RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Table 5.3 Fan Controls Active for Operating Mode (continued)
DIRECT PWM
SETTING MODE
DIRECT PWM SETTING W/
LUT MODE
FSC MODE
FSC W/ LUT MODE
Valid TACH Count
-
Valid TACH Count
Valid TACH Count
-
Valid TACH Count
TACH Target (read /
write)
TACH Target (read only)
TACH Reading
-
TACH Reading
-
TACH Reading
TACH Reading
Look Up Table Drive /
Temperature Settings (read
only)
Look up Table Drive /
Temperature Settings
(read only)
-
DRIVE_FAIL_CNT [1:0]
(Spin Up Configuration) +
Fan Drive Fail Band
-
DRIVE_FAIL_CNT [1:0]
(Spin Up Configuration)
+ Fan Drive Fail Band
5.3
5.4
PWM Fan Driver
The EMC2103 supports a high or low frequency PWM driver. The output can be configured as either
push-pull or open drain and the frequency ranges from 9.5Hz to 26kHz in four programmable
frequency bands.
Fan Control Look-Up Table
The EMC2103 uses a look-up table to apply a user-programmable fan control profile based on
measured temperature to the fan driver. In this look-up table, each temperature channel is allowed to
control the fan drive output independently (or jointly) by programming up to eight pairs of temperature
and drive setting entries.
The user programs the look-up table based on the desired operation. If the RPM based Fan Speed
Control Algorithm is to be used (see Section 5.5), then the user must program a fan speed target for
each temperature setting of interest. Alternately, if the RPM based Fan Speed Control Algorithm is not
to be used, then the user must program a PWM setting for each temperature setting of interest.
If the measured temperature on the External Diode channel meets or exceeds any of the temperature
thresholds for any of the channels, the fan output will be automatically set to the desired setting
corresponding to the exceeded temperature. In cases where multiple temperature channel thresholds
are exceeded, the highest fan drive setting will take precedence. Figure 5.3 shows an example of this
behavior using a single channel.
When the measured temperature drops to a point below a lower threshold minus the hysteresis value,
the fan output will be set to the corresponding lower set point.
SMSC EMC2103
Revision 0.85 (01-29-08)
DATA2S5HEET
SMSC [ SMSC CORPORATION ]
