EMC2101-R-ACZL-TR datasheet(19/57 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

SMSC EMC2101

Revision 2.54 (06-16-09)

DATASHEET

Chapter 5 General Description

The EMC2101 is an environmental monitoring device with a selectable PWM or DAC fan driver output,

one external temperature monitoring channel and one internal temperature monitor. It contains

advanced circuitry to remove errors induced by series resistance and CPU thermal diode process

differences to provide accurate temperature measurements and accurate fan control.

Thermal management is performed automatically. The EMC2101 reads the temperature from both the

external and internal temperature diodes and uses the external temperature data to control the fan

speed.

The FAN output can be configured as a PWM (default) or DAC output. The PWM fan driver uses an

eight entry look up table to create a programmable temperature response. The DAC output provides

a linear drive for the system fan circuit using this same look up table.

Each temperature measurement channel is continuously compared against programmed high limits.

The external diode channel is compared against a programmed low limit. ALERT / TACH interrupt pin

is asserted if the measured value exceeds the high limit or drops below the low limit. In addition, the

external diode contains a programmable critical temperature, TCRIT. If the measured temperature

exceeds this TCRIT an interrupt is asserted on the ALERT / TACH pin and the fan is set to full on.

Finally, the EMC2101-R (only) has two configuration modes and two default fan settings based on the

value of the pull-up-resistor on the ALERT / TACH pin. In the Manual Configuration Mode, the device

acts as an SMBus client and waits to be configured by the system SMBus host. In the Automatic

Configuration mode, the device automatically queries the SMBus for an EEPROM device and uploads

configuration information from the EEPROM into its internal registers.

Figure 5.1 shows a system level block diagram of the EMC2101. Figure 5.2 shows a system level block

diagram of the EMC2101-R.

Figure 5.1 System Diagram for EMC2101

HOST

SMBus

Interface

SMDATA

Thermal

diode

EMC2101

SMCLK

FAN

ALERT

Fan Drive

Circuitry

Internal

Diode

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