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BQ2000: Battery removal and insertion detection

Takashi Onawa
Genius 13200 points
Part Number: BQ2000

Hi Team,

According to the datasheet, BQ2000 has Built-in Battery Removal and Insertion detect function but there is no explanation on the function in the datasheet.

Could you tell me what is the trigger of the detection?

In my customer's system, BQ2000 is at  "Trickle Maintenance Charge" when getting out the battery at charging.
They didn't expected this result because they thought it was back to start state when replacing a battery.
So they want to clarify how BQ2000 detects battery removal and insertion.

Regards,

Takashi Onawa

  • 0
    TI__Mastermind 24075 points

    Hi Takashi,

       Refer to figure 12. and figure 14. of the datasheet which show operation of removal and insertion of battery. Once battery conditioning (trickle charge) has raised the voltage on the BAT pin above VLBAT, the IC enters fast charge, if the battery temperature is within the VLTF to VHTF range. The BQ2000 will stay in the battery conditioning state indefinitely and will not progress to fast charge until the voltage on the BAT pin is above VLBAT and the temperature is within the VLTF and VHTF range.

    RC pin shows same status when battery is absent, and when battery is in conditioning state.

  • 0 in reply to Kedar Manishankar
    TI__Genius 13200 points

    Hi Kedar-san,

    Thanks for your prompt response on this.

    The point what my customer wants to know is event triggers of ”Battery Replacement”. That is not indicated in the datasheet.
    I wish BQ2000 would work as you have described above, but that is not the case with their system.

    How do they  make the transition from the "Trickle Maintenance Charge" state to the "First charge" state after the battery is removed and installed in "Trickle Maintenance Charge" state?

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 24075 points

    Hi Takashi-san,

       Form the state machine, the BAT voltage should be getting checked constantly. When the battery is removed, the output caps would be getting charged and discharged, which is why Figure 12. and Figure 14. have sawtooth waveform on BAT pin.

  • 0 in reply to Kedar Manishankar
    TI__Genius 13200 points

    Hi Kedar-san,

    I'm asking "trigger condition" to get BQ2000 know the battery removal event. 

    Could you tell me the specific threshold and logic condition of the event?

    BQ2000 can not recover to fast charging after the battery replacement because it could not reach to ”Charge Qualification State" due to any reason. So they want to understand the specific condition to have BQ2000 reset.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 24075 points

    Hi Takashi-san,

        When the battery is removed, the output capacitors would be charged up to MCV. Battery voltage should be monitored continuously and when VBAT < VMCV it will move on to the battery temperature monitoring and the rest of the charge process. Once VBAT falls and a new charge cycle is restarted, you will see the MOD pin pulse as charge is enabled and to switch, but as there is still only the output caps, they will be charged quickly. This is what you see occurring in the Figure 14. of the datasheet.

  • 0 in reply to Kedar Manishankar
    TI__Genius 13200 points

    Hi Kedar-san,

    Thank you for the supplementary explanation.

    I understood that one of important trigger is Vbat > VMCV condition after battery removal. So I have 2 quick questions.

    1.  I understand that if Vbat does not reach VMCV for some reason, the device cannot initialize the State machine, am I correct?
    As far as I see their capture after battery removal, Vbat peak voltage looks around 1.95V. So this might be a root cause of their issue.

    2. Is there anything they can do to increase the maximum Vbat peak voltage after battery removal? For example, changing the pulse width.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Mastermind 24075 points

    Hi Takashi-san,

       Only when the battery is not present will the output capacitors be charged quickly to VMCV. After charge initialization VBAT<VMCV is condition to start next phase of charging. Since the output caps charge quickly, they also discharge quickly, which would start the next charge cycle, where MOD will be turned on, as we immediately satisfy the VBAT<VMCV condition to start the state machine logic.

    We cannot change pulse width.