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

ADT7473
STEP 3: T SETTINGS FOR THERMAL
MIN
CALIBRATION CHANNELS
T is the temperature at which the fans start to turn on und
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
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 Enhance Acoustics Register 1
MIN
(0x62), when set, can keep the fans running at the PWM
minimum duty cycle, if the temperature falls below T
values chosen are temperature
Offset 64, that
register is
MIN
MIN
.
MIN
T Registers
MIN
Register 0x67, Remote 1 Temperature T
er
Register 0x68, Local Temperature T
is
MI N
Register 0x69, Remote 2 Temperature
Enhance Acoustics Register 1 (0x62)
Bit 7 (MIN3) = 0, PWM3 is of
temp erature is below T
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum d
belo w T − T
value
MIN
Bit 6 (MIN2) = 0, PWM2 is o
temperature is below T
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minim
belo w T − T
MIN
Bit 5 (MIN1) = 0, PW
temperature is below T
Bit 5 (MIN1) =
below T − T
MIN
Rev. A | Page 38 of 76
= 0x9A (90°C
MIN
= 0x9A (90°C)
MIN
T = 0x9A (90°C)
MIN
f (0% PWM duty cycle) when
− T .
MIN HY ST
.
HYST
ff (0% PWM duty cycle) when
− T .
MIN HYST
.
HYST
M1 is off (0% PWM duty cycle) when
− T .
MIN HYST
1, PWM1 runs at PWM1 minimum duty cycle
.
HYST
)
uty cycle
um duty cycle