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BQ24192I: Incomprehensible timer fault

Kuramochi Tadahiko
Guru 28715 points
Part Number: BQ24192I

Hi,

Incomprehensible timer fault(REG09[4:5]=11) occurs only when precharge set into 128 mA.

This fault doesn't occur when precharge set int 256 mA.

And current and timing is various when fault as follows:

・Case 1：　3h06m  86mA　
・Case 2：　0h36m  845mA
・Case 3：　3h14m  171mA
・Case 4：　3h11m  171mA
・Case 5：　3h01m  238mA 

Register setting and conditions are follows;

AC Adapter 12V
 　  The Charge Start  Voltage ：about 2.6V
　　Input Voltage Limit VINDPM: 4.68V
　　Input Current Limit IINLIM: 1.5A
　　Fast Charge Current Limit  1.344A
　　Precharge　Current Limit： 128ｍA/256mA 
　　Termination Current Limit：128mA
　　Watchdog: Disable
　　Fast Charge Timer Setting： 5h
　　Others：Default

What is the cause of this fault?

Please let me know if you need schamatics.

Best Regards,

Kuramochi

  • 0
    TI__Expert 8230 points

    Hello Kuramochi,

    REG09[4:5]=11 refers to a safety timer expiration fault. Currently, your safety timer setting is 5 hours.

    Couple questions:

    -Do you have a charge cycle log? How long is the charge cycle taking to complete (from your starting voltage to termination)?

    -What is the capacity of your battery?

  • 0 in reply to Fernando Lopez
    Guru 28715 points

    Fernando-san,

    Thank you for your support.

    I attach the charge cycle data.

    BQ24192I Charge cycle.xlsx

    And battery capacity is 2835mAh.

    Please let me know if you need more information.

    Best Regards,

    KUramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Expert 8230 points
    Hello Kuramochi-san,

    I don't see anything abnormal from the CCCV plots provided.

    Currently, is your host disabling the safety timer first by clearing REG05[3] before configuration of the timer and charge enabled? To ensure proper safety timer operating, it is recommended to disable/re-enabled the timer first by using REG05[3]. This is mentioned in section 9.3.3.6 of the bq24192i datasheet.

    I recommend verifying the latter is implemented and repeating a charge cycle by re-enabling the safety timer prior to charge starting.