W83792G Nuvoton Technology Corporation of America, W83792G Datasheet - Page 29

• Manufacturer Part Number: W83792G
• Description: IC MONITOR H/W 48-LQFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83792G

• Function: Hardware Monitor
• Topology: ADC, Fan Control, Register Bank
• Sensor Type: External
• Sensing Temperature: External Sensor
• Output Type: I²C™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Must be take care when choosing the OP-AMP and the transistor. The OP-AMP is used for amplify the
5V range of the DC output up to 12V. The transistor should has a suitable
current pulling down the OP-AMP ’s output and gain the common current to operate the fan at fully
speed. (For more cost and effort efficiently solution please refer to W8339TS/QS –which is the DC fan
pre-driver and it could provide up to 24V gate voltage for external N-channel MOSFET with lower cost
and better performance)
7.7.3
W83792D/G supports two Smart Fan function and mapping to temp1 (FAN1, PWMOUT1), temp2
(FAN2, PWMOUT2), temp3 ( FAN3, PWMOUT3) .Smart Fan Control provides two mechanisms. One
is Thermal Cruise mode and the other is Smart Fan
7.7.3.1. Thermal Cruise mode
At this mode, W83792D/G provides the Smart Fan system to automatically control fan speed to keep
the temperatures of CPU and the system within specific range. At first a wanted temperature and
interval must be set (ex. 55 °C ± 3 °C) by BIOS and the fan speed will be lowered as long as the
current temperature remains below the setting value. Once the temperature exceeds the high limit
(58°C), the fan will be turned on with a specific speed set by BIOS (ex: 80% duty cycle) and
automatically controlled its PWM duty cycle with the temperature varying. Three conditions may occur:
(1) If the temperature still exceeds the high limit (ex: 58°C), PWM duty cycle will increase slowly. If the
(2) If the temperature goes below the high limit (ex: 58°C), but still above the low limit (ex: 52°C), the
(3) If the temperature goes below the low limit (ex: 52°C), PWM duty cycle will decrease slowly to 0 or
Figure 7-1, 7-2 gives an illustration of Thermal Cruise Mode.
fan has been operating in its full speed but the temperature still exceeds the high limit (ex: 58°C),
a warning message will be issued to protect the system.
fan speed will be fixed at the current speed because the temperature is in the target range (ex: 52
°C ~ 58°C).
a preset stop value until the temperature exceeds the low limit.
Smart FanTM I Control
PWM
Duty
Cycle
58`C
55`C
52`C
100
50
0
Fan Start = 20%
A
B
Figure 7-1.
- 23 -
TM
C
II mode.
D
Publication Release Date: April 26, 2006
W83792AD/AG/D/G
β
value to avoid its base
Revision 0.9