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Step 8 − T
HYST
T
is the amount of extra cooling a fan provides after
HYST
the temperature measured has dropped back below T
before the fan turns off. The premise for temperature
hysteresis (T
HYST
chatter, or cycle on and off regularly, whenever the
temperature hovers around the T
The T
value chosen determines the amount of time
HYST
needed 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
fans from chattering on and off. The T
set at 4°C.
The T
setting applies not only to the temperature
HYST
hysteresis for fan on/off, but the same setting is used for the
REMOTE2 =
CPU TEMP
LOCAL =
VRM TEMP
REMOTE1 =
AMBIENT TEMP
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for Temperature Channels
) is that without it, the fan would merely
setting.
MIN
HYST
default value is
HYST
T
RANGE
100%
0%
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 65. The T
Value Applies to Fan On/Off Hysteresis and THERM Hysteresis
HYST
ADT7476A
T
hysteresis value, described in Step 6 - T
THERM
Temperature
Register 0x6D and Register 0x6E sets the hysteresis for
MIN
both fan on/off and the THERM function.
In some applications, it is required that fans not turn off
below T
MIN
Enhance Acoustics Register 1 (0x62) allow the fans to be
turned off or to be kept spinning below T
always on, the T
temperature drops below T
prevent the
THERM Hysteresis
Any hysteresis programmed via Register 0x6D and
Register 0x6E also applies hysteresis on the appropriate
THERM channel.
PWM
MIN
PWM
CONFIG
PWM
S
GENERATOR
TACHOMETER1
MEASUREMENT
PWM
MIN
PWM
CONFIG
PWM
S
MUX
GENERATOR
TACHOMETER2
MEASUREMENT
PWM
MIN
PWM
CONFIG
PWM
S
GENERATOR
TACHOMETER3
AND 4
MEASUREMENT
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46
Channels.
Therefore,
but remain running at PWM
MIN
MIN
value has no effect on the fan when the
HYST
.
MIN
RAMP
CONTROL
PWM1
(ACOUSTIC
ENHANCEMENT)
TACH1
CPU FAN SINK
RAMP
CONTROL
PWM2
(ACOUSTIC
ENHANCEMENT)
TACH2
RAMP
FRONT CHASSIS
CONTROL
PWM3
(ACOUSTIC
ENHANCEMENT)
TACH3
REAR CHASSIS
for
RANGE
programming
. Bits [7:5] of
. If the fans are
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