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LM3658: LM3658 the voltage of the TS pin fluctuates due to load changes

Star Xu
Genius 9645 points
Part Number: LM3658
Other Parts Discussed in Thread: BQ25170

Hi 

The customer design with LM3658, when the temperature reaches a certain value, the voltage of TS exceeds the threshold range, and the LM3658 turns off the charging process. At this time, due to the heavy load turning into no load, the voltage of the TS rises by about 40mv, and falls into the threshold range again.

The LM3658 turns on the charging process. In the process, the TS voltage is pulled down again, and then charging is turned off... This repeats, causing the charging IC to repeatedly turn on and off charging within a certain temperature range. Is there any way to improve the TS voltage fluctuation?

The schematic as below:

Please help check it.

Thanks

Star

  • 0
    TI__Genius 16405 points

    Hi Star,

    This is a legacy device and so unfortunately we don't have too much information available about this part, we typically recommending looking at newer components. The BQ25170 family offers similar simple implementations, though the power mux feature may be needed from a separate IC.

    Is the battery heating up significantly during charging? The current used to bias the NTC should be constant regardless of charging.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    TI__Genius 9645 points

    HI Juan

    Thanks for your reply.

    the battery is not heating up significantly.

    They used a potentiometer to simulate NTC, and the phenomenon continued when the resistance value was between 4.8kΩ and 5.2kΩ.

    Waiting for your reply.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Genius 16405 points

    Hi Star,

    As mentioned before, unfortunately we don't have too much information available about this part. I would check if the spikes in voltage correspond to any changes in input or output voltage as well as changes in current other than charge current to try to identify the cause. 

    It appears that it only occurs while the charger approaches the low-temperature voltage threshold, I'm unsure the level of hysteresis that was put in place for this device.

    Best Regards,

    Juan Ospina