Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
The TACH / DRIVE bit in the Look Up Table Configuration Register MUST be set to ‘0’ or
the TACH Target values will be incorrectly set. Setting this bit to ‘0’ ensures that the settings
will be RPM settings (Tachometer counts).
APPLICATION NOTE:
It is important that the TACH Target settings are in the proper format when using the RPM
based Fan Speed Control Algorithm.
Table 5.3 Fan Controls Active for Operating Mode
DIRECT SETTING
MODE
Fan Driver Setting
(read / write)
EDGES[1:0]
-
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up
Configuration)
SPINUP_TIME[1:0]
(Spin Up
Configuration)
Fan Step
-
Valid TACH Count
-
TACH Reading
-
DIRECT SETTING W/ LUT
MODE
Fan Driver Setting (read
only)
EDGES[1:0]
-
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
Fan Step
FSC MODE
Fan Driver Setting (read
only)
EDGES[1:0]
(Fan Configuration)
RANGE[1:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
Fan Step
Fan Minimum Drive
Valid TACH Count
TACH Target (read / write)
TACH Reading
-
FSC W/ LUT MODE
Fan Driver Setting (read
only)
EDGES[1:0]
RANGE[1:0]
(Fan Configuration)
UPDATE[2:0]
(Fan Configuration)
LEVEL
(Spin Up Configuration)
SPINUP_TIME[1:0]
(Spin Up Configuration)
Fan Step
Fan Minimum Drive
Valid TACH Count
-
TACH Reading
Look Up Table Drive /
Temperature Settings (read
only)
-
Valid TACH Count
TACH Target (read
only)
TACH Reading
Look up Table Drive /
Temperature Settings
(read only)
DRIVE_FAIL_CNT[1:0]
and Drive Band Fail
Registers
-
DRIVE_FAIL_CNT[1:0] and
Drive Band Fail Registers
5.3
PWM Fan Driver
The EMC2104 supports two PWM output drivers. These output drivers can be configured
independently to operate as an open-drain (default) or push-pull driver and can be configured with
normal or inverse polarity. Additionally, the each PWM driver frequency is programmable with ranges
from 9.5Hz to 26kHz in four programmable frequency bands.
5.4
Fan Control Look-Up Table
The EMC2104 uses a look-up table to apply a user-programmable fan control profile based on
measured temperature to each fan driver. In this look-up table, each temperature channel is allowed
Revision 1.74 (05-08-08)
26
SMSC EMC2104
DATASHEET
SMSC [ SMSC CORPORATION ]
