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Open Menu / Documentation / hwmon / lm75
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Kernel driver lm75
==================

Supported chips:
  * National Semiconductor LM75
    Prefix: 'lm75'
    Addresses scanned: I2C 0x48 - 0x4f
    Datasheet: Publicly available at the National Semiconductor website
               http://www.national.com/
  * Dallas Semiconductor DS75
    Prefix: 'lm75'
    Addresses scanned: I2C 0x48 - 0x4f
    Datasheet: Publicly available at the Dallas Semiconductor website
               http://www.maxim-ic.com/
  * Dallas Semiconductor DS1775
    Prefix: 'lm75'
    Addresses scanned: I2C 0x48 - 0x4f
    Datasheet: Publicly available at the Dallas Semiconductor website
               http://www.maxim-ic.com/
  * Maxim MAX6625, MAX6626
    Prefix: 'lm75'
    Addresses scanned: I2C 0x48 - 0x4b
    Datasheet: Publicly available at the Maxim website
               http://www.maxim-ic.com/
  * Microchip (TelCom) TCN75
    Prefix: 'lm75'
    Addresses scanned: I2C 0x48 - 0x4f
    Datasheet: Publicly available at the Microchip website
               http://www.microchip.com/

Author: Frodo Looijaard <frodol@dds.nl>

Description
-----------

The LM75 implements one temperature sensor. Limits can be set through the
Overtemperature Shutdown register and Hysteresis register. Each value can be
set and read to half-degree accuracy.
An alarm is issued (usually to a connected LM78) when the temperature
gets higher then the Overtemperature Shutdown value; it stays on until
the temperature falls below the Hysteresis value.
All temperatures are in degrees Celsius, and are guaranteed within a
range of -55 to +125 degrees.

The LM75 only updates its values each 1.5 seconds; reading it more often
will do no harm, but will return 'old' values.

The LM75 is usually used in combination with LM78-like chips, to measure
the temperature of the processor(s).

The DS75, DS1775, MAX6625, and MAX6626 are supported as well.
They are not distinguished from an LM75. While most of these chips
have three additional bits of accuracy (12 vs. 9 for the LM75),
the additional bits are not supported. Not only that, but these chips will
not be detected if not in 9-bit precision mode (use the force parameter if
needed).

The TCN75 is supported as well, and is not distinguished from an LM75.

The LM75 is essentially an industry standard; there may be other
LM75 clones not listed here, with or without various enhancements,
that are supported.

The LM77 is not supported, contrary to what we pretended for a long time.
Both chips are simply not compatible, value encoding differs.