W83791G Nuvoton Technology Corporation of America, W83791G Datasheet - Page 31

• Manufacturer Part Number: W83791G
• Description: IC MONITOR H/W 48-LQFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83791G

• Function: Hardware Monitor
• Topology: ADC
• 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

6.8.1
The W83791D/G can connect three thermistors to measure three different environmental
temperatures. The specification of thermistor should be considered to (1) β value is 3435K, (2) resistor
value is 10K ohms at 25°C. In the Figure 11, the themistor is connected by a serial resistor with 10K
Ohms (1% error), then connect to VREF (Pin 37).
6.8.2
The W83791D/G can alternate the thermistor to Pentium II/III
2N3904 and the circuit connection is shown as Figure 11. The pin of Pentium II/III
power supply ground (GND) and the pin D+ is connected to pin PIITDx in the W83791D/G. The
resistor R=30K ohms should be connected to VREF to supply the diode bias current and the bypass
capacitor C=3300pF should be added to filter the high frequency noise. The transistor 2N3904 should
be connected to a form with a diode, that is, the Base (B) and Collector (C) in the 2N3904 should be
tied together to act as a thermal diode.
6.8.3
SMI# interrupt for voltage is Two-Times Interrupt Mode. Voltage exceeding high limit or going below
low limit will causes an interrupt if the previous interrupt has been reset by reading all the interrupt
Status Register. (Figure 12-1)
Monitor temperature from thermistor:
Monitor temperature from Pentium IITM thermal diode or bipolar transistor 2N3904
SMI# interrupt for W83791D Voltage
P e ntium II/III
T emperature S ensor
T h erminal
Bipolar T ransisto r
C P U
B
D iode
O R
C
E
2N 39 04
D +
D -
Figure 11.
R =3 0K, 1%
Table 3
- 25 -
R =30K, 1%
C =330 0pF
C =3300pF
TM
Publication Release Date: April 14, 2006
thermal diode interface or transistor
V R EF
P IIT D x
P IIT D x
W 83791D
W83791D/G
TM
D- is connected to
Revision 1.1