ADT7468 Datasheet, PDF (52/81 Pages) Analog Devices – dBCool™ Remote Thermal Controller and Voltage Monitor

ADT7468
100%
T_RANGE
0%
T_MIN
T _THERM
THERMAL CALIBRATION
100%
T_MIN
0%
T_RANGE
THERMAL CALIBRATION
REMOTE 2 =
100%
CPU TEMP
MUX
LOCAL =
VRM TEMP
T_MIN
0%
T_RANGE
THERMAL CALIBRATION
100%
REMOTE 1 =
AMBIENT TEMP
T_MIN
0%
T_RANGE
PWM
MIN
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
PWM
MIN
TACHOMETER 1
MEASUREMENT
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
PWM
MIN
TACHOMETER 2
MEASUREMENT
RAMP
CONTROL
(ACOUSTIC
ENHANCEMENT)
TACHOMETER 3
AND 4
MEASUREMENT
PWM
CONFIG
PWM
GENERATOR
PWM
CONFIG
PWM
GENERATOR
PWM
CONFIG
PWM
GENERATOR
PWM1
TACH1
CPU FAN SINK
PWM2
TACH2
FRONT CHASSIS
PWM3
TACH3
REAR CHASSIS
Figure 69. The THYST Value Applies to Fan On/Off Hysteresis and THERM Hysteresis
Enhance Acoustics Register 1 (Reg. 0x62)
Bit 7 (MIN3) = 0, PWM3 is off (0% PWM duty cycle) when the
temperature is below TMIN − THYST.
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum duty cycle
below TMIN − THYST.
Bit 6 (MIN2) = 0, PWM2 is off (0% PWM duty cycle) when the
temperature is below TMIN − THYST.
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minimum duty cycle
below TMIN − THYST.
Bit 5 (MIN1) = 0, PWM1 is off (0% PWM duty cycle) when the
temperature is below TMIN − THYST.
Bit 5 (MIN1) = 1, PWM1 runs at PWM1 minimum duty cycle
below TMIN − THYST.
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 ADT7468 increases or
decreases fan speeds as necessary to maintain the operating
point temperature, allowing for system-to-system variation and
removing the need for worst-case design. If a sensible operating
point value is chosen, any TMIN value can be selected in the
system characterization. If the TMIN value is too low, the fans run
sooner than required, and the temperature is below the operat-
ing point. In response, the ADT7468 increases TMIN to keep the
fans off longer and to allow the temperature zone to get closer
to the operating point. Likewise, too high a TMIN value causes
the operating point to be exceeded, and in turn, the ADT7468
reduces TMIN to turn the fans on sooner to cool the system.
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)
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