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BQ25890: How to charge the 4.35V battery with BQ25890?

FrankXu
Genius 3500 points
Part Number: BQ25890
Other Parts Discussed in Thread: BQ25895M, BQ25606

Hi,

The Default Battery Charge Voltage of BQ25890 is 4.2V.

Question1:  How to charge a 4.35V battery? Just change the VREG (Charge Voltage Limit) in REG06 to 4.35V? Is that enough?

Question2: But, since the VREG must be written with I2C and in my system, the CPU may be powered down when charging. In this situation, the charge voltage would be the default 4.2V. The battery cannot be fully charged. Will that damage the battery if the charge voltate is 4.2V not 4.35V, for a 4.35V battery? Or will that shorten the life of the battery?

Question3： Is there any way to make the 4.35V charge voltage without software programing? Or, is there any other Power Maganement Chip in TI, with a default charge voltage of 4.35V?

Thank you.

  • 0
    TI__Guru**** 166626 points

    Frank,

    Regarding 1, yes.

    Regarding 2, stopping charge at 4.2V instead of 4.35V results in lower capacity and therefore shorter battery operating time. Actually, charging to a lower voltage lengthens battery life.  

    Regarding 3, TI has a 3-A standalone charge, BQ25606, that has VSET pin which can be configured for VBATREG= 4.35V.  Alternatively, there is the BQ25895M which is default 4.35V.  It is pin to pin with the BQ25890 but it's OTG boost output, if enabled, is at PMID not VBUS like BQ25890.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Genius 3500 points

    Hi Jeff,

          Thank you so much for your help!

    Frank