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Inquiry regarding TCOLD Fault on bq24250

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: BQ24250

Wenjia-san, 

Thank you for your continuous support towards the inquiry regarding bq24250 from our customer.

In addition to the inquiry regarding charge status on bq24250, I have some additional inquiries regarding TCOLD Fault on bq24250 from them.

Please refer to the items below, and feedback us with your comment.

On this inquiry, they are evaluating their own prototype with another battery which NTC Beta is 3435 degK.

This means that they changed the resistors value around TS pin from EVM as, R5=5.1kohm and R6=10kohm.

Also, this prototype could be connected to USB Interface Adaptor to control from GUI.

On this configuration, they found TCOLD Fault on GUI when battery plugged-in. This issue could be found occasionally, not depending on battery charged level.  

On this case, the LED is  turned on, but never turned off again (For more than 12 hours).

Also, we tried to do CE toggle from GUI and connecting CE pin to GND. However, this issue could not be resolved.

We assume that we need to add capacitor in parallel with R6 to absorb noise which is caused on plugging-in.

On this case, please let us clarify which capacitance would be suitable.

We thank you once again for your information.

Best regards,

  • 0
    TI__Expert 7730 points

    Hi Okui-san,

    When the temperature is between TS_Cool and TS_Cold, the charge current is be cut in half and the safety timer will be doubled, which should be the reason why the IC keeps charging for 12 hours.

    However, the IC is dynamically monitoring the TS pin voltage and will change the charging status accordingly. So, if the transient on TS caused the TS fault when the battery is plugged in, the TS fault should be recovered once the voltage is stabilized. If the TS fault stays, can you measure the voltage on TS pin and see if it is truely below the TS_Cool threshold?

    Thanks,

    Wenjia

  • 0 in reply to Wenjia Liu
    Genius 4015 points

    Wenjia-san, 

    Thank you for your prompt reply on this inquiry.

    Now we are awaiting for their feedback regarding voltage on TS pin and VLDO to check whether %VLDO is really between VCOOL and VCOLD thresholds.

    For our side, since we still could not observe customer's situation on EVM, then I tried to use R7 to see how GUI would show in case between TS_Cool and TS_Cold.

    This could be observed when setting R5=5.1kohm and R8=38.28kohm.

    I also found once strange point regarding the customer's case. 

    For our side, when between TS_Cool and TS_Cold, the LED could be turned off if Disable Charge is checked on GUI. However, our customer could not. (LED could never be turned off unless removing battery.)

    We would appreciate if you could feedback us with your suggestion to check on their board additionally. 

    We thank you once again for your information.

    Best regards, 

  • 0 in reply to Atsushi Okui
    TI__Expert 7730 points

    Hello Okui-san,

    Thanks for the additional information.What I observed on bench is the same as what you saw - both LEDs will turn off if I disabled charge in the GUI. Can customer share the schematic with us?

    Also, on customer's board, if the TS is in the regular operation range, can the LED be turned off if the charge is disabled through the GUI?

    Thanks,

    Wenjia