ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 39

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

STEP 3: T
CALIBRATION CHANNELS
T
automatic fan control. The speed at which the fan runs at T
programmed later in the process. The T
temperature channel specific, for example, 25°C for ambient
channel, 30°C for VRM temperature, and 40°C for processor
temperature.
T
that can be programmed in 1°C increments. There is a
T
ment channel: Remote 1, local, and Remote 2 temperatures.
Once the T
the minimum PWM duty cycle. The fan turns off once the
temperature has dropped below T
To overcome fan inertia, the fan is spun up until two valid
TACH rising edges are counted. See the Fan Start-Up Timeout
section for more details. In some cases, primarily for psycho-
acoustic reasons, it is desirable that the fan never switch off
below T
when set, keep the fans running at the PWM minimum duty
cycle, if the temperature should fall below T
MIN
MIN
MIN
is the temperature at which the fans turn on under
is an 8-bit value, either twos complement or Offset 64,
register associated with each temperature measure-
MIN
. Bits [7:5] of Enhanced Acoustics Register 1 (0x62),
MIN
MIN
value is exceeded, the fan turns on and runs at
SETTINGS FOR THERMAL
AMBIENT TEMP
REMOTE 2 =
REMOTE 1 =
VRM TEMP
CPU TEMP
LOCAL =
100%
0%
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
MIN
T
T
T
T
MIN
MIN
MIN
MIN
− T
MIN
HYST
values chosen are
MIN
.
T
T
T
.
RANGE
RANGE
RANGE
Figure 49. Understanding the T
100%
100%
100%
0%
0%
0%
MUX
MIN
Rev. B | Page 39 of 68
is
PWM
PWM
PWM
MIN
MIN
MIN
CONFIG
CONFIG
CONFIG
T
Register 0x67, Remote 1 Temperature T
Register 0x68, Local Temperature T
Register 0x69, Remote 2 Temperature T
Enhanced Acoustics Register 1 (0x62)
Bit 7 (MIN3) = 0, PWM3 is off (0% PWM duty cycle) when
temperature is below T
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum duty cycle
below T
Bit 6 (MIN2) = 0, PWM2 is off (0% PWM duty cycle) when
temperature is below T
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minimum duty cycle
below T
Bit 5 (MIN1) = 0, PWM1 is off (0% PWM duty cycle) when
temperature is below T
Bit 5 (MIN1) = 1, PWM1 runs at PWM1 minimum duty cycle
below T
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
PWM
PWM
PWM
MIN
GENERATOR
GENERATOR
GENERATOR
MIN
AND 4
Registers
PWM
PWM
PWM
Parameter
MIN
MIN
MIN
− T
− T
− T
HYST
HYST
HYST
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
.
.
.
RAMP
RAMP
RAMP
MIN
MIN
MIN
− T
− T
− T
HYST
HYST
HYST
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
.
.
.
MIN
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
= 0x5A (90°C)
MIN
MIN
= 0x5A (90°C)
= 0x5A (90°C)
ADT7475