Step 9: Operating Points For Temperature Channels - Analog Devices ADT7473 Manual

STEP 9: OPERATING POINTS FOR TEMPERATURE
CHANNELS
The operating point for each temperature channel is the optimal
temperature for that thermal zone. The hotter each zone is
allowed to be, the quieter the system, because the fans are not
required to run as fast. The ADT7473 increases or decreases fan
speeds as necessary to maintain the operating point tempera-
ture, allowing for system-to-system variation and removing the
need for worst-case design. If a sensible operating point value is
chosen, any T value can be selected in the system charac-
MIN
terization. If the T value is too low, the fans run sooner than
MIN
required, and the temperature is below the operating point. In
response, the ADT7473 increases T
longer and to allow the temperature zone to get closer to the
operating point. Likewise, too high a T
operating point to be exceeded, and in turn, the ADT7473
reduces T to turn the fans on sooner to cool the system.
MIN
REMOTE 2 =
CPU TEMP
LOCAL =
VRM TEMP
REMOTE 1 =
AMBIENT TEMP
to keep the fans off
MIN
value causes the
MIN
THERMAL CALIBRATION
100%
0%
T T
MIN RANGE
THERMAL CALIBRATION
100%
MUX
0%
T T
MIN RANGE
THERMAL CALIBRATION
100%
0%
T T
MIN RANGE
Figure 64. Operating Point Value Dynamically Adjusts Automatic Fan Control Settings
Rev. 0 | Page 47 of 76
Programming Operating Point Registers
There are three operating point registers, one for each
temperature channel. These 8-bit registers allow the operating
point temperatures to be programmed with 1°C resolution.
Operating Point Registers
Reg. 0x33, Remote 1 Operating Point = 0xA4 (100°C default)
Reg. 0x34, Local Operating Point = 0xA4 (100°C default)
Reg. 0x35, Remote 2 Operating Point = 0xA4 (100°C default)
PWM
MIN
OPERATING
RAMP
POINT
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 2
MEASUREMENT
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 3
AND 4
MEASUREMENT
PWM
CONFIG
PWM
PWM1
GENERATOR
TACH1
PWM
CPU FAN SINK
CONFIG
PWM
PWM2
GENERATOR
TACH2
PWM
CONFIG
FRONT CHASSIS
PWM
PWM3
GENERATOR
TACH3
REAR CHASSIS
ADT7473