W83627UHG Nuvoton Technology Corporation of America, W83627UHG Datasheet - Page 51

• Manufacturer Part Number: W83627UHG
• Description: IC I/O CONTROLLER 128-QFP
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83627UHG

• Applications: PC's, PDA's
• Interface: LPC
• Voltage - Supply: 3.3V, 5V
• Package / Case: 128-XFQFN
• Mounting Type: Surface Mount
• Pin Count: 128
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.6
This section is divided into two parts, one to measure the speed and the other to control the speed.
7.6.1
The W83627UHG can measure fan speed for fans equipped with tachometer outputs. The tachometer
signals should be set to TTL-level, and the maximum input voltage cannot exceed +5 V. If the
tachometer signal exceeds +5 V, an external trimming circuit should be added to reduce the voltage
accordingly.
The fan speed counter is read from Bank0 Index 28h, and 29h. The fan speed can then be evaluated
by the following equation:
The default divisor is 2 and is specified at Bank0 Index 47h, bits 7 ~ 4; and Index 5Dh, bits 6 ~ 5.
There are three bits for each divisor, and the corresponding divisor is listed in the table below.
The following table provides some examples of the relationship between divisor, RPM, and count.
BIT 2
2 (default)
DIVISOR
0
0
0
0
Fan Speed Measurement and Control
128
16
32
64
1
4
8
Fan Speed Measurement
BIT 1
0
0
1
1
NOMINAL
8800
4400
2200
1100
RPM
BIT 0
550
275
137
68
0
1
0
1
Table 7-5 Divisor, RPM, and Count Relation
FAN DIVISOR
REVOLUTION
Table 7-4 Fan Divisor Definition
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
RPM
1
2
4
8
=
Count
-40-
. 1
35
COUNTS
BIT 2
×
×
Divisor
1
1
1
1
153
153
153
153
153
153
153
153
10
6
BIT 1
0
0
1
1
70% RPM
6160
3080
1540
770
385
192
96
48
BIT 0
0
1
0
1
W83627UHG
FAN DIVISOR
TIME FOR 70%
1246.72 ms
155.84 ms
311.68 ms
623.36 ms
19.48 ms
38.96 ms
77.92 ms
9.84 ms
128
16
32
64