xref: /openbmc/linux/Documentation/hwmon/lm75.rst (revision 32daa5d7) 
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
97
98    Prefixes: 'tmp100', 'tmp101', 'tmp105', 'tmp112', 'tmp175', 'tmp75', 'tmp75b', 'tmp75c', 'tmp275'
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  * NXP LM75B, PCT2075
123
124    Prefix: 'lm75b', 'pct2075'
125
126    Addresses scanned: none
127
128    Datasheet: Publicly available at the NXP website
129
130	       https://www.nxp.com/documents/data_sheet/LM75B.pdf
131
132               https://www.nxp.com/docs/en/data-sheet/PCT2075.pdf
133
134Author: Frodo Looijaard <frodol@dds.nl>
135
136Description
137-----------
138
139The LM75 implements one temperature sensor. Limits can be set through the
140Overtemperature Shutdown register and Hysteresis register. Each value can be
141set and read to half-degree accuracy.
142An alarm is issued (usually to a connected LM78) when the temperature
143gets higher then the Overtemperature Shutdown value; it stays on until
144the temperature falls below the Hysteresis value.
145All temperatures are in degrees Celsius, and are guaranteed within a
146range of -55 to +125 degrees.
147
148The driver caches the values for a period varying between 1 second for the
149slowest chips and 125 ms for the fastest chips; reading it more often
150will do no harm, but will return 'old' values.
151
152The original LM75 was typically used in combination with LM78-like chips
153on PC motherboards, to measure the temperature of the processor(s). Clones
154are now used in various embedded designs.
155
156The LM75 is essentially an industry standard; there may be other
157LM75 clones not listed here, with or without various enhancements,
158that are supported. The clones are not detected by the driver, unless
159they reproduce the exact register tricks of the original LM75, and must
160therefore be instantiated explicitly. Higher resolution up to 16-bit
161is supported by this driver, other specific enhancements are not.
162
163The LM77 is not supported, contrary to what we pretended for a long time.
164Both chips are simply not compatible, value encoding differs.
165