emc2105 Standard Microsystems Corp., emc2105 Datasheet - Page 69

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

ADDR
75h
76h
77h
78h
79h
RPM-Based High Side Fan Controller with Hardware Thermal Shutdown
Datasheet
APPLICATION NOTE: For proper operation, the hysteresis must be smaller than the difference between two
SMSC EMC2105
R/W
R/W
R/W
R/W
R/W
R/W
LUT Temp 3
LUT Voltage
LUT Temp 4
REGISTER
3 Setting 8
LUT Temp
Hysteresis
LUT VIN1
LUT VIN2
Setting 8
Setting 8
Setting 8
Setting 8
Setting 8
Setting 8
LUT Ext
LUT Ext
Diode 1
Diode 2
The Look Up Table Registers hold the 40 entries of the Look Up Table that controls the drive of the
Fan. As the temperature (or voltage) channels are updated, the measured value for each channel is
compared against the respective entries in the Look Up Table and the associated drive setting is
loaded into an internal shadow register and stored.
The bit weighting for temperature inputs represents °C and is compared against the measured data.
Note that the LUT entry does not include a sign bit. The Look Up Table does not support negative
temperature values and the MSBit should not be set for a temperature input.
The bit weighting for voltage inputs represents mV above 0V and is compared against the measured
data.
Each temperature (or voltage) channel threshold shares the same hysteresis value. When the
measured temperature for any of the channels meets or exceeds the programmed threshold, the drive
setting associated with that threshold is used. The temperature must drop below the threshold minus
the hysteresis value before the drive setting will be set to the previous value.
If the RPM based Fan Speed Control Algorithm is used, the TACH Target is updated after every
conversion. It is always set to the minimum TACH Target that is stored by the Look Up Table. The fan
drive setting cycle is updated based on the RPM based Fan Speed Control Algorithm configuration
settings.
If the RPM based Fan Speed Control Algorithm is not used, then the fan drive setting is updated after
every conversion. It is set to the maximum duty cycle that is stored by the Look Up Table.
consecutive thresholds.
TACH /
DRIVE
X
X
X
X
X
X
X
X
Table 6.46 Look Up Table Registers (continued)
752.9
752.9
752.9
B7
-
-
-
-
-
DATASHEET
376.5
376.5
376.5
B6
64
64
64
64
-
69
188.2
188.2
188.2
B5
32
32
32
32
-
94.12
94.12
94.12
B4
16
16
16
16
16
47.06
47.06
47.06
B3
8
8
8
8
8
23.53
23.53
23.53
B2
4
4
4
4
4
Revision 1.74 (05-08-08)
11.76
11.76
11.76
B1
2
2
2
2
2
5.88
5.88
5.88
B0
1
1
1
1
1
DEFAULT
(127°C)
(127°C)
(127°C)
(127°C)
(0.4V)
(0.4V)
(0.4V)
7Fh
7Fh
7Fh
7Fh
7Fh
7Fh
7Fh
0Ah