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BQ24040: Supported thermistor for TS function at new JEITA 45degree threshold

Francesco Mazzei
Prodigy 40 points
Part Number: BQ24040
Other Parts Discussed in Thread: BQ24090

Hello TI community!

The TS function for the BQ24040/5 is designed to follow the new JEITA temperature standard for Li-Ion and Li-Po batteries. In my application, the battery has to stop charging when reaching 45degree temperature.

By using the thermistor suggested on datasheet (SEMITEC 103AT-2 or Mitsubishi TH05-3H103F, a 10K NTC with beta=3370), considering that TS feature is implemented using an internal 50μA current source to bias the thermistor, I reach the defined Hot shutdown of 178mV with a R=3.5K. According to the RT table (RTﾃﾞｰﾀTH05.xls (mmc.co.jp)) this value is at 55 degrees C, which is not acceptable.

I found a 6K8 thermistor that has a Rnom=3.5K at 40 degree - Part No NTCG104BH682JT1.. See extract of the RT tabel below:

34 4.289 4.569 4.855 4047 -1.5 1.4
35 4.103 4.377 4.657 4048 -1.5 1.5
36 3.927 4.194 4.468 4049 -1.5 1.5
37 3.759 4.02 4.288 4051 -1.6 1.5
38 3.599 3.854 4.116 4052 -1.6 1.6
39 3.447 3.696 3.952 4053 -1.7 1.6
40 3.303 3.545 3.796 4055 -1.7 1.7
41 3.165 3.401 3.646 4056 -1.7 1.7
42 3.033 3.264 3.503 4057 -1.8 1.7
43 2.908 3.133 3.367 4058 -1.8 1.8
44 2.788 3.008 3.236 4060 -1.9 1.8
45 2.674 2.888 3.112 4061 -1.9 1.9
46 2.566 2.774 2.993 4062 -1.9 1.9
47 2.462 2.666 2.879 4063 -2 2
48 2.363 2.562 2.77 4064 -2 2
49 2.269 2.462 2.665 4066 -2.1 2
50 2.179 2.367 2.565 4067 -2.1 2.1
51 2.093 2.276 2.47 4068 -2.2 2.1
52 2.01 2.189 2.378 4069 -2.2 2.2
53 1.932 2.106 2.291 4070 -2.2 2.2
54 1.857 2.027 2.207 4071 -2.3 2.3
55 1.785 1.951 2.127 4072 -2.3 2.3

This would mean that the Hot shutdown voltage of 178mV is reached at a temperature of 40 degree rather than 55.

Can I use this thermistor with BQ24040?

Thanks in advance,

Francesco

  • 0
    TI__Mastermind 31550 points

    Hi Francesco, 

    Yes the 6.8k thermistor you reference can be used with the BQ24040. Although, be aware of the potential impact on the rest of the device temperature thresholds. The higher beta (beta = 4100) of the NTCG104BH682JT should allow you to keep the cold threshold around 0C if desired. You will want to calculate the temperatures associated with the defined JEITA standard V-TS thresholds to confirm the thermistor meets the temperature specifications for your application. 

    For reference the hot temperature voltage regulation range is 178mV to 278 mV. Cold temperature current regulation occurs for V-TS 790 mV to 1.23 V with cold shutdown occurring for V-TS of 1.23 V to 1.6 V. If you would like confirmation that this thermistor works for your full desired temperature range please provide your desired operational temperature range and the thermistor's full RT table.

    Also, if you are looking for a device with a 0-45C temperature window that does not follow the JEITA standard please consider the BQ24090. This device is the non JEITA version of the BQ24040.   

    Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 40 points

    Hi Garrett,

    Thanks for the detailed answer. The operating range is 0-45degree and attached is the full RT table for the thermistor NTCG104BH682JT1.ntcg104bh682jt1.csv

    Can you please confirm this will work for the temperature range above?

    Regards,

    Francesco

  • +1 in reply to Francesco Mazzei
    TI__Mastermind 31550 points

    Hi Francesco,

    Thank you for providing the full RT table for the thermistor in question. The operating range using this thermistor will be -1C to 40C with hot temperature voltage regulation from 30C to 40C and cold temperature current regulation from -1C to 7C. 

    Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 40 points

    Thanks for confirming this Garrett!

    Kind Regards,

    Francesco