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BQ21040: Using a Thermistor with a Different Beta β

Victor Salomon
Expert 3910 points
Part Number: BQ21040

Hello,

I was wondering if a thermistor with a beta parameter β = 3380 K (such as Murata's NCP15XH103F03RC) could be used - the E2E thread below suggests that both β = 3370 and β = 3435 could be used, which are the Mitsubishi and SEMITEC thermistors respectively that are recommended on the datasheet.

Additionally, if a beta parameter β = 3380 K is acceptable, is there any considerations that should be taken into account?

  • 0
    TI__Guru* 75656 points
    Hi Victor
    The bq21040 will trip cold at 1.25V and trip hot at 0.275V on TS pin. Current out of the TS pin is 50uA so resistance Cold needs to be 25k ohm and Hot needs to be 5500 ohms. More than 25k will trip cold, Less than 5500 will trip hot. This is using typical values.
    For a 10k ohm (25C) NTC:
    1.) B=3380, Hot 41C R=5613, Cold 3C R=24.67k ohms
    2.) B=3370, Hot 41C R=5623, Cold 3C R=24.60k ohms
    3.) B=3435, Hot 41C R=5561, Cold 4C R=23.94k ohms

    The typical target temp range is 0C to 45C and above NTC B will give good results.