The MCP73833 cell charger has THERM input, which enables the chip to monitor the temperature of a battery:

By choosing appropriate R_T1 and R_T2 values (depending on NTC thermistor parameters), the designer can adjust allowed operating temperatures (e.g. from 0C to 50C), which is described in the datasheet:

So far, so good. But solving above equations for R_T1 and R_T2 requires calculating NTC resistance two times, then calculating quadratic equation parameters (A,B,C), then calculating R_T2 and finally calculating R_T1. It gets really annoying after second iteration (since you chose wrong thermistor R_0 and R_T1 is negative...):

So I quickly created a spreadsheet document that calculates all that stuff automatically - just put in the thermistor parameters (R_0 and B) and T_cold and T_hot.

Now choosing the right NTC and resistors should be easy :)

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Please share your spread sheet. Thanks

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