adt7476a Analog Devices, Inc., adt7476a Datasheet - Page 46

• Manufacturer Part Number: adt7476a
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7476A
Example: Determining T
Channel
The following example shows how the different T
settings can be applied to three different thermal zones. In this
example, the following T
This example uses the mux configuration described in Step 2—
Configuring the Mux with the ADT7476A connected as shown
in Figure 52. Both CPU temperature and VRM temperature
drive the CPU fan connected to PWM1. Ambient temperature
drives the front chassis fan and rear chassis fan connected to
PWM2 and PWM3. The front chassis fan is configured to
run at PWM
run at PWM
PWM
Note: The control range for 4-wire fans is much wider than that
of 3-wire fans. In many cases, 4-wire fans can start with a PWM
drive of as little as 20% or less. In extreme cases, some 3-wire
fans cannot run unless a PWM drive of 60% or more is applied.
100
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
0
0
0
0
T
T
T
MIN
RANGE
RANGE
RANGE
Figure 62. T
= 10%.
= 80°C for ambient temperature
= 53.33°C for CPU temperature
= 40°C for VRM temperature
20
20
MIN
MIN
= 20%. The rear chassis fan is configured to
= 30%. The CPU fan is configured to run at
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
and % Fan Speed Slopes with PWM
RANGE
(A)
(B)
RANGE
60
60
values apply:
for Each Temperature
80
80
MIN
MIN
100
100
MIN
MIN
120
120
= 20%
and T
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.3°C
16°C
20°C
26.6°C
32°C
40°C
53.3°C
80°C
RANGE
Rev. 0 | Page 46 of 72
STEP 7—T
T
temperature channel. Above this temperature, a component
such as the CPU or VRM can operate beyond its safe operating
limit. When the temperature measured exceeds T
are driven at 100% PWM duty cycle (full speed) to provide
critical system cooling.
The fans remain running at 100% until the temperature drops
below T
programmed into the hysteresis registers (0x6D and 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, and
users should ensure that it is not exceeded under normal system
operating conditions.
THERM
THERM
100
100
Figure 63. T
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
THERM
0
0
is the absolute maximum temperature allowed on a
limit runs all fans at 100%, it has very negative acoustic
0
0
THERM
VRM TEMPERATURE
VRM TEMPERATURE
limit should be considered the maximum worst-case
10
10
THERM
minus hysteresis, where hysteresis is the number
RANGE
20
20
and % Fan Speed Slopes for VRM, Ambient, and
FOR TEMPERATURE CHANNELS
CPU Temperature Channels
TEMPERATURE ABOVE T
AMBIENT TEMPERATURE
TEMPERATURE ABOVE T
30
30
CPU TEMPERATURE
AMBIENT TEMPERATURE
40
40
50
50
CPU TEMPERATURE
60
60
70
MIN
70
MIN
80
80
THERM
90
90
, all fans
100
100