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BQ51050b NTC Circuit Design

Moritz Heuser
Prodigy 20 points
Other Parts Discussed in Thread: BQ51013A, BQ51013, BQ51050B

Hi,

I have a hard time understanding how to connect the TS Pin with the NTC circuit. In Figure 22 in the DS R2 is connected to some pin/rail I guess and the TS Pin is sensing the voltage dropping at the NTC. So to what pin should I use to pull up the TS pin with R2 (since there is no VSTB Pin like in other components)?

Thank you,

Moritz

  • 0
    TI__Guru* 75976 points

    The resistor R2 in figure 22 (bq51050B Data Sheet) is internal to the device.  It is only shown for a better understanding of the circuit.  The older devices, bq51013 did have a VSTB pin and a 20k external resistor was required. New devices starting with the bq51013A do not require the external resistor.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Great, thank you Bill!

    Just one follow up question to the calculations after figure 22. Why is there R2 with an other value then 20k given? Can it be that the indexes from the calculation and the figure don't match?

    Best Regards,

    Moritz

  • 0 in reply to Moritz Heuser
    TI__Guru* 75976 points

     

    The value for R2 = 7.81k is not accurate for the bq51050B device.  It would be an option for the bq51013.  Equations are correct but the value for R2 is now a fixed 20k.

    We will look at revising this section to reflect the fixed value of R2.