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BQ24090: charging TS PIN

Part Number: BQ24090

 It is found that when some products are charged, the charging value of the first 10 seconds is only half of the preset current value, and about 10 seconds later, the charging is normal. An oscilloscope was used to capture the voltage value of NTC when anomalies occurred, and it was found that the voltage value was abnormal.

1. As for the TS PIN Angle, the lithium battery now uses a NTC of 10K Ohms and B value of 3435, and the measured NTC value is 8.2K ohms. Within the resistance value range required by the specification, why is there abnormal NTC voltage? NTC appears this abnormal voltage, will let the charging IC misjudge into charging at that temperature? What is the logic of TS Pin?

 showing the waveform on the /CHG pin as below

 IN and OUT voltage also during this time as below

  • Hello

    The Vout waveform capture looks like a Batter Detection issue.  The high / low time of 25ms matches and Vout voltage (about 3.9V) is the area when this problem can be seen.

    Does the problem only occur at start up?

    If resistance between charger (BQ2409X) and battery is reduced does this change the behavior?

  • Does the problem only occur at start up?--------

    Yes, the problem all happened in the first charge, different prototype, charging abnormal to restore normal charge, it may take 10S, 5S, 40S or 30S, each time is uncertain  

    If resistance between charger (BQ2409X) and battery is reduced does this change the behavior?------

    At present, the resistance value between lithium battery and charging IC is about 600m ω at 3.9V. Does this resistance value meet the design requirements?  

    any advise?thanks in advance

  • Hello 

    This sounds like Battery Detection is tripping.  A couple of things to try, decreasing charger to battery resistance, changing charge current higher or lower. 

    As you noted the problem will clear on its own. 

  • Try to remove the PTC of the lithium battery and reduce the resistance of the charging circuit, but the problem did not improve.  

    Try to reduce the charging current, set the charging current to 250mA, and the charging can reach 250mA when powered on;  Raise the charging current to 450mA, and charge only 220mA, (half set value)  

    The charging current of the original prototype is set at 340mA, while the charging is only 170mA (half of the set value).  


    Based on the above tests, is this problem caused by the set charging current too large?  What is the normal setting range?   thanks in advance

  • Hi Raymond,

    Could you check the issue with different size batteries? May give us some clue what is going on.

    A few more requests

    1. Could you check TS and ISET pin during this time? Also good to check IOUT with a current probe.
    2. Can you attach the schematic for review?
    3. What is the size of the battery being used?