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BQ25710: In-device charging with regen-capable BLDC device

Vincent Politzer
Prodigy 60 points

Part Number: BQ25710
Other Parts Discussed in Thread: BQ40Z50, , TPS25730, BQ25730, BQ40Z50-R2, PMP41013, TPS25751, BQ25720

Hi Texas Instruments team,

I am working on a charging concept where we actually integrate USB PD charging into our device, so the user can leave the removable battery in the device and simply connect a USB-C charger. I would like to solicit your assistance/feedback. There are some specific requirements we need to keep in mind.
  • The device's battery is user removable.
  • The device has a BLDC motor.
  • The device battery should be rechargeable via a USB-C port w/ USB PD on the device.
  • The device would not be "fully-powered" by the USB charging port, it would primarily serve to charge an installed battery, or perhaps facilitate some system update or debugging over USB while powering the primary processors, but the motor shall not engage without a battery installed.
  • The device is capable of generating "regen" current during use, which results in current flow back into the battery.
    • The charger can under no circumstance disconnect the battery when there is regen current, as doing so can result in high system voltage peaks, which may destroy other components in the circuit. Only the BMS should be responsible for cutting power for protection purposes. (BATTDRV function may conflict)
  • Our POR battery will use the BQ40Z50 BMS IC, and SMBUS is available to our device.
  • We may not have additional I/O to communicate with the charger, except for the existing SMBUS connection to the BMS.
  • The charger must be configurable to terminate charge at <100% SoC (Such as 90% charge limit, for lithium cycle health, etc.)
I was looking at the BQ25710 charge controller and the TPS25730 USB controller, but am interested in your input. An architecture where the charging circuit can just sit in parallel to our system load on the battery, with a diode to prevent regen current from flowing back into the charging circuit, might make sense to satisfy the aforementioned requirements. Also, can our host processor communictate/configure the charge controller via SMBUS, while simultaneously communicating to the BMS, or does the BMS communicate directly to the charge controller?

I look forward to your suggestions!

Regards,
Vincent Politzer
  • +1
    TI__Mastermind 35765 points

    Hi, Vincent,

    BQ25710 will work. We have some reference design online. BQ25730 is ever better. 

    PMP41013 — Integrated USB Type-C® and USB PD bidirectional charging reference design for 1- to 5-cell battery

    If you have a host processor, it is easier to let the host controller to communicate to the charge controller. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 60 points

    Hi Tiger,

    Thank you! I see that these other parts use I2C instead of SMBUS. Since the BQ40Z50-R2 we are currently specifying in our battery uses SMBUS, does it make sense to have both I2C for the host-to-charger communications, and SMBUS for host-to-battery, or do you recommend a different gauge chip so we can share the I2C bus?

    Thank you for the link to PMP41013, that is really helpful for our development.

    I saw that the TPS25751 has moisture detection – this is actually desirable in our application. Am I correct in understanding the communication architecture, that we should let the host controlller communicate to the TPS25751 USB controller, and the USB controller would then communicate with the charge controller? Also, since we have a host, the EEPROM is optional, since the host can load the configuration at boot?

    Best,
    Vincent

  • +1 in reply to Vincent Politzer
    TI__Mastermind 35765 points

    Hi, Vincent,

    The battery gauge devices are outside of my focus area. Alternatively, you can use BQ25720 which is a SMBus battery charger. It is common to have MCU to communicate to PD, battery charger and other devices. 

    Regards,

    Tiger