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BQ77PL900: I2C Communication Question

Christian John Barlis
Intellectual 885 points
Part Number: BQ77PL900

Team,

Posting this on behalf of our customer:

I'm looking to get some help technical help with a specific chip and get some clarity over a specific function I am wanting to do. I have a BMS chip with the product # BQ77PL900 and I have a question for the I2C communication. I am wanting to write directly to the STATE_CONTROL register to turn the chip output on/off depending on the message I am writing to the SDA and SCL pins. My concern is being able to turn it back on once I issue the shutdown command. I read in the documentation that it also requires a voltage greater than Vstartup applied to the PACK pin and was wondering if writing to the register directly to change modes back to normal will turn it back on?

Is there a specific message I can send via I2C from an external host to turn the chip output On/Off? 

Thanks for your help.

Regards,

Chris

  • 0
    TI__Guru 54715 points

    Hi Chris,

    If you write SHDN = 1 in the STATE_CONTROL register, the part will shut down when the PACK pin falls sufficiently.  If the PACK pin remains above the VI(STARTUP) voltage the SHDN bit can be cleared to continue operation.  The voltage is close to 0 as mentioned in the Power Modes section page 38 of the BQ77PL900 data sheet, but is not a characterized parameter.  If the PACK pin falls to 0V, the regulators turn off and the PACK pin must rise above VI(STARTUP) to turn on.   If the part is off the logic is off and can not accept a command to wake up.