mITX-SKL-H – User Guide, Rev.1.1
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8.2.
Fan Connectors (J33, J34)
The system fan connector (J34) can be used to power, control and monitor a fan for chassis ventilation. The CPU fan
connector (J33) is used for the connection of the fan for the CPU. The 4-pin connector is recommended for driving a 4-
wire type fan, in order to implement fan speed control. 3-wire fan support is also possible, but fan speed control is
not integrated.
Figure 12: Fan Connector
Table 14: Pin Assignment 4-Pin Fan Support Mode
Pin
Signal
Description
Type
1
GND
Ground
PWR
2
12 V
Power +12 V
PWR
3
TACHO
Tacho signal
I
4
PWM
PWM Output
O-3.3
Table 15: Pin Assignment 3-Pin Fan Support Mode
Pin
Signal
Description
Type
1
GND
Ground
PWR
2
12 V
Power +12 V
PWR
3
TACHO
Tacho signal
I
4
NC
NC
Signal Description
Signal
Description
Type
GND
Power Supply GND signal
PWR
12 V
+12 V supply for fan. A maximum of 600 mA can be supplied from this pin.
PWR
TACHO
Tacho input signal from the fan, for rotation speed supervision RPM (Rotations Per
Minute). The signal shall be generated by an open collector transistor or similar.
A 4.7
Ω
pull-up resistor to +12 V is on-board. The signal has to be pulsed and the on-board
circuit is prepared for two pulses per rotation.
I
PWM
PWM output signal for FAN speed control
O
