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BQ21040: Bias battery NTC from other device

Dave9
Prodigy 20 points
Part Number: BQ21040

Hello,

I am planning to use BQ21040 to charge a battery. This battery has an internal NTC I will connect to the TS pin.

I would like to use the same NTC to do another temperature measurement.

As I see in the datasheet, BQ21040 biases the NTC with a current source, 50uA if charging, 30uA if charge disabled (I guess when temp>45C).

I can work with it but, what happens in the TS pin if Vin<4.45V?

If ntc is not biased in that case, can I bias the NTC from the other device? (I would be setting a voltage on TS pin then)

Is there any other situation where BQ21040 does not bias the NTC?

Regards,

Dave

  • 0
    TI__Guru* 75786 points

    Hi Dave

    I do not recommend applying external current to TS pin it will power internal circuits and results will be unreliable.  But a MOSFET could be used to disconnect the TS pin from NTC with external circuit.

    Will update you later in the week on conditions that will disable TS.

  • 0 in reply to Bill Johns
    TI__Guru* 75786 points

    Hi Dave

    Following up on other conditions that will disable TS pin current, it is present in almost every condition.  Only UVLO (<3.3V) seems to disable the 50uA current source into 10k resistor.