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BQ25638: Force TS Zone

Joe Paolino
Intellectual 470 points
Part Number: BQ25638
Other Parts Discussed in Thread: BQ27Z746,

Tool/software:

Hello,

I'm designing an LFP charging circuit with the BQ25638 and the BQ27Z746.  The BQ27Z746 will be monitoring the cell temperature and supplying appropriate values for VREG and ICHG.  I don't need an additional thermistor connected to the BQ25638, but I would like to take advantage of its ability to regulate voltage below 3.5V as shown in Figure 8-3 of the datasheet.

If I place a fixed resistor divider on the TS pin to force the BQ25638 into Pre-Warm or Pre-Cool permanently are there any unintended consequences to this action?

Thank you,

Joe

  • 0
    TI__Guru 57611 points

    Hi Joe,

    In this case, the TS_STAT will be detected as Pre-Warm or Pre-Cool all the time.

    BTW, Most of the customers who use both charger and gauge write host software to make continuous gauge measurements and then send I2C commands to change the charger operation if necessary.

    Thanks,

    Ning

  • 0 in reply to Ning T
    Intellectual 470 points

    Thanks, Ning.  The intent of forcing the charger into Pre-Warm or Pre-Cool is that it would permit a VREG lower than 3.5V.  In TS_Normal, 3.5V is the minimum setting if I understand the part correctly.  Are there any negative consequences to locking the measured temperature?

  • +1 in reply to Joe Paolino
    TI__Guru 57611 points

    Hi,

    In order to force pre-warm or pre-cool status, (VTS/VREGN)% need to be in the range below. The charger does not monitor thermistor temperature directly. It should be fine for the charger. Please check if the charging parameter values are suitable to the specific batteries in the application.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 470 points

    Thanks for your help, Ning.

    Joe