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Original question:

BQ76942: Sleep Wake signal

BQ76942: Use alert pin to awake MCU when discharge current reaches a threshold

Brian Wang0
Expert 5310 points
Part Number: BQ76942

Hi team,

If we would like BQ76942 alert pin to set high when discharge current reaches 50mV so we could use the alert pin signal to awake the MCU.

How to do the configuration? Thanks!

  • 0
    TI__Guru* 81034 points

    Hi Brian,

    I'm not sure I understand: do you mean 50 mA for the discharge current?

    For this behavior, you can set the following settings:

    • REG0 Config = 0x01, REG12 Config = 0xD  (In this example, I set the REG1 to 3.3V )
    • ALERT Pin Config = 0x2A (Set the ALERT pin to drive 3.3V when asserted, 0V when off)
    • Default Alarm Mask = 0xF801  (Set the WAKE bit so that the ALERT pin goes high when the device exits Sleep mode)
    • Sleep Current = 0x32  (Set Sleep Current to 50 mA)
    • Power Config = 0x2980 (set WK_SPD bits to 0x00 according to recommendation in latest TRM to avoid accidental wakeup due to nosie)

    When the device exits Sleep mode, the ALERT pin will go high with these settings. Then, you need to write 0x0001 to the Alarm Status register (0x62) to clear the WAKE bit to reset the ALERT pin.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Expert 5310 points

    Hi Matt,

    Sorry I had just noticed the reply.

    The understanding is slightly different from what we meant.

    Customer are trying to use the alert pin to awake MCU even when AFE is awake. So we prefer to use 50mV OCD to pull up the alert pin rather than sleep event.

    Please also note customer do not what any protection actions when this 50mV OCD happens since it is only used to alert the MCU. Is it possible to do so?

    Regards,

    Brian

  • +1 in reply to Brian Wang0
    TI__Guru* 81034 points

    Hi Brian,

    You can set the DSG FET Protections A register to 0x80. This will configure the DSG FET to only disable in the case of a SCD and not for OCD. 

    Regards,

    Matt