ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 45

• Manufacturer Part Number: ADT7475
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

STEP 8: T
T
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 the temperature is hovering at about the
T
The T
for the system to cool down or heat up as the fan turns on and
off. Values of hysteresis are programmable in the range 1°C to
15°C. Larger values of T
and off. The T
The T
for fan on/off, but the same setting is used for the T
hysteresis value, described in Step 6: T
Channels. Therefore, programming Register 0x6D and Register
0x6E sets the hysteresis for both fan on/off and the THERM
function.
HYST
MIN
setting.
is the amount of extra cooling a fan provides after the
HYST
HYST
value chosen determines the amount of time needed
setting applies not only to the temperature hysteresis
HYST
HYST
FOR TEMPERATURE CHANNELS
AMBIENT TEMP
default value is set at 4°C.
REMOTE 2 =
REMOTE 1 =
VRM TEMP
CPU TEMP
LOCAL =
HYST
100%
0%
prevent the fans from chattering on
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
T
MIN
MIN
MIN
MIN
RANGE
T
for Temperature
RANGE
T
T
T
RANGE
RANGE
RANGE
Figure 60. How T
T
100%
100%
100%
MIN
THERM
0%
0%
0%
THERM
before the
HYST
MUX
) is
THERM
Rev. B | Page 45 of 68
Relates to Automatic Fan Control
PWM
PWM
PWM
MIN
MIN
MIN
In some applications, it is required that fans not turn off below
T
Acoustics Register 1 (0x62) allow the fans to be turned off or to
be kept spinning below T
value has no effect on the fan when the temperature drops
below T
THERM Hysteresis
Any hysteresis programmed via Register 0x6D and Register
0x6E also applies to hysteresis on the appropriate THERM
channel.
CONFIG
CONFIG
CONFIG
MIN
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
but remain running at PWM
AND 4
PWM
PWM
PWM
MIN
.
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
MIN
. If the fans are always on, the T
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
MIN
. Bits [7:5] of Enhanced
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
ADT7475
HYST