ASC7512 ETC2 [List of Unclassifed Manufacturers], ASC7512 Datasheet - Page 19

• Manufacturer Part Number: ASC7512
• Description: DIGITAL TEMPERATURE SENSOR WITH INTEGRATED FAN CONTROL
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Automatic Fan Control
Auto Fan Control Operating Mode
The aSC7512 includes the circuitry for automatic fan control. In Auto Fan Mode, the aSC7512 will automatically adjust the
PWM duty cycle of the PWM output. PWM outputs are assigned to a thermal zone based on the fan configuration registers.
At any time, the temperature of a zone exceeds its absolute limit, all PWM outputs will go to 100% duty cycle to provide
maximum cooling to the system.
Example for PWM1 assigned to Zone 1:
In this case, the PWM duty cycle will be 50% at 50°C.
Since (Zone 1 Fan Temp Limit) + (Zone 1 Range) = 50°C + 8°C = 58°C, the fan will run at 100% duty cycle when the
temperature of the Zone 1 sensor reaches 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 Fan Temp Limit) + (Zone 1 Range), the duty cycle will be 100%.
© Andigilog, Inc. 2006
•
•
•
PWM %
PWM %
Zone 1 Fan Temp Limit (Register 67h) is set to 50°C (32h).
Zone 1 Range (Register 5Fh) is set to 8°C (6xh).
Fan PWM Minimum (Register 64h) is set to 50% (32h).
100%
100%
0%
0%
Example
Example
Temperature
Temperature
PWM Set to Off
PWM Set to Off
Minimum PWM set to 50%, fan speed increases linearly beyond 50 °C but will not return to
Minimum PWM set to 50%, fan speed increases linearly beyond 50 °C but will not return to
User Choice: Set to
User Choice: Set to
PWM set to Off or
PWM set to Off or
this Temperature
this Temperature
Fan Temp Limit
Fan Temp Limit
Minimum Below
Minimum Below
less Hysteresis
less Hysteresis
Temperature °C
Temperature °C
(0 °C to 15 °C)
(0 °C to 15 °C)
Minimum or Off
Minimum or Off
Hysteresis
Hysteresis
off until it has gone below Fan Temp Limit by the 5 °C Hysteresis setting to 45°C.
off until it has gone below Fan Temp Limit by the 5 °C Hysteresis setting to 45°C.
PWM %
PWM %
PWM Set to
PWM Set to
Minimum
Minimum
Figure 8 Automatic Fan Speed Control Example
Min%
Min%
Hysteresis
Hysteresis
Off/
Off/
45
45
5 °C
5 °C
50
50
Min%
Min%
Fan Temp
Fan Temp
www.andigilog.com
Linear Control Range
Linear Control Range
Limit
Limit
(2 °C to 80 °C)
(2 °C to 80 °C)
- 19 -
Range
Range
Range
Range
8 °C
8 °C
100%
100%
58
58
Fan Temp Limit
Fan Temp Limit
PWM 100%
PWM 100%
plus Range
plus Range
August 2006 - 70A05003
80
80
aSC7512
Absolute
Absolute
Limit
Limit