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W83791D Datasheet, PDF (32/46 Pages) Winbond – W83791D Winbond H/W Monitoring IC
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W83791D
Preliminary
6.8
Temperature Measurement Machine
The temperature data format is 8-bit two-complement for sensor 1 and 9-bit two-complement for sensor 2/3.
The 8-bit temperature data can be obtained by reading the CR[27h]. The 9-bit temperature data can be obtained by
reading the 8 MSBs from the bank0 CR[C0/ C8h] and the LSB from the bank0 CR[C1/C9h] bit 7. The format of
the temperature data is show in Table 3.
Temperature
+125°C
+25°C
+1°C
+0.5°C
+0°C
-0.5°C
-1°C
-25°C
-55°C
8-Bit Digital Output
8-Bit Binary
8-Bit Hex
0111,1101
7Dh
0001,1001
19h
0000,0001
01h
-
-
0000,0000
00h
-
-
1111,1111
FFh
1110,0111
E7h
1100,1001
C9h
Table 3.
9-Bit Digital Output
9-Bit Binary
9-Bit Hex
0,1111,1010
0FAh
0,0011,0010
032h
0,0000,0010
002h
0,0000,0001
001h
0,0000,0000
000h
1,1111,1111
1FFh
1,1111,1110
1FFh
1,1100,1110
1CEh
1,1001,0010
192h
6.8.1 Monitor temperature from thermistor:
The W83791D 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 Monitor temperature from Pentium IITM thermal diode or bipolar transistor 2N3904
The W83791D can alternate the thermistor to Pentium II/IIITM thermal diode interface or transistor 2N3904
and the circuit connection is shown as Figure 11. The pin of Pentium II/IIITM D- is connected to power supply
ground (GND) and the pin D+ is connected to pin PIITDx in the W83791D. 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.
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Publication Release Date: Aug, 2001
Revision 0.41
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