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BQ21062: control for LiFePO4

PAN-M
Mastermind 8375 points
Part Number: BQ21062
Other Parts Discussed in Thread: BQ25071, , BQ21061, BQ25155

Dear team,

Please teach me the control method of I2C when I charge LiFePO4 by this device.
I think;
- Set peak voltage (OVCH:bq25071 charge profile)
- charge start
- polling CHRG_CV_STAT register
- if active, stop charge.

Regards,
PAN-M

  • 0
    TI__Mastermind 23410 points

    Hi PAN-M,

    The BQ21062 will be able to charge on startup if the device is configured correctly. You can reference the BQ25155 Setup Guide Tool for setting peak voltage and starting charge as well as the functions that can help poll registers and stop charge. The only difference between the BQ25155 is the BQ21061 does not have the ADC feature. 

  • 0 in reply to Anthony P Pham
    Mastermind 8375 points

    Hi,

    I think that a Co-based charge profile and the charge profiles of LiFePO4 are different.
    Please refer to a profile of bq25071.
    When the big difference is if arrives at voltage peak (OVCH), it stop CC and a point waiting to become VOUT(REG).
    In the Co-based Li-Ion, changed to CV by this point, and charge current waits to become the set point, stops by a timer.
    When I want to make a profile same as bq25071, in bq21062, I know that it was changed to CV and think that I stop charge.
    Is this correct?

    Regards,
    PAN-M

  • 0 in reply to PAN-M
    TI__Mastermind 23410 points

    Hi,

    There is no way to disable the CV phase, unfortunately but we can control charge.

    You can disable the termination phase by setting the TERM_DISABLE bit in the TERMCTRL register at 0x15. All charge control will then be entirely I2C controlled. You can read the STAT0 register to see when CV loop becomes active. The CV loop will become active you can disable charging and also reconfigure the battery regulation voltage to the desired battery regulation voltage and current. After a set time to let the battery relax, you can enable charging again at the lower current but do note the current will taper to the termination current (which is set to at max 30% charge current). 

    This may be a bit less accurate to do without an ADC to measure the charge current or battery voltage. I recommend the BQ25155 here if possible, you'll be able to measure the battery voltage and charge current. Being able to monitor those values allows you to more accurately adjust the current that would be approaching termination and see when the profile is complete. The BQ25155 is pin to pin with the BQ21062 and has the additional ADC. 

    I'll see about finding some written code to provide for this purpose. 

  • 0 in reply to Anthony P Pham
    Mastermind 8375 points

    Thank you for answer,

    In addition, If I have any question, I will open another thread.

    PAN-M