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BQ25306: Regarding STAT output when battery is not conected

Daisuke Higa
Genius 3635 points
Part Number: BQ25306

Tool/software:

Hi support team all.

I have a question about the STAT output when the battery is not connected.
The conditions are as follows:
- A circuit with the "power path" added as shown in Figure 10-8 on page 25 of the datasheet.
- The battery is not connected.

My questions are as follows:
- Is the VBAT voltage VBAT_short = 2.2V (typ)?
- What kind of output is the STAT output?
I found other posts (below).

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/962083/bq25306-stat-pin-is-strange-when-battery-pack-is-not-attached?tisearch=e2e-sitesearch&keymatch=BQ25306%25252520STAT#


However, I was unable to find the "deglitch time" mentioned in the post in the BQ25306 datasheet.
If the STAT output is output at a constant pulse period, I would like to estimate that period, so please tell me the formula for calculating it.

Best regards,

Higa

  • +1
    TI__Mastermind 21685 points

    Hi Higa, 

    Please see my comments below. 

    Daisuke Higa said:
    - Is the VBAT voltage VBAT_short = 2.2V (typ)?

    With no battery connected, but the BQ25306 IC enabled via /EN pin the BAT pin voltage will be regulated to the battery regulation voltage set via the resistor divider at FB pin. As the previous post you linked mentions the charger IC will charge the BAT output cap as if it is a really small battery. 

    Daisuke Higa said:
    - What kind of output is the STAT output?

    In the condition of no battery the STAT pin will periodically transition between High and Low status to indicate the device is transitioning back and forth from charging state and charge complete state. The device transitions back and forth frequently due to the small cap quickly charging then discharging. 

    The exact pulse period will depend on the amount of output capacitance at BAT, but the waveform from the linked post is a good reference point. STAT is LOW to indicate device in charging state then HIGH to indicate charge is terminated. 

    The device has a termination deglitch time of 40msec, which means the charge current must be below the termination threshold for 40 msec to stop charge. I do not have a specification available to share regarding recharge deglitch time, but recharge deglitch just means the device will remain in the termination state for a min amount of time (in the msec time range). 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Genius 3635 points

    Hi Garrett-san

    Sorry for the delay.

    Thank you for answering.

    I understood well.

    Best regards,

    Higa