W83627EHG Nuvoton Technology Corporation of America, W83627EHG Datasheet - Page 51

• Manufacturer Part Number: W83627EHG
• Description: IC I/O CONTROLLER 128-QFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83627EHG

• Applications: PC's, PDA's
• Interface: LPC
• Voltage - Supply: 3.3V
• Package / Case: 128-XFQFN
• Mounting Type: Surface Mount
• Pin Count: 128
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.4
7.4.1
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
7.4.
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
16
32
64
FAN Speed Count and FAN Speed Control
1
4
8
Fan speed count
Nominal
8800
4400
2200
1100
RPM
550
275
137
Revolution
109.08 ms
218.16 ms
436.32 ms
Count
RPM
13.64 ms
27.27 ms
54.54 ms
Time per
6.82 ms
=
=
W83627EHF/EF, W83627EHG/EG
Count
RPM
- 40 -
1 35 10
. 1
.
35
×
×
×
×
Divisor
Counts
Divisor
10
153
153
153
153
153
153
153
6
6
70% RPM
6160
3080
1540
770
385
192
96
Time for 70%
155.84 ms
311.68 ms
623.36 ms
19.48 ms
38.96 ms
77.92 ms
9.84 ms