RPM-Based Fan Controller with HW Thermal Shutdown
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.
SMBus
Critical / Thermal Shutdown
Traffic
Temperature
Conversion
Software
Shutdown Enable
VDD
H/W Thermal
Shutdown Sensor
Resistor
Decode
SHDN_SEL
SW_SHDN
Temperature
Conversion
SYS_SHDN
HW_SHDN
TRIP_SET
Figure 5.2 Block Diagram of Critical / Thermal Shutdown
SMSC EMC2103
Revision 0.85 (01-29-08)
DATA2S1HEET
SMSC [ SMSC CORPORATION ]
