EMC6D103S_07 Datasheet, PDF (64/84 Pages) SMSC Corporation – Fan Control Device with High Frequency PWM Support and Hardware Monitoring Features

8.2.15
Fan Control Device with High Frequency PWM Support and Hardware Monitoring Features
Datasheet
Registers 5F-61h: Zone Temperature Range, PWM Frequency
Table 8.26 Registers 5F-61h: Zone Temperature Range, PWM Frequency
Register
Address
5Fh
Read/
Write
R/W
60h
R/W
61h
R/W
Register Name
Zone 1 Range / Fan 1
Frequency
Zone 2 Range / Fan 2
Frequency
Zone 3 Range / Fan 3
Frequency
Bit 7
(MSb)
RAN3
Bit 6
RAN2
Bit 5
RAN1
Bit 4
RAN0
Bit 3
FRQ3
Bit 2
FRQ2
Bit 1
FRQ1
Bit 0
(LSb)
FRQ0
Default
Value
C3h
RAN3 RAN2 RAN1 RAN0 FRQ3 FRQ2 FRQ1 FRQ0
C3h
RAN3 RAN2 RAN1 RAN0 FRQ3 FRQ2 FRQ1 FRQ0
C3h
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
In Auto Fan Mode, when the temperature for a zone is above the Low Temperature Limit (registers
67-69h) and below the Absolute Temperature Limit (registers 6A-6Ch) the speed of a fan assigned to
that zone is determined as follows by the auto fan control logic.
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.
Below Fan Temp Limit: Fan at Fan PWM
Minimum
PWM Duty is linear
this range
Temperature
Temperature Low LIMIT:
output at MIN FAN
Low LIMIT+ RANGE:
Output at 100% Duty
Figure 8.1 Fan Activity Above Low Temp Limit
Example for PWM1 assigned to Zone 1:
„ 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)
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%.
Revision 0.2 (09-25-07)
64
DATASHEET
SMSC EMC6D103S