LXR linux/Documentation/hwmon/ntc

   1Kernel driver ntc_thermistor
   2============================
   3
   4Supported thermistors from Murata:
   5
   6* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473,
   7  NCP15WL333, NCP03WF104, NCP15XH103
   8
   9  Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473',
  10  'ncp15wl333', 'ncp03wf104', 'ncp15xh103'
  11
  12  Datasheet: Publicly available at Murata
  13
  14Supported thermistors from EPCOS:
  15
  16* EPCOS NTC Thermistors B57330V2103
  17
  18  Prefixes: b57330v2103
  19
  20  Datasheet: Publicly available at EPCOS
  21
  22Other NTC thermistors can be supported simply by adding compensation
  23tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
  24
  25Authors:
  26
  27        MyungJoo Ham <myungjoo.ham@samsung.com>
  28
  29Description
  30-----------
  31
  32The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor
  33that requires users to provide the resistance and lookup the corresponding
  34compensation table to get the temperature input.
  35
  36The NTC driver provides lookup tables with a linear approximation function
  37and four circuit models with an option not to use any of the four models.
  38
  39Using the following convention::
  40
  41   $    resistor
  42   [TH] the thermistor
  43
  44The four circuit models provided are:
  45
  461. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0::
  47
  48     [pullup_uV]
  49         |    |
  50        [TH]  $ (pullup_ohm)
  51         |    |
  52         +----+-----------------------[read_uV]
  53         |
  54         $ (pulldown_ohm)
  55         |
  56        -+- (ground)
  57
  582. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)::
  59
  60     [pullup_uV]
  61         |
  62        [TH]
  63         |
  64         +----------------------------[read_uV]
  65         |
  66         $ (pulldown_ohm)
  67         |
  68        -+- (ground)
  69
  703. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0::
  71
  72     [pullup_uV]
  73         |
  74         $ (pullup_ohm)
  75         |
  76         +----+-----------------------[read_uV]
  77         |    |
  78        [TH]  $ (pulldown_ohm)
  79         |    |
  80        -+----+- (ground)
  81
  824. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)::
  83
  84     [pullup_uV]
  85         |
  86         $ (pullup_ohm)
  87         |
  88         +----------------------------[read_uV]
  89         |
  90        [TH]
  91         |
  92        -+- (ground)
  93
  94When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
  95pulldown_ohm, and connect should be provided. When none of the four models
  96are suitable or the user can get the resistance directly, the user should
  97provide read_ohm and _not_ provide the others.
  98
  99Sysfs Interface
 100---------------
 101
 102=============== == =============================================================
 103name               the mandatory global attribute, the thermistor name.
 104=============== == =============================================================
 105temp1_type      RO always 4 (thermistor)
 106
 107temp1_input     RO measure the temperature and provide the measured value.
 108                   (reading this file initiates the reading procedure.)
 109=============== == =============================================================
 110
 111Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.
 112