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BQ76930: Tying the Alert Directly to Ground

Bill Meyer
Prodigy 20 points
Part Number: BQ76930
Other Parts Discussed in Thread: BQ78350

Hello TI, we have a design based on the 76930 battery monitor IC and the bq78350 companion IC. We are struggling with an ESD issue and have traced to the Alert pin. In the specification, the Alert pin has a 500K-1M Ohm pull down. We still have an occasional failure where the Alert disturbance is shutting off the CHG and DISCHG FETs. Can the Alert be directly pulled to ground and manage any flags through the serial port? If I can't tie directly to ground, how low of resistance can I go?

  • 0
    TI__Mastermind 42060 points

    Hello Bill,

    Pulling to ground or lowering the resistance would not solve this issue.

    You could add a capacitor (~470-pF) as shown as the BQ76930EVM User Guide in the ALERT pin, this may help prevent the false trigger. Make sure to place the external resistor/capacitor with short traces close to the IC.

    Let us know if this solved your issue.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 20 points

    Hello Luis:

    I was told by the testing team, removal of the capacitor improved the immunity. That's what lead to the question to tying directly to ground or through a low resistance. If we tie to ground, will this cause the IC to malfunction?  I want to insure it never exceeds the 1V threshold. 

  • 0 in reply to Bill Meyer
    TI__Mastermind 42060 points

    Hello Bill,

    I consulted with a team member, you could try and lower the resistance or short it, it may help if you are just trying to pass ESD testing. We've however seen that others have attempted this, and it did not find success in eliminating the false alert. This would also burn more current since the ALERT pin drives high any time a new set of measurements is available. 

    We usually recommend a 500-kΩ resistor in parallel with a 470-pF capacitor to prevent a false ALERT override protection from triggering.

    Best Regards,

    Luis Hernandez Salomon