ADT7476ARQZ ON Semiconductor, ADT7476ARQZ Datasheet - Page 42

• 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

Example: Determining T
Channel
T
zones. In this example, the following T
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
chassis fan is configured to run at PWM
CPU fan is configured to run at PWM
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.
RANGE
100
100
The following example shows how the different T
This example uses the mux configuration described in
Note: The control range for 4−wire fans is much wider
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Figure 62. T
0
0
0
0
T
T
T
RANGE
RANGE
RANGE
settings can be applied to three different thermal
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
100
100
MIN
= 10%.
= 20%. The rear
values apply:
= 30%. The
120
120
MIN
http://onsemi.com
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
42
Step 7—T
on a 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
cycle (full speed) to provide critical system cooling.
drops below T
the number programmed into the hysteresis registers (0x6D
and 0x6E). The default hysteresis value is 4°C.
worst−case operating temperature of the system. Because
exceeding any T
very negative acoustic 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.
speed no matter how automatic fan control settings are
configured. This allows some flexibility, because a T
value can be selected based on its slope, while a hard limit
(such as 70°C), can be programmed as T
Figure 63. T
T
The fans remain running at 100% until the temperature
The T
Note: T
THERM
100
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
Ambient, and CPU Temperature Channels
0
0
0
0
THERM
VRM TEMPERATURE
VRM TEMPERATURE
THERM
THERM
THERM
is the absolute maximum temperature allowed
10
10
RANGE
THERM
limit should be considered the maximum
THERM
20
20
, all fans are driven at 100% PWM duty
for Temperature Channels
limits are nonmaskable and affect the fan
and % Fan Speed Slopes for VRM,
TEMPERATURE ABOVE T
AMBIENT TEMPERATURE
TEMPERATURE ABOVE T
30
30
minus hysteresis, where hysteresis is
CPU TEMPERATURE
limit runs all fans at 100%, it has
AMBIENT TEMPERATURE
40
40
50
50
CPU TEMPERATURE
60
60
70
MIN
70
MIN
80
80
MAX
90
90
RANGE
100
100
(the