emc2105 Standard Microsystems Corp., emc2105 Datasheet - Page 35

• Manufacturer Part Number: emc2105
• Description: Emc2105 Rpm-based High Side Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

RPM-Based High Side Fan Controller with Hardware Thermal Shutdown
Datasheet
APPLICATION NOTE: When the fan driver is disabled via a thermal shutdown event, the drive settings will not be
APPLICATION NOTE: With the exception of the Tcrit limit, the fault queue is not applied to the internal diode
APPLICATION NOTE: When measuring an Intel 45nm CPU, the reported temperature will have an error of
SMSC EMC2105
5.10
5.11
5.12
5.12.1
CONVERSION RATE
The EMC2105 contains an internal thermal shutdown circuit that monitors the internal die temperature.
If the die temperature exceeds the Thermal Shutdown Threshold (see
will occur:
1. The High Side Fan Driver is disabled. It will remain disabled until the internal temperature drops
2. The TSD Status bit will be set and the SYS_SHDN# pin asserted.
3. The SYS_SHDN# pin is asserted.
The EMC2105 contains a programmable fault queue on all fault conditions except a FAN_SHORT or
TSD condition (including all temperature high, low, and tcrit limits as well as the hardware set thermal
limit). 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).
The EMC2105 can monitor the temperature of up to four (4) 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.
Dynamic Averaging
The EMC2105 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
longer integration time as well as less random variation on the temperature measurement.
Internal Thermal Shutdown (TSD)
Fault Queue
Temperature Monitoring
below the threshold temperature minus 50°C.
1 / sec
2 / sec
4 / sec
8 / sec
altered. Thus, when the temperature drops below the threshold minus the hysteresis, the fan
will return to its previous drive setting.
measurement.
approximately 1.5°C at 100°C. This error is related to a non-perfect ideality factor of the CPU
diode and is proportional to the diode temperature.
Table
5.4. The benefits of Dynamic Averaging are improved noise rejection due to the
Table 5.4 Dynamic Averaging Behavior
DATASHEET
AVERAGING FACTOR (RELATIVE TO 11-BIT CONVERSI0N)
DYNAMIC AVERAGING
35
ENABLED
8x
4x
2x
1x
Table
DYNAMIC AVERAGING
3.2), then the following
Revision 1.74 (05-08-08)
DISABLED
1x
1x
1x
1x