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BQ27441-G1: Sleep mode behaviour

Danilo A.
Mastermind 28840 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hi Team,

Can you please help us with our customer's inquiry below.

We are trying to configure BQ27441 to go to sleep mode for a certain sleep current value.

We are still testing this feature, and we configured the sleep mode to be 240 mA. Since the average current in our testing product is 80 mA, we expected the BQ27441 to go to sleep mode after this configuration, and this what really happened. 

However, by continuously reading the status register, we found that it toggles between the normal mode and the sleeping mode for each second. I do not know the reason behind this behavior. It should remain in the sleeping mode for at least 20 seconds but what I saw was that it kept going back to the normal mode. Could you please explain the possible reasons behind this behavior? did we miss something in the configuration?

Regards,

Danilo

  • 0
    TI__Guru 57697 points

    Hello Danilo,

    Please see TRM section 2.4.5 SLEEP Mode

    Alternatively, an early wake-up before the 20-second internal is possible if the instantaneous current detected by an internal hardware comparator is above an approximate threshold of ±30 mA.

  • 0 in reply to Shirish
    TI__Mastermind 28840 points

    Hi Shirish,

    Thank you for your response. Our customer has follow up inquiry below.

    I think it is clear now. It is waken-up because the current in our product is 80 mA which is higher than the threshold 30mA. However, what is the point of letting the user configure the sleep current up to 1000 mA?

    I have questions related to learning cycle can I ask here or should I open another ticket? If yes the questions are:

    1. What I understand is that we can do learning cycle without bqstudio and EV2400 but in this case we will have to do the cycle for every product individually. Or, we can simply use bqstudio and EV2400, generate golden image just once and upload the image for all our products. Right? Confirm if my understanding is correct.
    2. The first steps in leaning is to discharge the battery fully and keep it empty for 5 hours. The terminate voltage for our product is 3V, so once the voltage of the battery reaches 3 V, we disconnect the MCU from the battery and keep the battery supplying only the BQ27441 with an average current less 0.1 mA. Does this make BQ27441 enter relax mode and update Qmax? It is mentioned in the data that dv/dt must be less that 4 micro V.

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru 62386 points

    #1:Correct.

    #2: Qmax will update after two OCV measurements with passed charge in between covering a DOD change of 0.9. Several limitations apply (e.g. temperature, flat zone OCV). The basic learning cycle is to start with a fully relaxed, almost empty cell, charge to full (as per the cell datasheet recommendations), let it relax, discharge with C/5 down to 3000mV, let it relax.