资料介绍
The NLX Power Supply Specification released by Intel
®
Corporation defines the requirements for next-genera-
tion PC system power supplies. There are several
enhancements outlined in this specification as com-
pared to the “old” PS/2 power supply form factor. One of
these features is control and monitoring of the cooling
fan(s) inside the NLX power supply. The NLX specifica-
tion designates two interface fan control signals:
1. FanM signal is an output from the NLX-compli-
ant power supply. This signal allows the host
(typically a system management ASIC) to moni-
tor fan RPM. FanM is an open-collector signal
consisting of two pulses per fan rotation.
2. FanC is an input to the NLX-compliant power
supply used by the motherboard to regulate fan
speed and to shut the fan down. FanC is a 0V to
12V analog signal.M AN764
Implementing Temperature-Based Variable Fan Speed
Control in NLX Power Supplies
1. Linear Voltage Control: This method varies the
Author: Microchip Technology Inc.
DC voltage at the VDD terminal of the fan in a lin-
ear manner. For example, a +12V nominal fan
INTRODUCTION modulated linearly to +8V would theoretically
run at 66.7% RPM. Though this seems rel
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