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BQ25606: Charge Safety Timer Expiration

Sam Taylor-Jones
Prodigy 20 points
Part Number: BQ25606

Tool/software:

Hi All, 

We have implemented the BQ25606 into our product, and we are having some issues with what we expect is the charge safety timer expiring.

After exactly 10 hours, the STAT light starts blinking. We have measured the battery current in this state at around 3mA, which should be well below the termination current. 

I have attached a snippet of the relevant schematic, any insight that you may have would be much appreciated. 

All persistant loads are fed via V_SYS. The design includes some solenoids that operate directly from the battery, but these run for approx 20mS perhaps once in a charge cycle, so I doubt these are causing the described issues.

Thanks,

Sam

  • 0
    TI__Guru** 102965 points

    Hello Sam,

    We will look into this and get back to you by the end of the day.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Mastermind 33425 points

    Hello,

    My schematic review is as follows:

    1. 677 mA ICHG programmed.

    2. 4.208 V charge voltage regulation programmed.

    3. REGN needs a 4.7 uF 10V capacitor on it. This is essential.

    4. 1.02 A ILIM programmed.

    As for the STAT pin blinking after 10 hours, if the charge safety timer has expired at 10 hours charge will be suspended and the STAT pin will blink at 1 Hz.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 20 points

    Hi Mike, 

    I agree with your evaluation. What I dont understand is why the charge safety timer is expiring?

    As mentioned, the termination current drops to well below the threshold within the 10 hour timer. 

    Could the lack of capacitance on the REGN pin cause this?

    Thanks,

    Sam

  • 0 in reply to Sam Taylor-Jones
    TI__Mastermind 33425 points

    Hi Sam,

    As stated in Section 9.3.5.6, "During input voltage, current, JEITA cool or thermal regulation, the safety timer counts at half clock rate." Please check the mode while trying to terminate.

    I do not believe so, however we cannot support the operation of the device if the required components are not used in the design.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 20 points

    Hi Mike,

    Of course - I will fit the required capacitor and report back. 

    Thanks,

    Sam

  • 0 in reply to Michael Emanuel35
    Prodigy 20 points

    Hi Mike - changing the cap to the required 10uF does not solve our issue unfortunately...

    Thanks,

    Sam

  • 0 in reply to Sam Taylor-Jones
    TI__Mastermind 33425 points

    Hi Sam,

    Unfortunately the capacitor is required independently from this problem. I do not want you to get to production to find out you are missing a capacitor. Please include this capacitor in future revisions.

    The charge safety timer expires after 10 hours. You cannot shorten the safety timer. Can you please send a waveform of the VBUS, SW, VBAT, and battery current when you are observing this phenomenon (all on the same plot)? Please zoom in so I can see 100 ms per division. Also can you measure the input current at this time? The device will not terminate if in IINDPM or VINDPM or thermal regulation.

    Regards,

    Mike Emanuel