ADT7467
100
90
80
70
60
50
40
30
20
10
0
0
20
40 60 80 100
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
100
90
80
70
60
50
40
30
20
10
0
0
10
20 30 40
50 60 70 80
90 100
TEMPERATURE ABOVE T MIN
TEMPERATURE ABOVE T MIN
100
90
80
70
60
50
40
30
20
10
0
0
20
40 60 80 100
TEMPERATURE ABOVE T MIN
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
100
90
80
70
60
50
40
30
20
10
0
0
10
20 30 40 50 60 70 80
TEMPERATURE ABOVE T MIN
90 100
Figure 64. T RANGE and Percentage of Fan Speed
Slopes with PWM MIN = 20%
Determining T RANGE for Each Temperature Channel
The following example shows how different T MIN and
T RANGE settings can be applied to three thermal zones. In
this example, the following T RANGE values apply:
T RANGE = 80 ? C for ambient temperature
T RANGE = 53.3 ? C for CPU temperature
T RANGE = 40 ? C for VRM temperature
This example uses the mux configuration described in the
Step 2: Configuring the Mux section, with the ADT7467
connected as shown in Figure 55. Both CPU temperature
and VRM temperature drive the CPU fan connected to
PWM1. Ambient temperature drives the front chassis fan
and the rear chassis fan connected to PWM2 and PWM3.
The front chassis fan is configured to run at
PWM MIN = 20%; the rear chassis fan is configured to run at
PWM MIN = 30%. The CPU fan is configured to run at
PWM MIN = 10%.
4-wire Fans
The control range for 4-wire fans is much wider than that
of 2-wire or 3-wire fans. In many cases, 4-wire fans can start
with a PWM drive of as little as 20%.
Figure 65. T RANGE and Percentage of Fan Speed
Slopes for VRM, Ambient, and CPU Temperature
Channels
STEP 7: T THERM for Temperature Channels
T THERM is the absolute maximum temperature allowed
on a temperature channel. Above this temperature, a
component such as the CPU or VRM might be operating
beyond its safe operating limit. When the temperature
measured exceeds T THERM , all fans are driven at 100%
PWM duty cycle (full speed) to provide critical system
cooling.
The fans remain running at 100% until the temperature
drops below T THERM minus hysteresis, where hysteresis is
the number programmed into the Hysteresis Registers 0x6D
and 0x6E. The default hysteresis value is 4 ? C.
The T THERM limit should be considered the maximum
worst-case operating temperature of the system. Because
exceeding any T THERM limit runs all fans at 100%, it has
significant negative acoustic effects. Ultimately, this limit
should be set up as a fail-safe, and users should ensure that
it is not exceeded under normal system operating conditions.
Note that the T THERM limits are nonmaskable and affect
the fan speed regardless of the configuration of the
automatic fan control settings. This allows some flexibility,
because a T RANGE value can be selected based on its slope,
http://onsemi.com
41
相关PDF资料
ADT7468ZEVB BOARD EVAL FOR ADT7468
ADT7473ZEVB BOARD EVALUATION FOR ADT7473
ADT7475EBZEVB BOARD EVALUATION FOR ADT7475
ADT7476EBZEVB BOARD EVALUATION FOR ADT7476
ADT7490ZEVB BOARD EVALUATION FOR ADT7490
ADZS-21262-1-EZEXT BOARD DAUGHTER FOR ADSP-21262
ADZS-BF-EZEXT-1 BOARD DAUGHTER ADSP-BF533/561KIT
ADZS-BFAV-EZEXT BOARD DAUGHT ADSP-BF533,37,61KIT
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