xref: /openbmc/linux/Documentation/hwmon/lm75.rst (revision ee65728e) 
1Kernel driver lm75
2==================
3
4Supported chips:
5
6  * National Semiconductor LM75
7
8    Prefix: 'lm75'
9
10    Addresses scanned: I2C 0x48 - 0x4f
11
12    Datasheet: Publicly available at the National Semiconductor website
13
14	       http://www.national.com/
15
16  * National Semiconductor LM75A
17
18    Prefix: 'lm75a'
19
20    Addresses scanned: I2C 0x48 - 0x4f
21
22    Datasheet: Publicly available at the National Semiconductor website
23
24	       http://www.national.com/
25
26  * Dallas Semiconductor (now Maxim) DS75, DS1775, DS7505
27
28    Prefixes: 'ds75', 'ds1775', 'ds7505'
29
30    Addresses scanned: none
31
32    Datasheet: Publicly available at the Maxim website
33
34	       https://www.maximintegrated.com/
35
36  * Maxim MAX6625, MAX6626, MAX31725, MAX31726
37
38    Prefixes: 'max6625', 'max6626', 'max31725', 'max31726'
39
40    Addresses scanned: none
41
42    Datasheet: Publicly available at the Maxim website
43
44	       http://www.maxim-ic.com/
45
46  * Microchip (TelCom) TCN75
47
48    Prefix: 'tcn75'
49
50    Addresses scanned: none
51
52    Datasheet: Publicly available at the Microchip website
53
54	       http://www.microchip.com/
55
56  * Microchip MCP9800, MCP9801, MCP9802, MCP9803
57
58    Prefix: 'mcp980x'
59
60    Addresses scanned: none
61
62    Datasheet: Publicly available at the Microchip website
63
64	       http://www.microchip.com/
65
66  * Analog Devices ADT75
67
68    Prefix: 'adt75'
69
70    Addresses scanned: none
71
72    Datasheet: Publicly available at the Analog Devices website
73
74	       https://www.analog.com/adt75
75
76  * ST Microelectronics STDS75
77
78    Prefix: 'stds75'
79
80    Addresses scanned: none
81
82    Datasheet: Publicly available at the ST website
83
84	       http://www.st.com/internet/analog/product/121769.jsp
85
86  * ST Microelectronics STLM75
87
88    Prefix: 'stlm75'
89
90    Addresses scanned: none
91
92    Datasheet: Publicly available at the ST website
93
94	       https://www.st.com/resource/en/datasheet/stlm75.pdf
95
96  * Texas Instruments TMP100, TMP101, TMP105, TMP112, TMP75, TMP75B, TMP75C, TMP175, TMP275, TMP1075
97
98    Prefixes: 'tmp100', 'tmp101', 'tmp105', 'tmp112', 'tmp175', 'tmp75', 'tmp75b', 'tmp75c', 'tmp275', 'tmp1075'
99
100    Addresses scanned: none
101
102    Datasheet: Publicly available at the Texas Instruments website
103
104	       https://www.ti.com/product/tmp100
105
106	       https://www.ti.com/product/tmp101
107
108	       https://www.ti.com/product/tmp105
109
110	       https://www.ti.com/product/tmp112
111
112	       https://www.ti.com/product/tmp75
113
114	       https://www.ti.com/product/tmp75b
115
116	       https://www.ti.com/product/tmp75c
117
118	       https://www.ti.com/product/tmp175
119
120	       https://www.ti.com/product/tmp275
121
122         https://www.ti.com/product/TMP1075
123
124  * NXP LM75B, PCT2075
125
126    Prefix: 'lm75b', 'pct2075'
127
128    Addresses scanned: none
129
130    Datasheet: Publicly available at the NXP website
131
132	       https://www.nxp.com/documents/data_sheet/LM75B.pdf
133
134               https://www.nxp.com/docs/en/data-sheet/PCT2075.pdf
135
136Author: Frodo Looijaard <frodol@dds.nl>
137
138Description
139-----------
140
141The LM75 implements one temperature sensor. Limits can be set through the
142Overtemperature Shutdown register and Hysteresis register. Each value can be
143set and read to half-degree accuracy.
144An alarm is issued (usually to a connected LM78) when the temperature
145gets higher then the Overtemperature Shutdown value; it stays on until
146the temperature falls below the Hysteresis value.
147All temperatures are in degrees Celsius, and are guaranteed within a
148range of -55 to +125 degrees.
149
150The driver caches the values for a period varying between 1 second for the
151slowest chips and 125 ms for the fastest chips; reading it more often
152will do no harm, but will return 'old' values.
153
154The original LM75 was typically used in combination with LM78-like chips
155on PC motherboards, to measure the temperature of the processor(s). Clones
156are now used in various embedded designs.
157
158The LM75 is essentially an industry standard; there may be other
159LM75 clones not listed here, with or without various enhancements,
160that are supported. The clones are not detected by the driver, unless
161they reproduce the exact register tricks of the original LM75, and must
162therefore be instantiated explicitly. Higher resolution up to 16-bit
163is supported by this driver, other specific enhancements are not.
164
165The LM77 is not supported, contrary to what we pretended for a long time.
166Both chips are simply not compatible, value encoding differs.
167