ADT7473_11 ONSEMI [ON Semiconductor], ADT7473_11 Datasheet - Page 40

• Manufacturer Part Number: ADT7473_11
• Description: dbCOOL Remote Thermal Monitor and Fan Control
• Manufacturer: ONSEMI [ON Semiconductor]

Example: Determining T
Channel
T
zones. In this example, the following T
T
T
T
Step 2: Configuring the Mux section, with the ADT7473/
ADT7473−1 connected as shown in Figure 61. Both CPU
temperature and VRM temperature drive the CPU fan
connected to PWM1.
chassis fan connected to PWM2 and PWM3. The front
chassis fan is configured to run at PWM
chassis fan is configured to run at PWM
CPU fan is configured to run at PWM
Note on 4−Wire Fans
for 3−wire fans. In many cases, 4−wire fans can start with a
PWM drive of as little as 20%.
RANGE
RANGE
RANGE
RANGE
100
100
The following example shows how the different T
This example uses the mux configuration described in the
Ambient temperature drives the front chassis fan and rear
The control range for 4−wire fans is much wider than that
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Figure 60. T
0
0
0
0
= 80°C for ambient temperature
= 53.3°C for CPU temperature
= 40°C for VRM temperature
settings can be applied to three different thermal
20
20
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
PWM
and % Fan Speed Slopes with
RANGE
60
60
MIN
= 20%
for Each Temperature
80
80
MIN
MIN
MIN
RANGE
MIN
100
100
MIN
= 10%.
= 20%. The rear
values apply:
= 30%. The
120
120
MIN
http://onsemi.com
25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
and
40
Step 7: T
on a temperature channel. When operating above this
temperature, a component such as the CPU or VRM might
be beyond its safe operating limit. When the temperature
measured exceeds T
PWM duty cycle (full speed) to provide critical system
cooling.
drops below T
number programmed into the hysteresis registers (Register
0x6D and Register 0x6E). The default hysteresis value is 4°C.
worst−case operating temperature of the system. Because
exceeding any T
very negative acoustic effects. Ultimately, this limit should
be set up as a fail−safe, and it should not be exceeded under
normal system operating conditions.
the fan speed no matter how the automatic fan control
settings are configured. This allows some flexibility because
a T
hard limit (such as 70°C), can be programmed as T
Figure 61. T
T
The fans remain running at 100% until the temperature
The T
Note that the T
RANGE
THERM
100
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Ambient, and CPU Temperature Channels
0
0
0
0
THERM
THERM
value can be selected based on its slope, while a
is the absolute maximum temperature allowed
10
10
RANGE
THERM
limit should be considered the maximum
for Temperature Channels
THERM
20
20
THERM
and % Fan Speed Slopes for VRM,
TEMPERATURE ABOVE T
THERM
TEMPERATURE ABOVE T
30
30
− hysteresis, where hysteresis is the
limit runs all fans at 100%, it has
limits are nonmaskable and affect
40
40
all fans are driven at 100%
50
50
60
60
MIN
70
70
MIN
80
80
90
90
MAX
100
100
(the