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Original question:

BQ24072: CE pin logic selection at Battery mode

BQ24072: PGOOD pin working

Jagan K
Prodigy 120 points
Part Number: BQ24072

Hi,
 We have been using the Bq24072RGTR in our project as a charger for charging 4.2V Li-ion battery. We are using a 5V as input supply which will pass through a Schottky diode before entering the IC, so the voltage that enters the IC will be around 4.35 - 4.5 V. 

We have connected the PGOOD pin to our Interrupt pin of MC and During the full charge of the battery we are facing a strange behavior at PGOOD pin, like it its toggling between HIGH/LOW and getting the interrupt. While checking the datasheet of the BQ24072, we found a condition for the PGOOD pin status indicator in the below image. Based on the below condition, it seems when the battery reaches 4.2 V which adds with Vin(DT) is 130 mv which will be 4.33V. If the Vin is less than the Vbat+Vin(Dt), PGOOD is LOW.

So we planned to disable the CE pin at a certain level of the battery and stops it reaching the full battery to stop this toggling of PGOOD pin. This cycle of disabling the CE pin will be keep on repeating during every charging, will these kind of disabling CE will cause any problem in future?



Thanks
Jagan K

  • 0
    TI__Expert 8245 points

    Hi Jagan,

    I don't expect this to cause any long term issues in the future. The only tradeoff here is by disabling the CE pin before 4.2V you will obviously be not achieving the full capacity of the battery. The good news here is that purposely restricting the charging range of the cell will allow it to degrade slower over time.

    One question though, how do you know when to disable CE? Are you waiting until a certain voltage level gets reported or are you using a gauge and waiting until a certain SOC?

    Thanks,

    Jackson

  • 0 in reply to Jackson DiGiovanna
    Prodigy 120 points

    Hi Jackson,
        Thanks for your response.
        We will be monitoring the Battery's Voltage using 8-bit ADC. When the battery reaches a certain voltage(i.e battery volt is 4.1V and respective ADC is 4020) then we will be disabling the CE pin.


    Regards,
    Jagan

  • 0 in reply to Jagan K
    TI__Expert 8245 points

    Hi Jagan,

    Sounds good. I dont anticipate any issues here but feel free to reach out if any come up and I will be happy to answer.

    Best Regards,

    Jackson