4-Wire Pulse Width Modulation (PWM) Controlled Fans Specification

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Contents
1
Introduction .........................................................................................................................7
1.1 Overview................................................................................................................. 7
2 Electrical Specifications ......................................................................................................9
2.1 Fan Requirements..................................................................................................9
2.1.1 Fan Input Voltage.................................................................................... 9
2.1.2 Current....................................................................................................9
2.1.3 Tachometer Output Signal......................................................................9
2.1.4 PWM Control Input Signal ......................................................................9
2.2 Test Methodology.................................................................................................10
2.3 Hardware Monitor Device.....................................................................................10
2.3.1 PWM Output Signal ..............................................................................10
2.4 Considerations for Motherboard Designers .........................................................11
3 Fan Speed Control............................................................................................................ 13
3.1 Maximum Fan Speed Requirements.................................................................... 13
3.2 Minimum Fan Speed Requirements..................................................................... 13
3.3 Fan Speed Response to PWM Control Input Signal............................................14
3.4 Operation below Minimum RPM...........................................................................14
4 Required Features ............................................................................................................19
4.1.1 Polarity Protection.................................................................................19
4.1.2 Rotor Lock Protection ...........................................................................19
4.1.3 Wire Length........................................................................................... 19
4.1.4 Wire Type..............................................................................................19
4.1.5 Connector Housing...............................................................................19
4.1.6 Fan Connector Pinout and Wiring Colors.............................................19
5 Environmental and Reliability............................................................................................ 21
5.1.1 Operating Temperature ........................................................................21
5.1.2 Non-operating Humidity........................................................................21
5.1.3 Non-operating Thermal Cycling............................................................21
5.1.4 Power Cycling....................................................................................... 21
5.1.5 Reliability...............................................................................................21
6 Reference Drawings .........................................................................................................23