Analog Devices ADT7473 Manual page 41

100
90
80
70
60
50
40
30
20
10
0
0 20 40
TEMPERATURE ABOVE T
100
90
80
70
60
50
40
30
20
10
0
0 20 40
TEMPERATURE ABOVE T
Figure 61. T vs. Actual Fan Speed Profile
RANGE
Example: Determining T
RANGE
Channel
The following example shows how the different T
settings can be applied to three different thermal zones. In this
example, the following T
RANGE
T = 80°C for ambient temperature
RANGE
T = 53.3°C for CPU temperature
RANGE
T = 40°C for VRM temperature
RANGE
This example uses the mux configuration described in the
Step 2: Configuring the Mux section, with the ADT7473/
ADT7473-1 connected as shown in Figure 63. Both CPU
temperature and VRM temperature drive the CPU fan
connected to PWM1.
Ambient temperature drives the front chassis fan and rear
chassis fan connected to PWM2 and PWM3. The front chassis
fan is configured to run at PWM
is configured to run at PWM
configured to run at PWM
MIN
Note on 4-Wire Fans
The control range for 4-wire fans is much wider than that for
3-wire fans. In many cases, 4-wire fans can start with a PWM
drive of as little as 20%.
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
60 80 100 120
MIN
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
60 80 100 120
MIN
for Each Temperature
and T
MIN
values apply:
= 20%. The rear chassis fan
MIN
= 30%. The CPU fan is
MIN
= 10%.
100
90
80
70
60
50
40
30
20
10
0
0
100
90
80
70
60
50
40
30
20
10
0
0
Figure 62. T
100
90
80
RANGE
70
60
50
40
30
20
10
0
0
100
90
80
70
60
50
40
30
20
10
0
0
Figure 63. T
Rev. C | Page 41 of 72
ADT7473/ADT7473-1
20 40 60 80 100
TEMPERATURE ABOVE T
MIN
20 40 60 80 100
TEMPERATURE ABOVE T
MIN
and % Fan Speed Slopes with PWM
RANGE
10 20 30 40 50 60 70
TEMPERATURE ABOVE T
MIN
10 20 30 40 50 60 70
TEMPERATURE ABOVE T
MIN
and % Fan Speed Slopes for VRM, Ambient, and
RANGE
CPU Temperature Channels
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
120
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
120
= 20%
MIN
80 90 100
80 90 100