w83627ehf Winbond Electronics Corp America, w83627ehf Datasheet - Page 35

• Manufacturer Part Number: w83627ehf
• Description: W83627ehf/ef W83627ehg/eg Winbond Lpc I/o
• Manufacturer: Winbond Electronics Corp America

6.4
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 +3.3V. If the input signals from
the tachometer outputs are over the +3.3V, 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 6.4.
Determine the fan counter according to:
In other words, the fan speed counter has been read from register Bank0 Index 28h, 29h, 2Ah ,3Fh
and Bank5 53h, the fan speed can be evaluated by the following equation.
The default divisor is 2 and defined at Bank0 Index 47h.bit7~4, Index 4Bh.bit7~6, Index 4Ch.bit7,
Index 59h.bit7.bit3~2 and Index 5Dh.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, RPM, and count.
2 (default)
DIVISOR
FAN Speed Count and FAN Speed Control
128
16
32
64
1
4
8
Fan speed count
NOMINAL
8800
4400
2200
1100
RPM
550
275
137
68
REVOLUTION
109.08 ms
218.16 ms
436.32 ms
872.64 ms
Count
TIME PER
RPM
13.64 ms
27.27 ms
54.54 ms
6.82 ms
W83627EHF/EF, W83627EHG/EG
Count
Table 6.2
RPM
1 35 10
-29-
. 1
.
35
u
u
u
COUNTS
u
Divisor
Divisor
10
153
153
153
153
153
153
153
153
6
6
Publication Release Date: January 18, 2006
70% RPM
6160
3080
1540
770
385
192
96
48
1246.72 ms
155.84 ms
311.68 ms
623.36 ms
TIME FOR
19.48 ms
38.96 ms
77.92 ms
9.84 ms
Revision 1.0
70%