ADT7475ARQZ ON Semiconductor, ADT7475ARQZ Datasheet - Page 36

• Manufacturer Part Number: ADT7475ARQZ
• Description: IC REMOTE THERMAL CTRLR 16-QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7475ARQZ

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Actual Changes in PWM Output (Advanced
Acoustics Settings)
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
with a steep AFC slope, a relatively small 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.
each T
T
seen from the graph, the effect on fan speed is non−linear.
100
RANGE
100
While the automatic fan control algorithm describes the
Figure 56 shows PWM duty cycle versus temperature for
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Figure 56. T
0
0
0
0
RANGE
setting affects fan speed vs. temperature. As can be
20
20
setting. The lower graph shows how each
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
vs. Actual Fan Speed (not PWM
Drive) Profile
(B)
(A)
60
60
80
80
MIN
MIN
RANGE
100
100
is programmed
120
120
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25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
36
PWM duty cycle. Clearly, the minimum PWM duty cycle,
PWM
actually performs in the system. Figure 57 shows how
T
It can be seen that the fan actually runs at about 45% fan
speed when the temperature exceeds T
Example: Determining T
Channel
T
zones. In this example, the following T
Step 2: Configuring the Mux, with the ADT7475 connected
as shown in Figure 47. Both CPU temperature and VRM
temperature drive the CPU fan connected to PWM1.
RANGE
RANGE
100
100
The graphs in Figure 56 assume that the fan starts from 0%
The following example shows how the different T
This example uses the mux configuration described in
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Figure 57. T
0
0
0
0
T
T
T
MIN
RANGE
RANGE
RANGE
is affected when the PWM
settings can be applied to three different thermal
, needs to be factored in to see how the loop
20
20
= 80°C for ambient temperature
= 53.33°C for CPU temperature
= 40°C for VRM temperature
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
PWM
and % Fan Speed Slopes with
RANGE
(A)
(B)
60
60
MIN
= 20%
for Each Temperature
80
80
MIN
MIN
MIN
RANGE
MIN
value is set to 20%.
100
100
.
values apply:
120
120
MIN
25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
25C
2.55C
3.335C
45C
55C
6.675C
85C
105C
13.35C
165C
205C
26.65C
325C
405C
53.35C
805C
and