ADT7476 Analog Devices, Inc., ADT7476 Datasheet - Page 48

• Manufacturer Part Number: ADT7476
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7476
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 ADT7476 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
PWM
PWM
Note that the control range for 4-wire fans is much wider than
for 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
MIN
RANGE
RANGE
RANGE
Figure 62. T
MIN
= 30%. The CPU fan is configured to run at
= 10%.
= 80°C for ambient temperature
= 53.33°C for CPU temperature
= 40°C for VRM temperature
= 20%. The rear chassis fan is configured to run at
20
20
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
and % Fan Speed Slopes with PWM
RANGE
RANGE
(A)
(B)
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. B | Page 48 of 72
STEP 7: T
T
temperature channel. Above this temperature, a component
such as the CPU or VRM may be operating beyond its safe
operating limit. When the temperature measured exceeds
T
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.
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
, all fans are driven at 100% PWM duty cycle (full speed)
is the absolute maximum temperature allowed on a
0
0
0
0
THERM
VRM TEMPERATURE
VRM TEMPERATURE
THERM
10
10
minus hysteresis, where hysteresis is the number
RANGE
20
20
FOR TEMPERATURE CHANNELS
and % Fan Speed Slopes for VRM, Ambient, and
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
90
90
100
100