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BQ76920: implementing without bq78350-r1

Ran Aloni
Expert 2365 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ78350-R1, BQSTUDIO, BQ78350, TIDA-00449, BQ76930, BQ76940, BQ76200

Hi all,

I would like to use the BQ76920 chip without it's companion chip bq78350-r1.
few questions:

  1. how will I be able to change protection parameters? is there a UI for that? (since bqstudio will not work).
  2. how can I have the pre-charge option - since the pin is in the bq78350 part?

  3. I plan to use the 76200 ic to have high side latch, can I implement pre-charge from this IC instead?

many thanks,
Ran Aloni

  • 0
    TI__Guru 54715 points
    Hi Ran,
    TIDA-00449 is an example implementation of a bq769x0 family device without bq78350-R1 and may be useful.
    1. For evaluation see the "bq76940/bq76930/bq76920 Evaluation Software" in the bq76920 product folder Tools & software tab. In your product you will need to save your settings in the MCU and send to the bq76920.
    2. Your MCU can signal pre-charage much like the bq78350-R1
    3. The bq76200 is a high side FET driver. It has a driver for a P-channel pre-charge FET, that does take some bias current so depending on your usage you may want your own driver to optimize for low current.
  • 0 in reply to WM5295
    Expert 2365 points

    Hi Willy,

    I'm not planning on having an MCU on my board, the idea was to have a protection circuit with programmable parameters.

    so my option is to prepare a "configuration board" with an MCU on it to set the parameters, right?

    also I can connect it to the evm to an BQ78350-R1 (but then I have to make sure that the BQ76920 is with 0000 or 0001 sufix).

    about precharge:
    in previous design, I used the bq78350-r1 and the 76200, and precharge was always enabled. is this what you refer as "bias current" ?

    thanks, Ran

  • 0 in reply to Ran Aloni
    TI__Guru 54715 points
    Hi Ran,
    If the MCU is disconnected, the bq76920 will continue to run until some fault turns off the FETs. It then needs to MCU to perform any appropriate checks and recover from the fault. If the system is designed with the bq76920 the battery and the MCU in another part of the system it should work as designed. However do notice that the bq76920 does not provide temperature protection, it relies on the MCU to provide the temperature decisions and FET operation.
    The bq76200 uses some current to turn on the precharge driver. If the system recognizes the charger is present and turns on the appropriate FET, current consumption from the battery is minimized. If the battery sees its voltage drop and turns on the pre-charge circuit waiting for the charger to be attached, current consumption may be increased. A system which keeps precharge on waiting for charger attachment may want a minimum current in the precharge FET driver.
  • 0 in reply to WM5295
    Expert 2365 points
    Hi Willy,
    let me verify this :
    although the IC has a TS1 pin the IC won't react to a over/temperature event? only if read by another entity (BQ78350-R1 or MCU) over I2C and get the order to open CHG/DSG FET?
    thanks!
  • 0 in reply to Ran Aloni
    TI__Guru 54715 points
    Hi Ran,
    Correct. The TS1 pin allows temperature measurement if selected. The MCU must act on that measurement and open FETs when and if desired.