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BQ76952: T=f(R) temperature calculation

Part Number: BQ76952

Dear team,

Customer want to use the 0x70,0x74, 0x76 read value from BQ76952 by MCU, and calculate the temperature by developing their own program according to the values.

Could you share the formula for TS resistor and temperature transition?

Here is the customer's temperature resistors table.

    204470,    193260,    182760,    172910,    163650,    154940,    146740,    139020,    131730,    124870, // -40 ~ -31  ( 0 -  9)

    118390,    112280,    106510,    101070,    95932,      91083,     86505,     82182,     78100,     74245,// -30 ~ -21  (10 - 19)

    70603,    67163,    63911,    60838,    57932,    55183,    52583,    50123,    47794,    45588,

    43499,    41518,    39641,    37861,   36172,    34569,    33047,    31601,    30227,    28921,

    27680,    26499,    25375,    24305,    23286,    22316,    21391,    20510,    19670,    18869,

    18104,    17375,    16679,    16014,    15379,    14773,    14194,    13640,    13111,    12605,

    12122,    11659,    11217,    10793,    10388,    10000,     9629,     9273,     8933,     8606,

    8294,      7994,     7707,       7432,    7168,        6915,      6672,     6439,    6216,    6001,

    5795,    5598,    5408,    5226,    5050,               4882,    4720,    4565,    4415,    4271,

    4133,    4000,    3872,    3749,    3630,    3516,    3406,    3300,    3198,    3099,

    3004,    2913,    2825,    2739,    2657,    2578,    2502,    2428,    2357,    2288,

    2221,    2157,    2095,    2035,    1977,    1921,    1867,    1814,    1764,    1714,

    1667,    1621,    1577,    1533,    1492,    1451,    1412,    1374,    1338,    1302,

    1268,    1234,    1202,    1171,    1140,    1111,    1082,    1054,    1027,    1001,

    976,    951,    928,    905,    882,    860,    839,    819,    799,    780,      //  100 ~ 109 (140 - 149)

    761,    743,    725,    708,    692,    675,    660,    645,    630,    616,     //  110 ~ 119 (150 - 159) 

    602,    588,    575,    563,    550,    538,

  • Hi Rachel,

    The values read from 0x70,0x74, 0x76 are the temperatures calculated by the BQ76952 polynomial (using the coefficients input into the calibration registers). We cannot share the formula that is used because it is private. 

    If they want to calculate the temperature using their MCU, they can read the raw ADC counts from the DASTATUS registers.

    Best regards,

    Matt

  • Hi Matt,

    Thank you for the reply.

    How they use the raw ADC counts to calculate the temperature?

    From my understanding:

    1. Use the raw ADC counts to calculate the detected voltage as below.

    2. The  related voltage is the marked input value, then we can calculate the corresponding resistance value(RTS1, RTS2, RTS3).

    3. According to the their own "Temperature vs Resistance" table to find the related temperature.

    Am I right?

  • Hi Rachel,

    That is correct. However, the 500 ohm and 18k resistors values do vary from part to part. This is trimmed for the measurements using the TI polynomial.

    Matt

  • Hi Matt,

    I got it.

    Thank you so much for your timely and efficient support.