RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
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Figure 6.5 Ramp Rate Control
6.10
Watchdog Timer
The EMC2113 contains an internal Watchdog Timer for the fan driver. The Watchdog timer monitors
the SMBus traffic for signs of activity and works in two different modes based upon device operation.
These modes are Power Up Operation and Continuous Operation as described below.
For either mode of operation, if four (4) seconds elapse without activity detected by the host, then the
watchdog will be triggered and the following will occur:
1. The WATCH status bit will be set which will cause the ALERT pin to be asserted.
2. The fan driver will be set to full scale drive. It will remain at full scale drive until it is disabled.
APPLICATION NOTE: When the Watchdog timer is activated the Fan Speed Control Algorithm is automatically
disabled. Disabling the Watchdog will not automatically set the fan drive nor re-activate the
Fan Speed Control Algorithm. This must be done manually.
6.10.1
Power Up Operation
The Watchdog Timer only starts immediately after power-up and once it has been triggered or
deactivated will not restart although it can be configured to operate in Continuous operation.
In the Power Up Operation, the Watchdog Timer is disabled by any of the following actions:
1. Writing the Fan Setting Register will disable the Watchdog Timer.
2. Enabling the RPM-based Fan Speed Control Algorithm by setting the EN_ALGO bit will disable the
Watchdog Timer. The fan driver will be set based on the RPM-based Fan Speed Control Algorithm.
3. Changing the Watchdog operating mode by setting the WD_EN bit.
Writing any other configuration registers will not disable the Watchdog Timer upon power up.
SMSC EMC2113
Revision 1.2 (10-08-09)
DATA3S3HEET
SMSC [ SMSC CORPORATION ]
