w83l784r Winbond Electronics Corp America, w83l784r Datasheet - Page 19

• Manufacturer Part Number: w83l784r
• Description: Winbond H/w Monitoring Ic
• Manufacturer: Winbond Electronics Corp America

6.4.2 Monitor temperature from Pentium II
The W83L784R can alternate the thermistor to Pentium II
transistor 2N3904 and the circuit connection is shown as Figure 12. The pin of Pentium II
connected to power supply ground (GND) and the pin D+ is connected to pin PIIx in the W83L784R.
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 togeter to act as a thermal diode.
6.4.3 Over Temperature
6.4.3.1 ACPI Mode :
Confidential, For Beta-site Only
temperature exceeds the over-temperature value, pin OVT# will be asserted until the
temperature goes below the hysteresis temperature. Pin OVT# has 3 operating modes:
At this mode, temperature exceeding one level of temperature sepeartion , starting from 0
degree, causes the OVT# output activated. OVT# will be activated again once temperature
exceeding the next level. OVT# output will act the same manner when temperature goes down.
(Figure 13). The granularity of temperature separation between each OVT# output signal can be
programmed at Bank0 CR[4Fh].
The piority of this mode is higher than Comparator mode and Interrupt mode .
W83L784R provides two external thermal sensors to detect temperature. When detected
Temperature Sensor
Bipolar Transistor
Pentium II
Therminal
CPU
Diode
B
OR
C
E
2N3904
D+
D-
TM
-18 -
Figure 12.
R=30K, 1%
thermal diode or bipolar transistor 2N3904
R=30K, 1%
C=3300pF
C=3300pF
TM
(Deschutes) thermal diode interface or
VREF
PIITDx
PIITDx
W83L784R
Publication Release Date: Sep.
W83L784R
Preliminary
Revision 0.54
TM
D- is
1999