Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
B.2
Example #2
This example uses the RPM based Fan Speed Control Algorithm. The Spin Level (used by the Spin
Up Routine) should be changed to 50% drive for a total Spin Time of 1 second. For all other RPM
configuration settings, the default conditions are used.
For control inputs, it uses the External Diode 1 channel normally, a thermistor input on the External
Diode 2 channel, the internal diode channel, and a Pushed Temperature that represents the MCU
temperature in standard format. The configuration is set as shown in Table B.5 while Table B.6 shows
how the table is loaded.
Note that when using Thermistor data, the VIN2_INV bit should be set. The circuitry will automatically
subtract the measured thermistor voltage from a quantity of FFh (effectively inverting it). Therefore, the
Look Up Table is loaded with ascending voltage thresholds with respect to the drive settings.
Additionally, the reading register will show this same value (subtracted from FFh).
Table B.5 Look Up Table Example #2 Configuration
ADDR
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
SETTING
Configuration
3
-
VIN4_I
NV
VIN3_E
N
VIN3_I
NV
VIN2_
EN
VIN2_I VIN1_
VIN1_I
NV
NV
EN
0
22h
42h
46h
50h
0Ch
-
0
0
0
1
1
0
EN_
ALGO
Fan 1
Configuration
1
RANGE[1:0]
EDGES[1:0]
UPDATE[2:0]
1
CBh
0Ah
28h
1
1
0
0
1
0
0
1
DRIVE_FAIL_CNT
1 [1:0]
NOKICK
1
SPINUP_TIME
[1:0]
Fan 1 Spin
Up
Configuration
SPIN_LVL[2:0]
1
0
0
0
0
1
0
USE_D
TS_F1
USE_D LUT_LO
TS_F2
TACH /
DRIVE
TEMP3_CFG
[1:0]
TEMP4_CFG
[1:0]
LUT 1
Configuration
CK
0
0
1
0
1
0
0
0
Table B.6 Fan Speed Control Table Example #2
FAN
SPEED
STEP #
EXTERNALDIODE
1 TEMPERATURE
(CPU)
THERMISTOR 2
VOLTAGE
PUSHED
TEMPERATURE
SETTING
INTERNAL DIODE
TEMPERATURE
(AMBIENT)
TACH
TARGET
READING
156.25mV
(45°C)
3Dh
(1007 RPM)
1
2
3
4
5
35oC
40oC
50oC
60oC
70oC
30oC
35oC
40oC
45oC
50oC
40oC
45oC
50oC
55oC
60oC
178.125mV
(50°C)
1Eh
(2048 RPM)
203.125mV
(55°C)
14h
(3072 RPM)
228.125mV
(60°C)
0Fh
(4096 RPM)
253.125mV
(65°C)
0Ch
(5120 RPM)
SMSC EMC2104
Revision 1.74 (05-08-08)
DATA9S3HEET
SMSC [ SMSC CORPORATION ]
