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BQ24617: Charge termination when TTC pin is low

Luke Ereaut
Prodigy 30 points
Part Number: BQ24617

Our device uses the BQ24617 charger with the TTC pin tied to ground through a 10kΩ resistor. It is my assumption that in this configuration, charge should never terminate. However I'm noticing a relatively rare situation where some of our devices stop charging, and the STAT1 and STAT2 pins indicate charging is complete.

With TTC low, under what conditions will STAT1 and STAT2 indicate charging is complete? Or is this not supposed to happen?

Thanks.

  • 0
    TI__Mastermind 29992 points

    Hi Luke, 

    Thank you for reaching out!

    The TTC pin may be taken LOW to disable termination and to disable the safety timer. If TTC is pulled to VREF, the BQ24617 continues to allow termination, but disables the fast charge safety timer. Please see STAT pin definitions below: 

    Please let me know if you have additional questions. 

    Best Regards, 

    Aya Khedr 

  • 0 in reply to Aya Khedr
    Prodigy 30 points

    Hi Aya,

    I understand this, however it seems that despite having our TTC pin LOW, somewhat rarely we're seeing charge termination still take place (STAT pin state is "Charge Complete").

    I need to know if this is unexpected behaviour, or there is some condition in which this state can arise.

  • 0 in reply to Luke Ereaut
    TI__Mastermind 29992 points

    Hi Luke, 

    Yes, this behavior is not what we expect.

    Would it be possible to capture a waveform (charge current and STAT signals) when this behavior occurs? 

    Best Regards, 

    Aya Khedr 

  • 0 in reply to Aya Khedr
    Prodigy 30 points

    Hi Aya,

    Unfortunately I cannot capture waveform data at the moment as I don't have physical access to the few chips behaving this way.

    Ultimately I just wanted to confirm my assumption that this is in fact unexpected behaviour, which you've done. I have added code for detecting and handling this issue so it's not causing ongoing problems.

    If in the future I'm able to get some waveform data demonstrating this behaviour, I can make a new post and maybe we can troubleshoot why it's behaving this way.

    Thanks.