ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 42

• Manufacturer Part Number: ADT7475
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7475
As T
gets smaller, the fans reach 100% speed with a smaller
temperature change.
Selecting T
The T
Remote 1, local, and Remote 2 temperatures. Bits [7:4]
(RANGE) of Register 0x5F to Register 0x61 define the T
value for each temperature channel.
RANGE
RANGE
Figure 56. Changing PWM
100%
100%
PWM
is changed, the slope also changes. As T
10%
MAX
10%
0%
Figure 55. Increasing T
0%
value can be selected for each temperature channel:
RANGE
T
MIN – HYST
T
MIN – HYST
T
MIN
MAX
RANGE
T
30°C
RANGE
Does Not Change the AFC Slope
40°C
45°C
Changes the AFC Slope
54°C
RANGE
RANGE
Rev. B | Page 42 of 68
Table 14. Selecting a T
Bits [7:4]
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
1
Actual Changes in PWM Output (Advanced
Acoustics Settings)
While the automatic fan control algorithm describes the general
response of the PWM output, the enhanced acoustics registers
(0x62 and 0x63) can be used to set/clamp the maximum rate of
change of PWM output for a given temperature zone. This means
if T
change in temperature can cause a large change in PWM output
and an audible change in fan speed, which may be noticeable/
annoying to users. Decreasing the PWM output’s maximum rate
of change, by programming the smoothing on the appropriate
temperature channels (Register 0x62 and Register 0x63), clamps
the fan speed’s maximum rate of change in the event of a
temperature spike. The PWM duty cycle increases slowly until
the PWM duty cycle reaches the appropriate duty cycle as defined
by the AFC curve.
Figure 57 shows PWM duty cycle versus temperature for each
T
affects fan speed vs. temperature. As can be seen from the
graph, the effect on fan speed is nonlinear.
Register 0x5F configures Remote 1 T
T
RANGE
RANGE
RANGE
; Register 0x61 configures Remote 2 T
setting. The lower graph shows how each T
is programmed with a steep AFC slope, a relatively small
1
RANGE
Value
RANGE
T
2
2.5
3.33
4
5
6.67
8
10
13.33
16
20
26.67
32 (default)
40
53.33
80
; Register 0x60 configures local
RANGE
RANGE
(°C)
.
RANGE
setting