ADT7468 Analog Devices, Inc., ADT7468 Datasheet - Page 56

• Manufacturer Part Number: ADT7468
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7468
Figure 75 shows how T
ture is above T
T
operating point. Once the temperature rises above the low
temperature limit, T
Preventing T
Because T
to reach full scale (127°C), because the fan would never switch
on. As a result, T
range:
1.
2.
3.
STEP 11: MONITORING THERM
Using the operating point limit ensures that the dynamic T
control mode is operating in the best possible acoustic position
while ensuring that the temperature never exceeds the
maximum operating temperature. Using the operating point
limit allows T
because of its self-corrective nature. In PC design, the
operating point for the chassis is usually the worst-case
internal chassis temperature.
OPERATING
OPERATING
HIGH TEMP
LOW TEMP
HIGH TEMP
LOW TEMP
MIN
THERM
THERM
Figure 76. T
POINT
The lowest possible value for T
complement mode) or −64°C (Offset 64 mode).
T
If the temperature is below T
is running at minimum speed, and dynamic T
disabled.
is below the high temperature limit and below the
POINT
LIMIT
LIMIT
LIMIT
LIMIT
LIMIT
LIMIT
T
MIN
T
MIN
MIN
cannot exceed the high temperature limit.
MIN
HYSTERESIS
Figure 75. Increasing T
HYSTERESIS
is dynamically adjusted, it is undesirable for T
MIN
MIN
ACTUAL
MIN
ACTUAL
MIN
TEMP
TEMP
Adjustments Limited by the High Temperature Limit
MIN
to be independent of system level issues
from Reaching Full Scale
and below the low temperature limit, and
MIN
is allowed to vary only within a specified
MIN
stays the same.
increases when the current tempera-
MIN
MIN
for Quieter Operation
MIN
, the fan is switched off or
T
FROM INCREASING
is –127°C (twos
MIN
PREVENTED
MIN
control is
MIN
MIN
Rev. A | Page 56 of 84
The optimal operating point for the processor is determined by
monitoring the thermal monitor in the Intel Pentium 4 proces-
sor. To do this, the PROCHOT output of the Pentium 4 is
connected to the THERM input of the ADT7468.
The operating point for the processor can be determined by
allowing the current temperature to be copied to the operating
point register when the PROCHOT output pulls the THERM
input low on the ADT7468. This gives the maximum
temperature at which the Pentium 4 can run before clock
modulation occurs.
Enabling the THERM Trip Point as the Operating Point
Bits <4:2> of dynamic T
enable/disable THERM monitoring to program the operating
point.
Dynamic T
<2> PHTR2 = 1, copies the Remote 2 current temperature to
the Remote 2 operating point register, if THERM is asserted.
The operating point contains the temperature at which THERM
is asserted. This allows the system to run as quietly as possible
without affecting system performance.
PHTR2 = 0, ignores any THERM assertions. The Remote 2
operating point register reflects its programmed value.
<3> PHTL = 1, copies the local current temperature to the local
temperature operating point register, if THERM is asserted. The
operating point contains the temperature at which THERM is
asserted. This allows the system to run as quietly as possible
without affecting system performance.
PHTL = 0, ignores any THERM assertions. The local
temperature operating point register reflects its programmed
value.
<4> PHTR1 = 1, copies the Remote 1 current temperature to
the Remote 1 operating point register, if THERM is asserted.
The operating point contains the temperature at which THERM
is asserted. This allows the system to run as quietly as possible
without affecting system performance.
PHTR1 = 0, ignores any THERM assertions. The Remote 1
operating point register reflects its programmed value.
Enabling Dynamic T
Bits <7:5> of dynamic T
enable/disable dynamic T
channels.
Dynamic
<5> R2T = 1, enables dynamic T
temperature channel. The chosen T
adjusted based on the current temperature, operating point, and
high and low limits for this zone.
TMIN
MIN
Control Register 1 (0x36)
Control Register 1 (0x36)
MIN
MIN
MIN
MIN
Control Mode
control Register 1 (Reg. 0x36)
control Register 1 (Reg. 0x36)
control on the temperature
MIN
MIN
control on the Remote 2
value is dynamically