RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
Table 7.52 Look Up Table Registers (continued)
RPM /
PWM
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
LUT Temp 1
Setting 1
7Fh
(127°C)
52h
R/W
X
-
64
32
16
8
4
2
1
LUT Temp 2
Setting 1
7Fh
(127°C)
53h
54h
R/W
R/W
X
X
X
-
-
-
64
64
64
32
32
32
16
16
16
8
8
8
4
4
4
2
2
2
1
1
1
LUT Temp 3
Setting 1
7Fh
(127°C)
LUT Temp 4
Setting 1
7Fh
(127°C)
55h
. . .
R/W
. . .
. . .
. . .
‘0’
. . .
4096
128
. . .
2048
64
. . .
1024
32
. . .
512
16
. . .
256
8
. . .
128
4
. . .
64
2
. . .
32
1
. . .
LUT Drive
Setting 8
74h
R/W
92h
‘1’
LUT Temp
1Setting 8
7Fh
(127°C)
75h
76h
77h
78h
79h
7Ah
7Bh
7Ch
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
-
-
-
-
-
-
-
-
64
64
64
64
-
32
32
32
32
-
16
16
16
16
16
16
16
16
8
8
8
8
8
8
8
8
4
4
4
4
4
4
4
4
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
LUT Temp 2
Setting 8
7Fh
(127°C)
LUT Temp 3
Setting 8
7Fh
(127°C)
LUT Temp 4
Setting 8
7Fh
(127°C)
LUT Temp 1
Hysteresis
0Ah
(10°C)
LUT Temp 2
Hysteresis
0Ah
(10°C)
-
-
LUT Temp 3
Hysteresis
0Ah
(10°C)
-
-
LUT Temp 4
Hysteresis
0Ah
(10°C)
-
-
The Look Up Table Registers hold the 40 entries of the Look Up Table that control the drive of the
PWM. As the temperature 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.
APPLICATION NOTE: When the PWM Input Duty cycle values are used, then the bit weighting represents a unit-
less threshold that does not corresponded to specific temperature values. It is used to drive
the fan speed based on external temperatures known to a separate microcontroller driving
the PWM_IN pin.
Each temperature channel threshold for a single “column” shares the same hysteresis value; however,
each temperature input has a different 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.
SMSC EMC2113
Revision 1.2 (10-08-09)
DATA6S9HEET
SMSC [ SMSC CORPORATION ]
