RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
5.7.1
TRIP_SET
The EMC2102’s TRIP_SET pin is an analog input to the Critical/Thermal Shutdown block which sets
the Thermal Shutdown temperature. The system designer creates a voltage level at this input through
a simple resistor divider between the 3.3V supply and GND. This input voltage is valid between 0V
and 1.5V which corresponds to Thermal Shutdown temperature setpoints between 75°C and 106°C as
described in the following equation.
T
TRIP – 75
---------------------------
TRIP_SET Pin Voltage =
Where:
21
T
TRIP is the desired trip point
temperature
[1]
TRIPSET is the voltage on
the TRIP_SET pin
5.7.2
SHDN_SEL Pin
The EMC2102 has one ‘strappable’ input (SHDN_SEL) allowing for configuration of the hardware
Critical/Thermal Shutdown. This pin has 3 possible states and is monitored and decoded by the
EMC2102 at power-up. The three possible states are 0 (tied to GND), 1 (tied to 3.3V) or High-Z (open).
The states of this pin determine which remote temperature channel and configuration is used by the
Critical/Thermal Shutdown function. The different configurations of SHDN_SEL pin are described in
Table 5.4
A channel that is configured via the SHDN_SEL pin for the Critical/Thermal Shutdown is locked and
none of the configuration registers associated with it can be updated via the SMBus. The other two
temperature channels, however, are still configurable via the SMBus.
Table 5.4 SHDN_SEL Pin Configuration
REMOTE CHANNEL
FUNCTION
NAME
INPUT TO THERMAL
SHUTDOWN
SHDN_SEL
CRITICAL/THERMAL SHUTDOWN DETAILS
0
High-Z
1
Intel Mode
Diode Mode
Disabled,
1
3
Channel 1 is configured and locked with both
Beta Compensation and Resistance Error
Correction enabled which is optimized for an
Intel thermal diode.
Channel 3 is configured and locked with
Resistance Error Correction enabled which is
optimal for interfacing a discrete diode-
connected NPN transistor.
NA
The Critical/Thermal Shutdown function will not
assert SYS_SHDN# based on a temperature
channel. This does not include software
configured inputs (see Section 6.4)
Revision 1.95 (10-19-06)
SMSC EMC2102
DATA2S8HEET
SMSC [ SMSC CORPORATION ]
