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100%
0%
REMOTE 2 =
CPU TEMP
LOCAL =
VRM TEMP
REMOTE 1 =
AMBIENT TEMP
STEP 8: T
FOR TEMPERATURE CHANNELS
HYST
T
is the amount of extra cooling a fan provides after the
HYST
temperature measured has dropped back below T
fan turns off. The premise for temperature hysteresis (T
that, without it, the fan would merely chatter or cycle on and off
regularly whenever temperature is hovering at about the T
setting.
The T
value chosen determines the amount of time needed
HYST
for the system to cool down or heat up as the fan is turning on
and off. Values of hysteresis are programmable in the range 1°C
to 15°C. Larger values of T
HYST
on and off. The T
default value is set at 4°C.
HYST
The T
setting applies not only to the temperature hysteresis
HYST
for fan on/off, but the same setting is used for the T
hysteresis value, described in Step 6: T
Channels. Therefore, programming Registers 0x6D and 0x6E
sets the hysteresis for both fan on/off and the THERM function.
T
RANGE
T
T
MIN
THERM
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 59. How T
before the
MIN
HYST
prevent the fans from chattering
THERM
for Temperature
RANGE
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
Relates to Automatic Fan Control
THERM
Hysteresis Registers
Reg. 0x6D, Remote 1, Local Hysteresis Register
<7:4>, Remote 1 temperature hysteresis (4°C default).
) is
<3:0>, Local temperature hysteresis (4°C default).
MIN
Reg. 0x6E, Remote 2 Temp Hysteresis Register
<7:4>, Remote 2 temperature hysteresis (4°C default).
In some applications, it is required that fans not turn off below
T
, but remain running at PWM
MIN
Acoustics Register 1 (Reg. 0x62) allow the fans to be turned off
or to be kept spinning below T
T
value has no effect on the fan when the temperature drops
HYST
below T
.
MIN
Rev. 0 | Page 43 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
. Bits <7:5> of Enhanced
MIN
. If the fans are always on, the
MIN
ADT7473
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