W83L784R_05 Datasheet, PDF (17/52 Pages) Winbond – Monitoring IC

W83L784R/ W83L784G
6.4.1 Monitor temperature from thermistor:
The W83L784R/G can connect three thermistors to measure three different envirment temperature.
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 10, the themistor is connected by a serial resistor with 10K Ohms, and
then connect to VREF (pin 17).
6.4.2 Monitor temperature from Pentium IITM thermal diode or bipolar transistor 2N3904
The W83L784R/G can alternate the thermistor to Pentium II^TM (Deschutes) thermal diode interface or
transistor 2N3904 and the circuit connection is shown as Figure 12. The pin of Pentium II^TM D- is
connected to power supply ground (GND) and the pin D+ is connected to pin PIIx in the W83L784R/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.
Bipolar Transistor
Temperature Sensor
C
B _2N3904
E
OR
Pentium II
CPU
D+
Therminal
Diode
D-
R=30K, 1%
VREF
PIITDx
C=3300pF
R=30K, 1%
W83L784R
PIITDx
C=3300pF
Figure 12
6.4.3 Over Temperature
W83L784R/G provides two external thermal sensors to detect temperature. When detected
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.
6.4.3.1. ACPI Mode
At this mode, temperature exceeding one level of temperature separation, 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
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Publication Release Date: Jan. 2005
Revision 1.1