BQ25120A: NTC management

William Maire

Part Number: BQ25120A

Dear Sir or Madam,

We are currently using the BQ25120A in order to manage the charge of our battery. In order to achieve it properly, we'd like to cut the charge when the battery temperature is under or above a certain voltage.

We used the formula given in the datasheet to compute R(Hi) and R(Lo). It worked well when we defined a minimum temperature of 0°C and a maximum temperature of 40°C. But we'd like to set a minimum temperature of 10°C. In this case, the value of R(LO) become negative.

Do you have any explanation about it ?

Have a nice day,

Kind regards,

William.

11 months ago

0 Juan Ospina 11 months ago

TI__Genius 13735 points

Hi William,

Certain configurations may not be possible depending on the NTC resistance and Beta value. What resistance value (at 25C) and Beta value does your NTC have?

Best Regards,

Juan Ospina

0 William Maire 11 months ago in reply to Juan Ospina

Prodigy 250 points

Hi Juan,

Thanks for the feedback.

I do understand, we have a resistance value of 10kOhm at 25°C and the Beta is equal to 3435.

Have a nice day,

William

0 Juan Ospina 11 months ago in reply to William Maire

TI__Genius 13735 points

Hi William,

With the provided NTC Characteristics it will be impossible to achieve a Max temperature of 40°C and a Min temperature of 10°C. This is too narrow a range for the curvature of the NTC function even with external compensation. In order to achieve this range it would be necessary to select an NTC of a higher Beta value.

Best Regards,

Juan Ospina

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BQ25120A: NTC management