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BQ76972: Bothoff behavior

Thomas Kofoed-Hansen
Prodigy 145 points
Part Number: BQ76972


Tool/software:

There is a sentence in chapter 7.8.7 of the datasheet that I must admit I don't understand. 

Note: when the selected pin is deasserted, the respective FET will only be enabled if there are no other items blocking them being reenabled, such as if the host also sent a command to disable the FETs using the serial communications interface after setting the selected pin.

If the FETs are enabled via I2C commands and the BOTHOFF pin is asserted the FETs will be released/closed, but what happens when the BOTHOFF signal is then deasserted. Will the FETs stay off until set via I2C or will they be activated again?

  • +1
    TI__Mastermind 19115 points

    Hello Thomas,

    If the command was sent to enable the FETs, but the BOTHOFF pin was asserted, the FETs will remain closed. However, if the BOTHOFF pin was then deasserted afterwards, if nothing else is disabling the FETs (e.g. a fault), the FETs should turn ON. The paragraph before Table 5-8. FET Control Subcommands in the technical reference manual may also help explain this. 

    Best Regards,
    Alexis