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BQ34110: Using alert pins to drive power supply enable lines

Christopher H
Prodigy 50 points
Part Number: BQ34110
Other Parts Discussed in Thread: TPS63070,

Hello,

I would like to use the BQ34110 to drive an enable line for a downstream power supply, such as the TPS63070. The enable line should deassert when the battery is below a voltage or power threshold. Driving ALERT1 with either BATLOW or SOCLOW states appear like good choices and I have observed ALERT1 making the proper transition when the battery is discharged below the BATLOW/SOCLOW set threshold. I do not, however, see the return transition when the battery is charged above the BATLOW/SOCLOW clear threshold.

The technical reference manual states, "The Alert1_0..6 Config and Alert2_0..6 Config signals are cleared upon a read of ALERT1STATUS() or ALERT2STATUS(), respectively." Is this the only technique for clearing the state of the alert line? I would like the BQ34110 to control the alert line completely by itself, toggling the enable on and off based on set and clear thresholds, rather than a downstream host processor which could be powered down and unable to query ALERT1STATUS(). Please advise.

Happy New Year,

Christopher

  • 0
    TI__Mastermind 25955 points
    Hi Christopher,

    The alert pins are set up to be cleared by the microcontroller. This allows multiple alerts to share ALERT1 or ALERT2. When the microcontroller is interrupted by ALERT1 or ALERT2, the microcontroller may digitially query the gauge by reading ALERT1STATUS() or ALERT2STATUS(), respectively, to determine what triggered the interrupt, and to clear the alert.

    However, to treat the pin as a charger enable, please use Direct Charge Pin Control. In this mode, while Voltage() is below the FC Clear Voltage Threshold, The pin will be asserted and subsequently deasserted when the FC Flag is set. ALERT1, ALERT2, VEN, or LEN pins may be used for this function. For more information, please refer to 2.9.2 Charge Control of the TRM.

    DCHGPOL will need to be asserted and DCP2-DCP0 set to determine which of the above pins should be utilized for this function.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Prodigy 50 points
    Hi Bryan,

    Thank you for the reply. To be clear, I would like for the BQ34110 to self-control a downstream regulator (to which the microcontroller is attached) rather than an upstream charger. It seems, however, that this might not be necessary. I was observing a significant load in the system which I thought was caused by the downstream regulator, but seems to have actually been the result of a damaged BQ34110. Replacing the chip seems to have solved the high load problem.

    Thanks,
    Christopher