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BQ25600D: Minus calculation result of R1/R2 around NTC

TAKASHI SODA
Prodigy 190 points
Part Number: BQ25600D

Dear In-charge person.

About BQ25600D, we are considering R1/R2 around NTC, with referring to section 8.3.7.5.

As result of calculation, we obtain negative value for R2.
Please let me know what above result mean.
Does the result indicate that our assumptions cannot be realized?
Our assumption details are as following.
   NTC:NCP03XH103D05RL (10kΩ / 3434 @25/85℃)
   T1:3℃
   T5:43℃
Thanks and Best Regards.
  • +1
    TI__Guru*** 148915 points

    Hi Takashi,

    A negative value means that the temp range and/or thermistor Beta are not compatible with the charger's VTx percentages.  You have the following options:

    1. Try to find a different thermistor with different Beta that works.

    2.  Use a gauge and ADC IC and host processor instead of charger to monitor battery temp and control charge turn off. 

    2. Change T1=2℃ and T5=46℃ as this seems to be the max for your thermistor.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 190 points

    Hi Jeff 

    Thnaks for your replying.

    We will cosider with refering your idea.

    Thanks and Best Regards

    Takashi SODA