ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 44

• Manufacturer Part Number: ADT7473
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7473
Note on 4-Wire Fans
The control range for 4-wire fans is much wider than that of
3
drive of as little as 20%.
STEP 7: T
T
temperature channel. When operating above this temperature, a
component such as the CPU or VRM might be beyond its safe
operating limit. When the temperature measured exceeds
T
to provide critical system cooling.
-wire fans. In many cases, 4-wire fans can start with a PWM
THERM
THERM
100
100
Figure 58. T
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
, all fans are driven at 100% PWM duty cycle (full speed)
is the absolute maximum temperature allowed on a
0
0
0
0
THERM
10
10
RANGE
20
20
FOR TEMPERATURE CHANNELS
and % Fan Speed Slopes for VRM, Ambient, and
CPU Temperature Channels
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
30
30
40
40
50
50
60
60
70
MIN
70
MIN
80
80
90
90
100
100
Rev. A | Page 44 of 76
The fans remain running at 100% until the temperature drops
below T
programmed into the hysteresis registers (Register 0x6D and
Register 0x6E). The default hysteresis value is 4°C.
The T
operating temperature of the system. Because exceeding any
T
effects. Ultimately, this limit should be set up as a fail-safe, an
one should ensure it is not exceeded
operating conditions.
Note that the T
speed no matter how the automatic fan control settings are
configured. This allows some flexibility because a T
can be selected based on its slope, while a hard limit (such as
70°C), can be programmed as T
the fan reaches full speed) by setting T
example, 70°C).
THERM Registers
Register 0x6A, Remote 1 THERM Temperature Limit = 0xA4
(100°C default)
Register 0x6B, Local THERM Temperature Limit = 0xA4
(100°C default)
Register 0x6C, Remote 2 THERM Temperature Limit = 0xA4
(100°C default)
Hysteresis Registers
Register 0x6D, Remote 1 Local Temperature Hysteresis Register
Bits [7:4] Remote 1 temperature hysteresis (4°C default)
Bits [3:0] Local temperature hysteresis (4°C default)
Register 0x6E, Remote 2 Temperature Hysteresis Register
Bits [7:4] Remote 2 temperature hysteresis (4°C default)
Because each hysteresis setting is four bits, hysteresis values are
programmable from 1°C to 15°C. It is not recommended that
hysteresis values be programmed to 0°C, because this disables
hysteresis. In effect, this would cause the fans to cycle between
normal speed and 100% speed, creating unsettling acoustic
noise.
THERM
THERM
limit runs all fans at 100%, it has very negative acoustic
THERM
limit should be considered the maximum worst-case
− hysteresis, where hysteresis is the number
THERM
limits are nonmaskable and affect the fan
MAX
(the temperature at which
under normal system
THERM
to that limit (for
RANGE
value
d