EMC6D102 SMSC Corporation, EMC6D102 Datasheet - Page 61

• Manufacturer Part Number: EMC6D102
• Description: Fan Control Device
• Manufacturer: SMSC Corporation

Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102
Temperature
Below Fan Temp Limit: Fan is off or at Fan PWM
Minimum depending on bit[7:5] of register 62h
When the temperature reaches the temperature value programmed in the Zone x Low Temp Limit
register, the PWM output assigned to that zone is at PWMx Minimum Duty Cycle. Between Zone x
Low Temp Limit and (Zone x Low Temp Limit + Zone x Range), the PWM duty cycle increases linearly
according to the temperature as shown in the figure below.
Example for PWM1 assigned to Zone 1:
In this case, the PWM1 duty cycle will be 50% at 50°C.
Since (Zone 1 Low Temp Limit) + (Zone 1 Range) = 50°C + 8°C = 58°C, the fan controlled by PWM1
will run at 100% duty cycle when the temperature of the Zone 1 sensor is at 58°C.
Since the midpoint of the fan control range is 54°C, and the median duty cycle is 75% (Halfway
between the PWM Minimum and 100%), PWM1 duty cycle would be 75% at 54°C.
Above (Zone 1 Low Temp Limit) + (Zone 1 Range), the duty cycle must be 100%.
The PWM frequency bits [2:0] determine the PWM frequency for the fan.
PWM Frequency Selection (Default =011=29.3Hz)
Range Selection (Default =1100=32×C)
Zone 1 Low Temp Limit (Register 67h) is set to 50°C (32h).
Zone 1 Range (Register 5Fh) is set to 8°C (7h)
PWM1 Minimum Duty Cycle (Register 64h) is set to 50% (80h)
and bit 2 of register 7Fh
FREQ[2:0]
Figure 7.11 Fan Activity Above Fan Temp Limit
Table 7.9 Register Setting vs. PWM Frequency
000
001
010
100
101
011
110
111
output at MIN FAN SPEED
Temperature LIMIT: PWM
DATASHEET
61
PWM FREQUENCY
11.0 Hz
14.6 Hz
21.9 Hz
29.3 Hz
35.2 Hz
44.0 Hz
58.6 Hz
87.7 Hz
PWM Duty is linear over
this range
LIMIT+ RANGE: PWM
Output at 100% Duty
Revision 0.4 (06-15-06)