ADT7473ARQZ-1R7 ON Semiconductor, ADT7473ARQZ-1R7 Datasheet - Page 35

• Manufacturer Part Number: ADT7473ARQZ-1R7
• Description: IC THERM MON FAN CTLR 16-QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7473ARQZ-1R7

• 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

Mux Configuration Example
system using the ADT7473/ADT7473−1 to control three
fans. The CPU fan sink is controlled by PWM1, the front
chassis fan is controlled by PWM2, and the rear chassis fan
is controlled by PWM3. The mux is configured for the
following fan control behaviors:
•
•
Step 3: T
under automatic fan control. The speed at which the fan runs
at T
temperature channel specific, for example, 25°C for
ambient channel, 30°C for VRM temperature, and 40°C for
processor temperature.
64, that can be programmed in 1°C increments. A T
register is associated with each temperature measurement
channel: Remote 1 local and Remote 2 temperature. Once
the T
minimum PWM duty cycle. The fan turns off once the
temperature drops below T
TACH rising edges are counted. See the Fan Startup
Timeout section for more details. In some cases, primarily
for psycho−acoustic reasons, it is desirable that the fan never
switches off below T
Register 1 (0x62), when set, can keep the fans running at the
This is an example of how to configure the mux in a
T
T
To overcome fan inertia, the fan is spun up until two valid
PWM1 (CPU fan sink) is controlled by the fastest speed
calculated by the local (VRM temperature) and
Remote 2 (processor) temperature. In this case, the
CPU fan sink is also used to cool the VRM.
PWM2 (front chassis fan) is controlled by the Remote 1
temperature (ambient).
MIN
MIN
MIN
MIN
is the temperature at which the fans start to turn on
is an 8−bit value, either twos complement or Offset
is programmed later. The T
MIN
value is exceeded, the fan turns on and runs at the
Settings for Thermal Calibration Channels
MIN
. Bits [7:5] of Enhanced Acoustics
MIN
− T
HYST
MIN
.
Figure 51. Mux Configuration Example
values chosen are
http://onsemi.com
MIN
35
•
Example Mux Settings
Bits [7:5] (BHVR), PWM1 Configuration Register (0x5C)
Bits [7:5] (BHVR), PWM2 Configuration Register (0x5D)
Bits [7:5] (BHVR), PWM3 Configuration Register (0x5E)
PWM minimum duty cycle, if the temperature falls below
T
T
Register 0x67, Remote 1 Temperature T
Register 0x68, Local Temperature T
Register 0x69, Remote 2 Temperature T
Enhanced Acoustics Register 1 (0x62)
Bit 7 (MIN3) = 0, PWM3 is off (0% PWM duty cycle) when
temperature is below T
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum duty
cycle below T
Bit 6 (MIN2) = 0, PWM2 is off (0% PWM duty cycle) when
temperature is below T
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minimum duty
cycle below T
Bit 5 (MIN1) = 0, PWM1 is off (0% PWM duty cycle) when
temperature is below T
Bit 5 (MIN1) = 1, PWM1 runs at PWM1 minimum duty
cycle below T
MIN
MIN
These settings configure the mux, as shown in Figure 51.
PWM3 (rear chassis fan) is controlled by the Remote 1
temperature (ambient).
101 = Fastest speed calculated by local and Remote 2
000 = Remote 1 temperature controls PWM2
000 = Remote 1 temperature controls PWM3
Registers
.
temperature controls PWM1
MIN
MIN
MIN
− T
− T
− T
HYST
HYST
HYST
MIN
MIN
MIN
.
.
.
− T
− T
− T
HYST
HYST
HYST
.
.
.
MIN
MIN
MIN
= 0x9A (90°C)
= 0x9A (90°C)
= 0x9A (90°C)