RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
5.1.1
SHDN_SEL Pin
The EMC2103 has a ‘strappable’ input (SHDN_SEL) allowing for configuration of the hardware
Critical/Thermal Shutdown input channel. The pull-up resistor used on this pin identifies which
configuration setting is used as shown in
.
Table 5.1 SHDN_SEL Pin Decode
PULL UP RESISTOR
MODE OF OPERATION
External Diode 1 Simple Mode -
Beta compensation disabled, REC
disabled - recommended for AMD
CPU diodes
External Diode 1 Diode Mode -
Beta compensation disabled, REC
enabled
External Diode 1 Transistor Mode -
Beta compensation enabled, REC
enabled - recommended for Intel
45nm and 65mn CPU diodes
Internal Diode
External Diode 2 Transistor Mode -
Beta Compensation enabled, REC
enabled (EMC2103-2 only) See
External Diode 1 Transistor Mode -
Beta compensation enabled, REC
enabled
CONFIGURATION MECHANISM
Host control via SMBus
< 4.7k Ohm
Host control via SMBus
6.8k Ohm
Host control via SMBus
10k Ohm
15k Ohm
Host control via SMBus
Host control via SMBus
22k Ohm
Host control via SMBus
> 33k Ohm
Note 5.1
For the EMC2103-1, the decode for a 22k Ohm resistor on the SHDN_SEL pin will be to
use the External Diode 1 channel in Diode Mode (the same as the decode for a 6.8k Ohm
resistor) as the hardware shutdown device.
5.1.2
TRIP_SET Pin
The EMC2103’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 the input through
a simple resistor connected to GND as shown in
The value of this resistor is used to create
an input voltage on the TRIP_SET pin which is translated into a temperature ranging from 65°C to
127°C as shown in
APPLICATION NOTE:
Current only flows when the TRIP_SET pin is being monitored. At all other times, the internal
reference voltage is removed and the TRIP_SET pin will be pulled down to ground.
APPLICATION NOTE:
The TRIP_SET pin circuitry is designed to use a 1% resistor externally. Using a 1% resistor
will result in the Thermal / Critical Shutdown temperature being decoded correctly. If a 5%
resistor is used, then the Thermal / Critical Shutdown temperature may be decoded with as
much as ±1°C error.
Revision 0.85 (01-29-08)
22
SMSC EMC2103
DATASHEET
SMSC [ SMSC CORPORATION ]
