W83782G Nuvoton Technology Corporation of America, W83782G Datasheet - Page 17

• Manufacturer Part Number: W83782G
• Description: IC MONITOR H/W 48-LQFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83782G

• Output Type: I²C™, ISA
• Function: Hardware Monitor
• Topology: ADC, Fan Speed Counter, Register Bank
• Sensor Type: External
• Sensing Temperature: External Sensor
• Output Alarm: No
• 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
• Temperature Sensor Function: Temp Sensor
• Operating Temperature (min): -40C
• Operating Temperature (max): 120C
• Operating Supply Voltage (typ): 5V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.4 FAN Speed Count and FAN Speed Control
6.4.1 Fan speed count
Inputs are provides for signals from fans equipped with tachometer outputs. The level of these signals
should be set to TTL level, and maximum input voltage can 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 obtain the input specification. The normal circuit and trimming circuits are shown as Figure
13.
Determine the fan counter according to:
In other words, the fan speed counter has been read from register CR28 or CR29 or CR2A, the fan
speed can be evaluated by the following equation.
The default divisor is 2 and defined at CR47.bit7~4, CR4B.bit7~6, and Bank0 CR5D.bit5~7 which are
three bits for divisor. That provides very low speed fan counter such as power supply fan. The
followed table is an example for the relation of divisor, PRM, and count.
2 (default)
DIVISOR
128
16
32
64
1
4
8
Count
RPM
NOMINAL
8800
4400
2200
1100
=
PRM
=
550
275
137
68
RPM Divisor
Count
135 10
.
135 10
.
×
×
×
×
Divisor
6
REVOLUTION
6
109.08 ms
218.16 ms
436.32 ms
872.64 ms
TIME PER
13.64 ms
27.27 ms
54.54 ms
6.82 ms
Table 1
- 14 -
COUNTS
153
153
153
153
153
153
153
153
W83782D/W83782G
70% RPM
6160
3080
1540
770
385
192
96
48
TIME FOR 70%
1246.72 ms
155.84 ms
311.68 ms
623.36 ms
19.48 ms
38.96 ms
77.92 ms
9.74 ms