RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
3. Setting the LUT_LOCK bit will disable the Watchdog Timer. The fan driver will be set based on the
Look Up Table settings.
Writing any other configuration registers will not disable the Watchdog Timer.
APPLICATION NOTE:
Disabling the Watchdog will not automatically set the fan drive. This must be done manually
(or via the Look Up Table).
5.10
Fault Queue
The EMC2103 contains a programmable fault queue on all fault conditions. The fault queue defines
how many consecutive out-of-limit conditions must be reported before the corresponding status bit is
set (and the ALERT pin asserted).
5.11
Temperature Monitoring
The EMC2103 can monitor the temperature of up to three (3) externally connected diodes as well as
the internal or ambient temperature. Each channel is configured with the following features enabled or
disabled based on user settings and system requirements.
5.11.1
Dynamic Averaging
The EMC2103 supports dynamic averaging. When enabled, this feature changes the conversion time
for all channels based on the selected conversion rate. This essentially increases the averaging factor
as shown in
The benefits of Dynamic Averaging are improved noise rejection due to the
longer integration time as well as less random variation on the temperature measurement.
Table 5.4 Dynamic Averaging Behavior
AVERAGING FACTOR (RELATIVE TO 11-BIT CONVERSI0N)
CONVERSION RATE
DYNAMIC AVERAGING
ENABLED
8x
4x
2x
1x
DYNAMIC AVERAGING
DISABLED
1x
1x
1x
1x
1 / sec
2 / sec
4 / sec
Continuous
5.11.2
Resistance Error Correction
The EMC2103 includes active Resistance Error Correction to remove the effect of up to 100 ohms of
series resistance. Without this automatic feature, voltage developed across the parasitic resistance in
the remote diode path causes the temperature to read higher than the true temperature is. The error
induced by parasitic resistance is approximately +0.7°C per ohm. Sources of parasitic resistance
include bulk resistance in the remote temperature transistor junctions, series resistance in the CPU,
and resistance in the printed circuit board traces and package leads. Resistance error correction in the
EMC2103 eliminates the need to characterize and compensate for parasitic resistance in the remote
diode path.
Revision 0.85 (01-29-08)
32
SMSC EMC2103
DATASHEET
SMSC [ SMSC CORPORATION ]
