5 * Analog Devices ADT7473
7 Addresses scanned: I2C 0x2C, 0x2D, 0x2E
8 Datasheet: Publicly available at the On Semiconductors website
9 * Analog Devices ADT7475
11 Addresses scanned: I2C 0x2E
12 Datasheet: Publicly available at the On Semiconductors website
13 * Analog Devices ADT7490
15 Addresses scanned: I2C 0x2C, 0x2D, 0x2E
16 Datasheet: Publicly available at the On Semiconductors website
21 Darrick J. Wong (documentation)
28 This driver implements support for the Analog Devices ADT7473, ADT7475 and
29 ADT7490 chip family. The ADT7473 and ADT7475 differ only in minor details.
30 The ADT7490 has additional features, including extra voltage measurement
31 inputs and PECI support. All the supported chips will be collectively
32 designed by the name "ADT747x" in the rest of this document.
34 The ADT747x uses the 2-wire interface compatible with the SMBus 2.0
35 specification. Using an analog to digital converter it measures three (3)
36 temperatures and two (2) or more voltages. It has four (4) 16-bit counters
37 for measuring fan speed. There are three (3) PWM outputs that can be used
40 A sophisticated control system for the PWM outputs is designed into the
41 ADT747x that allows fan speed to be adjusted automatically based on any of the
42 three temperature sensors. Each PWM output is individually adjustable and
43 programmable. Once configured, the ADT747x will adjust the PWM outputs in
44 response to the measured temperatures without further host intervention.
45 This feature can also be disabled for manual control of the PWM's.
47 Each of the measured inputs (voltage, temperature, fan speed) has
48 corresponding high/low limit values. The ADT747x will signal an ALARM if
49 any measured value exceeds either limit.
51 The ADT747x samples all inputs continuously. The driver will not read
52 the registers more often than once every other second. Further,
53 configuration data is only read once per minute.
55 Chip Differences Summary
56 ------------------------
60 * system acoustics optimizations (not implemented)
67 * 1 Imon input (not implemented)
68 * PECI support (not implemented)
69 * 2 GPIO pins (not implemented)
70 * system acoustics optimizations (not implemented)
75 The ADT747x has a 10-bit ADC and can therefore measure temperatures
76 with a resolution of 0.25 degree Celsius. Temperature readings can be
77 configured either for two's complement format or "Offset 64" format,
78 wherein 64 is subtracted from the raw value to get the temperature value.
80 The datasheet is very detailed and describes a procedure for determining
81 an optimal configuration for the automatic PWM control.
86 The driver exposes two trip points per PWM channel.
88 point1: Set the PWM speed at the lower temperature bound
89 point2: Set the PWM speed at the higher temperature bound
91 The ADT747x will scale the PWM linearly between the lower and higher PWM
92 speed when the temperature is between the two temperature boundaries.
93 Temperature boundaries are associated to temperature channels rather than
94 PWM outputs, and a given PWM output can be controlled by several temperature
95 channels. As a result, the ADT747x may compute more than one PWM value
96 for a channel at a given time, in which case the maximum value (fastest
97 fan speed) is applied. PWM values range from 0 (off) to 255 (full speed).
99 Fan speed may be set to maximum when the temperature sensor associated with
100 the PWM control exceeds temp#_max.
105 The nVidia binary driver presents an ADT7473 chip via an on-card i2c bus.
106 Unfortunately, they fail to set the i2c adapter class, so this driver may
107 fail to find the chip until the nvidia driver is patched.