On the computer motherboard, or many boards, there will be a fan interface, usually 4P, including GND, VCC, PWM, TACH (speed).
VCC: Provide the corresponding voltage according to the fan specification, generally 12V, plus the energy storage filter capacitor.
GND: Current return.
PWM: Generally connected to the PWM pin of MCU or EC or BMC, isolated by MOS, and output frequency signal related to speed.
TACH: Fan speed feedback signal, through BAT54C to achieve voltage stabilization and protection.
In addition, it is recommended to connect fuses in series for the external interface power supply, and it is recommended to add magnetic beads to isolate interference for distributed power supply loads.
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