Step 3: Tmin Settings For Thermal Calibration Channels - Analog Devices ADT7473 Manual

STEP 3: T SETTINGS FOR THERMAL
MIN
CALIBRATION CHANNELS
T is the temperature at which the fans start to turn on under
MIN
automatic fan control. The speed at which the fan runs at T
programmed later. The T
MIN
channel specific, for example, 25°C for ambient channel, 30°C
for VRM temperature, and 40°C for processor temperature.
T is an 8-bit value, either twos complement or Offset 64, that
MIN
can be programmed in 1°C increments. A T
associated with each temperature measurement channel:
Remote 1 local, and Remote 2 temperature. Once the T
is exceeded, the fan turns on and runs at the minimum PWM
duty cycle. The fan turns off once the temperature drops below
T − T .
MIN HYST
To overcome fan inertia, the fan is spun up until two valid
TACH rising edges are counted. See the Fan Startup Timeout
section for more details. In some cases, primarily for psycho-
acoustic reasons, it is desirable that the fan never switches off
below T . Bits <7:5> of Enhanced Acoustics Register 1
MIN
(Reg. 0x62), when set, keep the fans running at the PWM
minimum duty cycle, if the temperature falls below T
100%
0%
REMOTE 2 =
CPU TEMP
LOCAL =
VRM TEMP
REMOTE 1 =
AMBIENT TEMP
values chosen are temperature
register is
MIN
MIN
.
MIN
T
MIN
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 49. Understanding the T
T Registers
MIN
Reg. 0x67, Remote 1 Temperature T
Reg. 0x68, Local Temperature T
is
MIN
Reg. 0x69, Remote 2 Temperature T
Enhance Acoustics Register 1 (Reg. 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 – T
value
MIN
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 – T
MIN
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 – T
MIN
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
Parameter
MIN
Rev. 0 | Page 37 of 76
= 0x9A (90°C)
MIN
= 0x9A (90°C)
MIN
= 0x9A (90°C)
MIN
– T .
MIN HYST
.
HYST
– T .
MIN HYST
.
HYST
– T .
MIN HYST
.
HYST
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
ADT7473