EMC2103 datasheet(21/84 Pages) SMSC

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RPM-Based Fan Controller with HW Thermal Shutdown

Datasheet

SMSC EMC2103

Revision 0.85 (01-29-08)

DATASHEET

5.1

Critical/Thermal Shutdown

The EMC2103 provides a hardware Critical/Thermal Shutdown function for systems. Figure 5.2 is a

block diagram of this Critical/Thermal Shutdown function. The Critical/Thermal Shutdown function

accepts configuration information from the fixed states of the SHDN_SEL pin as described in

Section 5.1.1.

Each of the software programmed temperature limits can be optionally configured to act as inputs to

the Critical / Thermal Shutdown independent of the hardware shutdown operation. When configured to

operate this way, the SYS_SHDN# pin will be asserted when the temperature meets or exceeds the

limit. The pin will be released when the temperature drops below the limit however the individual status

bits will not be cleared if set (see Section 6.13).

The analog portion of the Critical/Thermal Shutdown function monitors the hardware determined

shutdown channel (see Section 5.1.1). This measured temperature is then compared with TRIP_SET

point. This TRIP_SET point is set by the system designer with a single external resistor divider as

described in Section 5.1.2.

The SYS_SHDN is asserted when the indicated temperature meets or exceeds the temperature

threshold (TP) established by the TRIP_SET input pin for a number of consecutive measurements

defined by the fault queue. If the HW_SHDN output is asserted and the temperature drops below the

threshold, then it will be set to a logic ‘0’ state.

Figure 5.2 Block Diagram of Critical / Thermal Shutdown

Temperature

Conversion

HW_SHDN

H/W Thermal

Shutdown Sensor

Critical / Thermal Shutdown

SMBus

Traffic

SW_SHDN

SYS_SHDN

Temperature

Conversion

Software

Shutdown Enable

TRIP_SET

Resistor

Decode

VDD

SHDN_SEL

EMC2103 Datasheet(PDF) 21 Page - SMSC Corporation

EMC2103 Datasheet(HTML) 21 Page - SMSC Corporation

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