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BQ24610: TS resistor network setting from 1degC to 44degC

S.Satoshi
Guru 21685 points
Part Number: BQ24610
Other Parts Discussed in Thread: BQ24160,

Hi,

Now the customer consider to use bq24160 and they hope to set TCOLD = 1degC and TCUT_OFF = 44degC with 103AT NTC. They tried to calculate RT1 and RT2 with attached spread sheet but it seems that delta from TCOLD to TCUT_OFF can't be set less than 45degC. Is my understanding correct? Actually I also tried to use "bq246xx Calculation Tool V1.5 (Rev. D)" and confirmed that the calculated resistance of RT2 show negative value. So please let me ask following question.

  1. Can we set TCOLD = 1degC and TCUT_OFF = 44degC with 103AT NTC at bq24610?
  2. If the answer for #1 is No, do you have any idea or solution to achieve this requirement?

180702 bq24610 TS_1to44degC setting.xlsx

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Genius 10240 points
    Satoshi San,

    The RT2 is in parallel with TS. The equivalent resistance RT2 // R_TS would be lower than either RT2 or R_TS. Higher value of RT2 has less effect to reduce the parallel resistance. What happen here is that the RT2 can't bring the RT2 // R_TS lower when RT2 goes to infinity. In this application case, you can use RT1 and TS and not use RT2. The network is a simple voltage divider with RT1 and TS. With RT1 = 9.61 kohm, the VTS = 73.0% Vref @ 1C and VTS = 34.5% Vref @ 44C. You can change RT1 to make the best tradeoff . Please be advised that he accuracy of TS also has impact to the measured temperature.

    Regards,

    Eric