Auto Fan Device with Piecewise Linear Control, Temperature Monitoring & Voltage Monitoring for Multi-

Processor Systems

SMSC EMC6W201

3

Revision 0.3 (03-01-07)

PRODUCT PREVIEW

General Description

The EMC6W201 is an environmental monitoring device with automatic fan control capability and

enhanced system acoustics for noise suppression. This ACPI compliant device provides hardware

monitoring for up to six voltages (including its own VCC) and five external thermal sensors, measures

the speed of up to five fans, and controls the speed of multiple DC fans using three Pulse Width

Modulator (PWM) outputs. Note that it is possible to control more than three fans by connecting two

fans to one PWM output. The EMC6W201 will be available in a 36-pin QFN, lead-free RoHS Compliant

package.

The EMC6W201 includes support for monitoring six thermal sensors: five external and one internal.

The external temperatures are measured via thermal diode inputs capable of monitoring remote

devices. In addition, it is equipped with an ambient temperature sensor for measuring the internal

temperature.

The EMC6W201 hardware monitor provides analog inputs for monitoring external voltages of +1.5V,

+2.5V, +5V, and two Vccp voltages. This device has the capability to monitor its own internal VCC

power supply, which may be connected to either main power (VCC) or the suspend power well (VTR).

External components are not required for voltage scaling or similar treatment.

Pulse Width Modulators (PWM) will control the speed of the fans by varying the output duty cycle of

the PWM. The Ramp Rate Control feature controls the rate of change of the PWM output, thereby

reducing system noise created by changing the fan speed. The speed of each fan is monitored by a

Fan Tachometer input. The measured values are compared to values stored in Limit Registers to

detect if a fan has stalled or seized.

Fan speed may be under host software control or automatic. In host control mode, the host software

continuously monitors temperature and fan speed registers, makes decisions as to desired fan speed

and sets each PWM to drive the required fan speed. The PWM frequency is adjustable up to 30kHz.

The EMC6W201 device offers an interrupt output signal (INT#), which may be used to interrupt the

host on out-of-limit temperature or voltage condition enabling an ACPI response as opposed to the

host software continuously monitoring status.

In auto “zone” mode, the EMC6W201 logic continuously monitors the temperature and fan speeds and

adjusts speeds without intervention from the host CPU. Fan speed is adjusted according to an

algorithm using the temperature measured in the selected zone, the high and low limits set by the user,

and the current fan speed. The part can automatically adjust its operation based on its environment

for improved acoustic behavior.

Overview

The EMC6W201 device is an intelligent fan control system with reduced overall acoustic noise

features. The EMC6W201 monitors voltages, external temperatures, and fan speeds. It uses this

monitoring capability to alert the system to out of limit conditions and can automatically control the

speeds of multiple fans.