linux/Documentation/hwmon/ntc_thermistor
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   1Kernel driver ntc_thermistor
   2=================
   3
   4Supported thermistors from Murata:
   5* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333
   6  Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333'
   7  Datasheet: Publicly available at Murata
   8
   9Supported thermistors from EPCOS:
  10* EPCOS NTC Thermistors B57330V2103
  11  Prefixes: b57330v2103
  12  Datasheet: Publicly available at EPCOS
  13
  14Other NTC thermistors can be supported simply by adding compensation
  15tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
  16
  17Authors:
  18        MyungJoo Ham <myungjoo.ham@samsung.com>
  19
  20Description
  21-----------
  22
  23The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor
  24that requires users to provide the resistance and lookup the corresponding
  25compensation table to get the temperature input.
  26
  27The NTC driver provides lookup tables with a linear approximation function
  28and four circuit models with an option not to use any of the four models.
  29
  30The four circuit models provided are:
  31
  32        $: resister, [TH]: the thermistor
  33
  34 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0
  35
  36   [pullup_uV]
  37       |    |
  38      [TH]  $ (pullup_ohm)
  39       |    |
  40       +----+-----------------------[read_uV]
  41       |
  42       $ (pulldown_ohm)
  43       |
  44      --- (ground)
  45
  46 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)
  47
  48   [pullup_uV]
  49       |
  50      [TH]
  51       |
  52       +----------------------------[read_uV]
  53       |
  54       $ (pulldown_ohm)
  55       |
  56      --- (ground)
  57
  58 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0
  59
  60   [pullup_uV]
  61       |
  62       $ (pullup_ohm)
  63       |
  64       +----+-----------------------[read_uV]
  65       |    |
  66      [TH]  $ (pulldown_ohm)
  67       |    |
  68      -------- (ground)
  69
  70 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)
  71
  72   [pullup_uV]
  73       |
  74       $ (pullup_ohm)
  75       |
  76       +----------------------------[read_uV]
  77       |
  78      [TH]
  79       |
  80      --- (ground)
  81
  82When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
  83pulldown_ohm, and connect should be provided. When none of the four models
  84are suitable or the user can get the resistance directly, the user should
  85provide read_ohm and _not_ provide the others.
  86
  87Sysfs Interface
  88---------------
  89name            the mandatory global attribute, the thermistor name.
  90
  91temp1_type      always 4 (thermistor)
  92                RO
  93
  94temp1_input     measure the temperature and provide the measured value.
  95                (reading this file initiates the reading procedure.)
  96                RO
  97
  98Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.
  99