Analog Devices ADT7473 Manual page 36

ADT7473
Mux Configuration Example
This is an example of how to configure the mux in a system
using the ADT7473 to control three fans. The CPU fan sink is
controlled by PWM1, the front chassis fan is controlled by
PWM 2, and the rear chassis fan is controlled by PWM3. The
mux is configured for the following fan control behavior:
•
PWM1 (CPU fan sink) is controlled by the fastest speed
calculated by the local (VRM temperature) and Remote 2
(processor) temperature. In this case, the CPU fan sink is
also being used to cool the VRM.
•
PWM2 (front chassis fan) is controlled by the Remote 1
temperature (ambient).
•
PWM3 (rear chassis fan) is controlled by the Remote 1
temperature (ambient).
REMOTE 2 =
CPU TEMP
LOCAL =
VRM TEMP
REMOTE 1 =
AMBIENT 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 48. Mux Configuration Example
Example Mux Settings
<7:5> (BHVR), PWM1 Configuration Register 0x5c.
101 = Fastest speed calculated by local and Remote 2
temperature controls PWM1
<7:5> (BHVR), PWM2 Configuration Register 0x5d.
000 = Remote 1 temperature controls PWM2
<7:5> (BHVR), PWM3 Configuration Register 0x5e.
000 = Remote 1 temperature controls PWM3
These settings configure the mux, as shown in Figure 48.
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 1
MUX
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 2
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 3
AND 4
MEASUREMENT
Rev. 0 | Page 36 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