ADT7476 Analog Devices, Inc., ADT7476 Datasheet - Page 44

• Manufacturer Part Number: ADT7476
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7476
STEP 4: PWM
PWM
the system runs. It is also the start speed for each fan under
automatic fan control once the temperature rises above T
For maximum system acoustic benefit, PWM
low as possible. Depending on the fan used, the PWM
ting is usually in the 20% to 33% duty cycle range. This value
can be found through fan validation.
MIN
Figure 54. PWM
PWM
is the minimum PWM duty cycle at which each fan in
100%
MIN
0%
MIN
FOR EACH PWM (FAN) OUTPUT
MIN
AMBIENT TEMP
T
MIN
Determines Minimum PWM Duty Cycle
REMOTE 2 =
REMOTE 1 =
VRM TEMP
CPU TEMP
LOCAL =
100%
0%
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
TEMPERATURE
T
T
T
T
MIN
MIN
MIN
MIN
MIN
T
T
T
RANGE
RANGE
RANGE
should be as
Figure 53. Understanding the T
100%
100%
100%
0%
0%
0%
MIN
MIN
set-
MUX
.
Rev. B | Page 44 of 72
PWM
PWM
PWM
MIN
MIN
MIN
CONFIG
CONFIG
CONFIG
More than one PWM output can be controlled from a single
temperature measurement channel. For example, Remote 1
Temperature can control PWM1 and PWM2 outputs. If two
different fans are used on PWM1 and PWM2, the fan charac-
teristics can be set up differently. As a result, Fan 1 driven by
PWM1 can have a different PWM
connected to PWM2. Figure 55 illustrates this as follows:
PWM1
20%, while PWM2
duty cycle. Note that both fans turn on at exactly the same
temperature, defined by T
Figure 55. Operating Two Different Fans from a Single Temperature Channel
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
MIN
AND 4
PWM
PWM
PWM
Parameter
MIN
PWM2
PWM1
(front fan) is turned on at a minimum duty cycle of
100%
MIN
MIN
0%
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
MIN
(rear fan) turns on at a minimum of 40%
T
MIN
MIN
.
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
FRONT CHASSIS
MIN
REAR CHASSIS
CPU FAN SINK
TEMPERATURE
value than that of Fan 2