W83792G Nuvoton Technology Corporation of America, W83792G Datasheet - Page 26

• 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

7.7
7.7.1
W83792D/G support 6 sets of fan counting. Fan inputs are provided for signals from fans equipped
with tachometer outputs. The level of these signals should be set to TTL level, and the maximum input
voltage should not be over +5.5V. If the input signals from the tachometer outputs are over the VCC,
the external trimming circuit should be added to reduce the voltage to meet the input specification. The
normal circuit and trimming circuits are shown as Figure 8.
Determine the fan counter according to:
In other words, if the fan speed counter has been read from register CR [28], CR [29], CR [2A], CR
[B8], CR [B9] or CR [BA] , then the fan speed can be evaluated by the following equation.
The default divisor is 2 and defined at CR47, CR5B, and CR5C which are three bits for divisor. This
provides very low speed fan counter such as power supply fan. The followed table is an example for
the relation of divisor, RPM, and count.
FAN Speed Count and FAN Speed Control
2 (default)
Fan speed count
DIVISOR
128
16
32
64
1
4
8
NOMINAL RPM
8800
4400
2200
1100
550
275
137
68
RPM
Count
=
=
Count
RPM
Table 2.
- 20 -
. 1
. 1
35
35
×
×
×
×
Divisor
Divisor
10
10
REVOLUTION
109.08 ms
218.16 ms
436.32 ms
872.64 ms
TIME PER
13.64 ms
27.27 ms
54.54 ms
6
6
6.82 ms
W83792AD/AG/D/G
COUNTS
153
153
153
153
153
153
153
153