Step 2: Configuring The Mux - Analog Devices ADT7473 Manual

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 Registers 0x5C, 0x5D, and 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.
REMOTE 1 =
AMBIENT TEMP
LOCAL =
VRM TEMP
REMOTE 2 =
CPU TEMP
THERMAL CALIBRATION
100%
0%
T T
MIN RANGE
THERMAL CALIBRATION
100%
0%
T T
MIN RANGE
THERMAL CALIBRATION
100%
0%
T T
MIN RANGE
Figure 47. Assigning Temperature Channels to Fan Channels
Automatic Fan Control Mux Options
<7:5> (BHVR), Registers 0x5c, 0x5d, 0x5e.
000 = Remote 1 temperature controls PWMx
001 = Local temperature controls PWMx
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
channels controls PWMx
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 if the local temperature
exceeds 45°C.
Other Mux Options
<7:5> (BHVR), Registers 0x5c, 0x5d, 0x5e.
011 = PWMx runs full speed
100 = PWMx disabled (default)
111 = manual mode
PWMx is running under software control. In this mode,
PWM duty cycle registers (Registers 0x30 to 0x32) are
writable and control the PWM outputs.
MUX
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
PWM
MIN
RAMP
CONTROL
MUX
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 2
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 3
AND 4
MEASUREMENT
Rev. 0 | Page 35 of 76
PWM
CONFIG
PWM
PWM1
GENERATOR
TACH1
PWM
CPU FAN SINK
CONFIG
PWM
PWM2
GENERATOR
TACH2
PWM
CONFIG
FRONT CHASSIS
PWM
PWM3
GENERATOR
TACH3
REAR CHASSIS
ADT7473