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BQ25895: Reprogram Default Values

Kamron Fazel
Prodigy 60 points
Part Number: BQ25895
Other Parts Discussed in Thread: BQ25606

Hi,

I find the BQ25895 to work well for our application (low cost and 5A charge rate max) except when it loses power, the registries of interest (e.g., battery charge current and input current rate and disable ILIM pin) go back to default values.    The plan is to only program the BQ25895 once for its life even if batteries are changed out.  So given the reset of registries on power loss, this chip does not meet our need.

Is it possible for TI to produce a chip at the 10-30k/yr volume with the default value registers tailored to our application?  Or is there a way for us to do it?

Thanks,

Kamron

  • 0
    TI__Guru**** 166396 points
    Kamron,

    The bq25895 is designed to be a host controlled charger. Returning to the I2C default values after power down is a charging safety feature. Unfortunately, changing the default values requires TI to release a new version of the IC.

    We do not have a standalone version charger capable of 5A. However, you could parallel two bq25606 3-A standalone chargers, connecting their BAT pins. I suggest adding a small 0.1ohm power resistor in series with the BAT pin of one of the chargers so that it terminates well before the other charger in order to prevent oscillating between the two chargers as they both try to terminate at the same time.
  • 0 in reply to Jeff F
    Prodigy 60 points
    Thanks Jeff for the reply and suggestion. Do you know if there is an application note on paralleling charger ICs?

    Do you know the cost to release a new version of the IC with the defaults changed? Or is it possible to change them on my end?
  • 0 in reply to Kamron Fazel
    TI__Guru**** 166396 points

    I wrote a paper on paralleling chargers here.  One charger is the master and the other the slave.  You would want to connect the two input pins to input power and the two BAT pins to the battery, not the cascading option.  You cannot connect the two SYS pins so the SYS output of one charger will be the only system rail.  The two main concerns are termination, as mentioned above, and VINDPM on the VBUS lines.  You want to set the VINDPM of one of the chargers below the other so that they will not oscillate.

    Unfortunately, the cost to release a new charger version is higher than the revenue from your application.  The default values are not user re-programmable.

  • 0 in reply to Jeff F
    Prodigy 60 points
    Thanks for your assistance!