ADT7476ARQZ ON Semiconductor, ADT7476ARQZ Datasheet - Page 41

• Manufacturer Part Number: ADT7476ARQZ
• Description: IC REMOTE THERMAL CTRLR 24QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7476ARQZ

• 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: 24-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

Selecting T
channel: Remote 1, local, and Remote 2 temperature. Bits
[7:4] (T
T
Actual Changes in PWM Output
(Advanced Acoustics Settings)
general response of the PWM output, it is also necessary to
note that the enhance 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 that
if T
steep, a relatively small change in temperature could cause
a large change in PWM output and possibly an audible
change in fan speed, which can be noticeable/ bothersome
to end users.
programming the smoothing on the appropriate temperature
channels (Register 0x62 and Register 0x63) changes how
fast the fan speed increases/decreases 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.
Table 13. Selecting a T
RANGE
1. Register 0x5F configures Remote 1 T
The T
While the automatic fan control algorithm describes the
Decreasing the speed the PWM output changes by
RANGE
configures local T
T
Bits [7:4] (Note 1)
RANGE
RANGE
RANGE
value for each temperature channel.
is programmed with an AFC slope that is quite
0000
0001
0010
0100
0101
1000
1001
1010
.
0011
0110
0111
1011
1100
1101
1110
RANGE
1111
) of Register 0x5F to Register 0x61 define the
value can be selected for each temperature
RANGE
RANGE
; Register 0x61 configures Remote 2
Value
T
RANGE
32 (default)
RANGE
13.33
26.67
53.33
3.33
6.67
2.5
10
16
20
40
80
2
4
5
8
; Register 0x60
(5C)
http://onsemi.com
41
T
setting affects fan speed vs. temperature. As can be seen
from the graph, the effect on fan speed is nonlinear.
PWM duty cycle. Clearly, the minimum PWM duty cycle,
PWM
actually performs in the system. Figure 62 shows how
T
It can be seen that the fan actually runs at about 45% fan
speed when the temperature exceeds T
RANGE
RANGE
100
Figure 61 shows PWM duty cycle vs. temperature for each
100
The graphs in Figure 61 assume that the fan starts from 0%
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
0
0
0
0
MIN
Figure 61. T
setting. The lower graph shows how each T
is affected when the PWM
, needs to be factored in to see how the loop
20
20
(Not PWM Drive) Profile
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
40
40
RANGE
(B)
(A)
60
60
vs. Actual Fan Speed
80
80
MIN
MIN
MIN
MIN
value is set to 20%.
100
100
.
120
120
RANGE
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