ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 37

• Manufacturer Part Number: ADT7475
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

STEP 2: CONFIGURING THE MUX
After the system hardware configuration is determined,
the fans can be assigned to particular temperature channels.
Not only can fans be assigned to individual channels but the
behavior of the fans is also configurable. For example, fans can
be run under automatic fan control, manually under software
control, or at the fastest speed calculated by multiple
temperature channels. The mux is the bridge between
temperature measurement channels and the three PWM
outputs.
Bits [7:5] (BHVR) of Register 0x5C, Register 0x5D, and Register
0x5E (PWM configuration registers) control the behavior of the
fans connected to the PWM1, PWM2, and PWM3 outputs.
The values selected for these bits determine how the mux
connects a temperature measurement channel to a PWM
output.
Automatic Fan Control Mux Options
Bits [7:5] (BHVR), Register 0x5C, Register 0x5D, and Register
0x5E.
000 = Remote 1 temperature controls PWMx
001 = local temperature controls PWMx
AMBIENT TEMP
REMOTE 1 =
REMOTE 2 =
VRM TEMP
CPU TEMP
LOCAL =
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
MIN
MIN
MIN
Figure 47. Assigning Temperature Channels to Fan Channels
T
T
T
RANGE
RANGE
RANGE
100%
100%
100%
0%
0%
0%
MUX
Rev. B | Page 37 of 68
MUX
PWM
PWM
PWM
MIN
MIN
MIN
CONFIG
CONFIG
CONFIG
The fastest speed calculated options pertain to controlling
one PWM output based on multiple temperature channels.
The thermal characteristics of the three temperature zones
can be set to drive a single fan. An example is the fan turning
on when Remote 1 temperature exceeds 60°C or when the local
temperature exceeds 45°C.
Other Mux Options
Bits [7:5] (BHVR), Register 0x5C, Register 0x5D, and Register
0x5E.
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
PWM
PWM
PWM
010 = Remote 2 temperature controls PWMx
101 = Fastest speed calculated by local and Remote 2
temperature controls PWMx
110 = Fastest speed calculated by all three temperature
channel controls PWMx
011 = PWMx runs full speed.
100 = PWMx disabled (default).
111 = manual mode. PWMx is running under software
control. In this mode, PWM current duty cycle registers
(0x30 to 0x32) are writable and control the PWM outputs.
GENERATOR
GENERATOR
GENERATOR
AND 4
PWM
PWM
PWM
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
ADT7475