f75373 Feature Integration Technology Inc., f75373 Datasheet - Page 13

• Manufacturer Part Number: f75373
• Description: Fintek Hardware Monitor Ic Datasheet
• Manufacturer: Feature Integration Technology Inc.

5.4.2
The F75373S provides 2 fan PWM speed control. The duty cycle of PWM can be programmed by a 8-bit register which are
defined in the CR76h and CR86h. The default duty cycle is set to 100%, that is, the default 8-bit registers is set to FFh. The
expression of duty can be represented as follows.
Determine the fan counter according to:
In other words, the fan speed counter has been read from register, the fan speed can be evaluated by the following equation. As
for fan, it would be best to use 2 pulses tachmeter output per round.
Fintek
PWM Clock Input
Fan speed control
Figure 5-7. Fan with Tach Pull-Up to +5V, or Totern-Pole
FAN Out
+5V
GND
+5V
Output and Register Attenuator
Duty_cycle
G
D
S
R1
NMOS
Figure 5-9
Pull-up resister
4.7K Ohms
1K~2.7K
+12V
R2
(%)
Fan Input
10K
=
+
-
Programmed
PNP Transistor
FANIN1
F75373S
C
Count
RPM
FAN
=
8
1 ×
5 .
- 8
=
RPM
255
1 ×
bit
5 .
Count
10
Connector
PWM Clock Input
Feature Integration Technology Inc.
Register
6
FAN
.Figure 5-8 Fan with Tach Pull-Up to +5V, or
10
FAN Out
6
+5V
GND
+5V
Value
Totem-Pole Putput and Zener Clamp
G
D
S
R1
NMOS
×
Figure 5-10
Pull-up resister < 1K
or totem-pole output
100
3.3V Zener
> 1K
+5V
%
R2
Fan Input
+
-
F75373
PNP Transistor
C
FANIN1
F75373S
FAN
V0.25P