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BQ2004: RT1/RT2 Value

Yoshinobu Kagawa
Expert 2030 points
Part Number: BQ2004

The thermistor to be set in BQ2004 is planned to be 103KAT-4/SEMIETC.
The heat dissipation and heat time constants are different from the 103AT-2/SEMIETC described in DV2004L1, what values ​​should be set for RT1 and RT2?

Best regards,

Kagawa

  • 0
    TI__Mastermind 24075 points

    Hi Kagawa,

       Recommended values for VLTF = 0.4*VCC, VTCO = in range of 0.2*VCC to 0.4*VCC and VHTF = [(1/4 ∗ VLTF) + (3/4 ∗ VTCO)]. The VLTF voltage should be calculated based off of using the resistance of your selected thermistor that corresponds to the lowest temperature range to allow charging. Similarly VHTF should be calculated based off of using the resistance of your selected thermistor that corresponds to the highest temperature range to allow charging.

  • 0 in reply to Kedar Manishankar
    Expert 2030 points

    Hi Kedar-san,

    To bq2004 I would like to use 103AT-4/SEMIETC in the range of -10 degree to 60 degree. How should I calculate the resistance value RT1 and 2?

    Best regards,

    Kagawa

  • 0 in reply to Yoshinobu Kagawa
    TI__Mastermind 24075 points

    Hi Kagawa-san,

       You have to equate the voltage from the resistor divider to the values of LTF, HTF, and TCO shown above. To do so you use the resistance of the thermistor at the respective temperature and back calculate to find RT1 and RT2 (you can fix RT1 or RT2 and calculate for the other).