W83781D Nuvoton Technology Corporation of America, W83781D Datasheet - Page 16

• Manufacturer Part Number: W83781D
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83781D

• Lead Free Status / Rohs Status: Supplier Unconfirmed

The value of R
voltage is 12V. The Pin 33 is connected to +5V power supply to provide analog power, and this
voltage is connected to internal resistors to monitor the +5V voltage.
The negative voltage should be connected an op amps to invert and reduce the -5V and -12V voltage.
The input voltage can be calculated by following equation.
The Winbond recommended value is R
R
The temperature sensors are connected by a 10K Ohms, then connect to VREF (Pin 37). The sensors
should choose 10K Ohms at 25°C and β-value is 3435 for default R-T table. If the β-value is not 3435,
the R-T table should be re-program to generate a correct temperature.
7.3 FAN Inputs and FAN Control
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
following.
Determine the fan counter according to:
The default divisor is 2 and defined at CR47.bit7~4 and CR4B.bit7~6. The followed table is an
example for the relation of divisor, PRM, and count.
IN
=210K Ohms and R
DIVISOR
1
2
4
8
1
and R
NOMINAL
8800
4400
2200
1100
PRM
F
2
=60.4K Ohms for -12V voltage input.
can be selected to 28K Ohms and 10K Ohms, respectively, when the input
REVOLUTION
TIME PER
13.64 ms
27.27 ms
54.54 ms
6.82 ms
Count
V
IN
V
=90.9K Ohms and R
S
IN
= −
=
=
V
V
RPM Divisor
s
- 12 -
IN
×
135 10
.
× (
R
×
1
×
COUNTS
R
+
R
R
2
IN
F
R
153
153
153
153
6
2
)
F
Publication Release Date: April 14, 2005
=60.4K Ohms for -5V voltage input,
W83781D/W83781G
70% RPM
6160
3080
1540
770
TIME FOR 70%
19.48 ms
38.96 ms
77.92 ms
9.74 ms
Revision 2.0