NA of Moles

ATX

It turns out that the PWM signal on PC fans doesn’t require much current. Max 5mA according to the Intel specifications.

2.1.4 PWM Control Input Signal from the Intel specification
2.1.4 PWM Control Input Signal from the Intel specification

Source

The trick is to place a driver inside the fan capable of obtaining the necessary voltage/current.

Schematics for the driver circuit inside the fan
Schematics for the driver circuit inside the fan

Source

This exonerates the MoBo engineers from accounting for high current requirements when designing the PWM controller and avoids wasting energy driving up and down a potentially high current through the connectors and cables.

Tags: #ATX #Electronics