COM Express Interfaces
2.22.8. Fan Connector
Figure 57: Fan Connector Reference Schematic
FAN_TACHIN and FAN_PWMOUT in Figure 57: Fan Connector Reference Schematic above are
COM.0 pins reclaimed from the VCC_12V pool. Q13 / Q14 and U34 / U35 are the necessary
circuitry on the Carrier Board to handle the 12V protection according to chapter 2.22.10
'Protecting COM.0 Pins Reclaimed From the VCC_12V Pool' on page 144 below. This reference
schematic shows a 4-wire fan implementation, which should be preferred over a 3-wire fan. 4-
wire fan implementations allow better sensing and control of the fan.
PICMG
®
COM Express
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Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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