F71862
+12V
+12V
Pull-up resister
4.7K Ohms
Pull-up resister < 1K
or totem-pole output
+12V
FAN Out
GND
22K~30K
+12V
FAN Out
GND
Fan Input
10K
> 1K
FANIN 1
Fan Input
FANIN 1
3.3V Zener
F71862
F71862
FAN
Connector
Fan with Tach Pull-Up to +12V, or
Totem-Pole Putput and Zener Clamp
Fan with Tach Pull-Up to +12V, or Totern-Pole
Output and Register Attenuator
Fig 7-4 / 7-5
+5V
+5V
Pull-up resister
4.7K Ohms
Pull-up resister < 1K
or totem-pole output
+5V
1K~2.7K
Fan Input
+5V
> 1K
FAN Out
GND
FANIN1
Fan Input
FAN Out
GND
FANIN1
10K
3.3V Zener
F71862
F71862
FAN
Connector
Fan with Tach Pull-Up to +5V, or
Fan with Tach Pull-Up to +5V, or Totern-Pole
Output and Register Attenuator
Totem-Pole Putput and Zener Clamp
Fig 7-6 / 7-7
Determine the fan counter according to:
1.5×106
Count =
RPM
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
tachometer output per round.
1.5×106
RPM =
Count
Fan speed control
The F71862 provides 2 fan speed control methods:
1. DAC FAN CONTROL 2. PWM DUTY CYCLE
DAC Fan Control
45
July, 2008
V.28P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
