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 ADT7476
15 Addresses scanned: I2C 0x2C, 0x2D, 0x2E
16 Datasheet: Publicly available at the On Semiconductors website
17 * Analog Devices ADT7490
19 Addresses scanned: I2C 0x2C, 0x2D, 0x2E
20 Datasheet: Publicly available at the On Semiconductors website
25 Darrick J. Wong (documentation)
32 This driver implements support for the Analog Devices ADT7473, ADT7475,
33 ADT7476 and ADT7490 chip family. The ADT7473 and ADT7475 differ only in
34 minor details. The ADT7476 has additional features, including extra voltage
35 measurement inputs and VID support. The ADT7490 also has additional
36 features, including extra voltage measurement inputs and PECI support. All
37 the supported chips will be collectively designed by the name "ADT747x" in
38 the rest of this document.
40 The ADT747x uses the 2-wire interface compatible with the SMBus 2.0
41 specification. Using an analog to digital converter it measures three (3)
42 temperatures and two (2) or more voltages. It has four (4) 16-bit counters
43 for measuring fan speed. There are three (3) PWM outputs that can be used
46 A sophisticated control system for the PWM outputs is designed into the
47 ADT747x that allows fan speed to be adjusted automatically based on any of the
48 three temperature sensors. Each PWM output is individually adjustable and
49 programmable. Once configured, the ADT747x will adjust the PWM outputs in
50 response to the measured temperatures without further host intervention.
51 This feature can also be disabled for manual control of the PWM's.
53 Each of the measured inputs (voltage, temperature, fan speed) has
54 corresponding high/low limit values. The ADT747x will signal an ALARM if
55 any measured value exceeds either limit.
57 The ADT747x samples all inputs continuously. The driver will not read
58 the registers more often than once every other second. Further,
59 configuration data is only read once per minute.
61 Chip Differences Summary
62 ------------------------
66 * system acoustics optimizations (not implemented)
77 * 1 Imon input (not implemented)
78 * PECI support (not implemented)
79 * 2 GPIO pins (not implemented)
80 * system acoustics optimizations (not implemented)
85 ADT7490 ADT7476 ADT7475 ADT7473
86 ------- ------- ------- -------
87 in0 2.5VIN (22) 2.5VIN (22) - -
88 in1 VCCP (23) VCCP (23) VCCP (14) VCCP (14)
89 in2 VCC (4) VCC (4) VCC (4) VCC (3)
90 in3 5VIN (20) 5VIN (20)
91 in4 12VIN (21) 12VIN (21)
97 The ADT747x has a 10-bit ADC and can therefore measure temperatures
98 with a resolution of 0.25 degree Celsius. Temperature readings can be
99 configured either for two's complement format or "Offset 64" format,
100 wherein 64 is subtracted from the raw value to get the temperature value.
102 The datasheet is very detailed and describes a procedure for determining
103 an optimal configuration for the automatic PWM control.
108 The driver exposes two trip points per PWM channel.
110 point1: Set the PWM speed at the lower temperature bound
111 point2: Set the PWM speed at the higher temperature bound
113 The ADT747x will scale the PWM linearly between the lower and higher PWM
114 speed when the temperature is between the two temperature boundaries.
115 Temperature boundaries are associated to temperature channels rather than
116 PWM outputs, and a given PWM output can be controlled by several temperature
117 channels. As a result, the ADT747x may compute more than one PWM value
118 for a channel at a given time, in which case the maximum value (fastest
119 fan speed) is applied. PWM values range from 0 (off) to 255 (full speed).
121 Fan speed may be set to maximum when the temperature sensor associated with
122 the PWM control exceeds temp#_max.
124 At Tmin - hysteresis the PWM output can either be off (0% duty cycle) or at the
125 minimum (i.e. auto_point1_pwm). This behaviour can be configured using the
126 pwm[1-*]_stall_disable sysfs attribute. A value of 0 means the fans will shut
127 off. A value of 1 means the fans will run at auto_point1_pwm.
129 The responsiveness of the ADT747x to temperature changes can be configured.
130 This allows smoothing of the fan speed transition. To set the transition time
131 set the value in ms in the temp[1-*]_smoothing sysfs attribute.
136 The nVidia binary driver presents an ADT7473 chip via an on-card i2c bus.
137 Unfortunately, they fail to set the i2c adapter class, so this driver may
138 fail to find the chip until the nvidia driver is patched.