Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
Table B.6 Fan Speed Control Table Example #2 (continued)
FAN
SPEED
STEP #
EXTERNALDIODE
1 TEMPERATURE
(CPU)
THERMISTOR 2
VOLTAGE
PUSHED
TEMPERATURE
SETTING
INTERNAL DIODE
TEMPERATURE
(AMBIENT)
TACH
TARGET
READING
278.125mV
(70°C)
0Ah
(6144 RPM)
6
7
8
80oC
90oC
55oC
60oC
65oC
65oC
70oC
75oC
306.25mV
(75°C)
09h
(6826 RPM)
334.375mV
(80°C)
08h
(7680 RPM)
100oC
Note: The values shown in Table B.6 are example settings. All the cells in the look-up table are
programmable via SMBus.
Table B.7 Fan Speed Determination for Example #2 (using settings in Table B.6)
EXTERNAL
DIODE 1
TEMPERATURE
(CPU)
THERMISTOR 2
VOLTAGE
INTERNAL DIODE
TEMPERATURE
(AMBIENT)
PUSHED
TEMPERATURE
FAN DRIVE
SETTING RESULT
READING
0Ch (5120RPM) -
CPU requires highest
target
Example 1:
Example 2:
75°C
140.375mV
48°C
58°C
58°C
58°C
09h (6826 RPM)
Thermistor requires
highest target
75°C
310mV
09h (6826 RPM)
Pushed Temperature
requires highest
target
Example 3:
75°C
235.125mV
58°C
62°C
Revision 1.74 (05-08-08)
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