charging. Does the USB interface on the bq24195L chipset allow for direct programming and monitoring during debugging or would that only happen through I2C from the host IC? We will be using an RP2040 for the host, can we simply connect the BQ data lines to that bus for triggering? What is the most reliable approach here?

    The USB interface on the BQ24195L is used for D+/D0 detection per USB specification BC1.2. This helps determine the current limit of the connected USB source. This functionality can be read in section 8.3.1.3.4 of the Datasheet. These pins do not have USB communication functionality. Communication with the BQ24195L is meant to take place primarily through the I2C lines with a host controller. It appears the RP2040 does have 2 I2C controllers embedded. I would recommend using these resources to communicate with the BQ24195L, with the appropriate pull-up circuit connected to the device I2C lines.

    Peter Grinalds said:
    PMID: We are not certain if using boost would be useful in the product. Is this used during times of peak current? Or it for achieving voltages larger than 5V?

    The Boost mode or "OTG" mode is used in applications where the USB port is used to power other devices via USB. For example, a battery bank that uses USB to be charged but also uses USB to output 5V. Since it is for USB-OTG the boost output is 5.1V.

    Peter Grinalds said:
    For our own understanding can you confirm that the following is true? The battery will be connected to the BQ and the BQ will provide power to the rest of the board (through SYS pins), arbitrating when to use the battery and when to provide power from the USB port. Is that correct?

    This is a correct understanding of the power-path feature. The BQ will prioritize drawing power from the USB for charging and for SYS powering. When the USB is current/power limited, or when it is not available, the BQ will draw on battery power to power the SYS load. The SYS load is typically the power for the rest of the board.

    Best Regards,

    Juan Ospina