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BQ40Z50-R1: 400kHz SMBus XL mode

Chang Zhong
Prodigy 60 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ40Z50, BQEVSW, BQSTUDIO, EV2400

I am developing the 400kHz SMBus feature for our product recently, but when I set XL to 1 and RESET the fuel gauge, I can only read some registers correctly (e.g. ManufacturerAccess 0x00 ). I've tried to search related information in this forum and found the following information.

The SMBus XL mode can only be used to load the srec file into flash memory while in ROM mode.   Link: e2e.ti.com/.../413209

Is it true? I didn't find any tips mentioning this kind of restriction in th datasheet. Is there anything else I missed for SMBus XL 400kHz mode?

Thank you!

  • 0
    TI__Genius 14985 points
    It is true. The bq40z50 was released before the 400kHz SMBus spec was released, so SMBusXL is our way to support high-speed flash programming by packmakers, but it only works in ROM mode and not when running FW.
  • 0 in reply to dMax
    Prodigy 60 points
    Thank you, dMax! I have other 3 questions.
    1) How can BQ40Z50 enter the ROM mode? And how can it exit the ROM mode?
    2) I set XL to 1 and RESET the fuel gauge. Now I can't use EV2300 to change XL back to 0 with bqEVSW. What should I do to switch my BQ40Z50 back to normal mode.
    3) Could you please recommend a battery fuel gauge which can support 400kHz fast mode when running FW?
  • 0 in reply to Chang Zhong
    TI__Expert 6575 points

    Hi Chang,

    1. To enter ROM mode send a Word write to 0x00 with word 0x0F00 and to exit ROM mode send the command 0x08:

    2. To switch the mode back, you will need to make sure that you are using the "TEST" version of bqStudio (v1.3.86.3) that you can download from the http://www.ti.com/tool/Bqstudio . Under preferences->Charger, you can then select the High Speed EV2400 I2C clock that should allow you to talk at the higher speed and change the XL bit back to 0:

    3. At the moment we don't have any gauge that is fully compliant to the 400kHz SMBus specification.

    Regards,

    Swami