W83697HG-TR Nuvoton Technology Corporation of America, W83697HG-TR Datasheet - Page 28

• Manufacturer Part Number: W83697HG-TR
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83697HG-TR

• Lead Free Status / RoHS Status: Supplier Unconfirmed

6.4 FAN Speed Count and FAN Speed Control
6.4.1
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
9.4.
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.
Fan speed count
Pentium II
Bipolar Transistor
Temperature Sensor
Therminal
B
Diode
CPU
OR
C
E
2N3904
D+
D-
RPM
Count
=
=
Count
Figure 9.3
R=30K, 1%
RPM Divisor
1 35 10
- 25 -
1 35 10
.
.
R=30K, 1%
×
×
×
×
C=3300pF
Divisor
C=3300pF
6
6
VREF
VTINx
VTINx
Publication Release Date: May 30, 2005
W83627HF
W83697HF/ HG
Revision A1