Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Chapter 1 General Description
The EMC6D102 is an environmental monitoring device with automatic fan control capability. This ACPI
compliant device provides hardware monitoring for up to five voltages and three thermal zones,
measures the speed of up to four fans, and controls the speed of multiple DC fans using Pulse Width
Modulator (PWM) outputs.
The EMC6D102 hardware monitor provides analog inputs for monitoring external voltages of +2.5V,
+5V, +12V and Vccp. 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). In addition to
monitoring the processor voltage, VID inputs are available to identify the voltage specification. External
components are not required for voltage scaling or similar treatment.
The EMC6D102 hardware monitor includes support for monitoring three thermal zones: two external
and one internal. The external temperatures are measured via thermal diode inputs capable of
monitoring remote devices. In addition, they are equipped with an ambient temperature sensor for
measuring the internal temperature.
Pulse Width Modulators (PWM) control the speed of the fans by varying the output duty cycle of the
PWM. Each PWM can be associated with any or all of the thermal zones monitored. As the
temperature of the associated zone varies, the PWM duty cycle is adjusted accordingly. 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 the PWM’s to drive the required fan speed. This 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 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.
Revision 0.4 (06-15-06)
DATASHEET
8
SMSC EMC6D102
SMSC [ SMSC CORPORATION ]
