ADT7475 Analog Devices, Inc., ADT7475 Datasheet - Page 25

• Manufacturer Part Number: ADT7475
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

Configuring the
1.
2.
3.
4.
5.
Configure the relevant pin as the
Setting Bit 1 (
enables the
is disabled on Pin 9 by default.
Setting Bit 0 and Bit 1 (PIN9FUNC) of Configuration
Register 4 (0x7D) enables
tionality on Pin 9 (Bit 1, THERM
Register 3, must also be set). Pin 9 can also be used as
TACH4.
Select the desired fan behavior for
Assuming that the fans are running, setting Bit 2 (BOOST
bit) of Configuration Register 3 (0x78) causes all fans to
run at 100% duty cycle whenever
allows fail-safe system cooling. If this bit is 0, the fans run
at their current settings and are not affected by
events. If the fans are not already running when
asserted, the fans do not run to full speed.
Select whether
SMBALERT
A
Bit 5 (F4P) of Interrupt Mask Register 2 (0x75), when set,
masks out
value is exceeded. This bit should be cleared if
based on
Select a suitable
This value determines whether an
on the first
THERM
A
causes an
assertion.
Select a
This value specifies how often OS- or BIOS-level software
checks the
the
tive
THERM
A
Hour 2, and >2.914 s in Hour 3, this can indicate that system
performance is degrading significantly because
asserting more frequently on an hourly basis.
THERM
A
THERM
A
THERM
A
E
E A
E
E A
assertion time is <22.76 ms in Hour 1, >182.08 ms in
THERM
A
assertion time limit is exceeded. A value of 0x00
SMBALERT
A
SMBALERT
A
THERM
A
THERM
A
THERM
A
E
E A
E
E A
interrupts.
E
E A
timer once an hour to determine the cumula-
assertion time. If, for example, the total
THERM
A
THERM
A
THERM
A
THERM
A
E
E A
E
E A
monitoring time.
events are required.
E
E A
E
E A
timer. For example, BIOS could read
E
E A
assertion or only if a cumulative
timer monitoring functionality. This
E
E A
Behavior
) of Configuration Register 3 (0x78)
E
E A
E
E A
to be generated on the first
s when the
E
E A
E
E A
timer events should generate
E
E A
limit value.
THERM
A
, of Configuration
E
THERM
A
THERM
A
THERM
A
SMBALERT
A
THERM
A
E
E A
timer/output func-
E
E A
E
E A
timer input.
is asserted. This
E
E A
E
E A
timer limit
timer events.
SMBALERT
A
THERM
A
E
E A
THERM
A
is generated
THERM
A
THERM
A
E
E A
is
Rev. B | Page 25 of 68
E
E A
s
E
E A
E
E A
is
E
E A
Configuring the THERM Pin as an Output
In addition to monitoring
can optionally drive
PROCHOT
A
processor by asserting
system-critical thermal limits. If the temperature exceeds a
thermal limit by 0.25°C,
ture is still above the thermal limit on the next monitoring
cycle,
the temperature is equal to or below the thermal limit. Because
the temperature for that channel is measured only once for
every monitoring cycle, after
to remain low for at least one monitoring cycle.
The
local, or Remote 2
0.25°C. The
0x6A, Register 0x6B, and Register 0x6C. Setting Bit 3 of
Register 0x5F, Register 0x60, and Register 0x61 enables the
THERM
A
temperature channels, respectively. Figure 30 shows how the
THERM
A
over temperature.
An alternative method of disabling
THERM
A
or −128°C or less in twos complement mode; that is, for
THERM
A
respectively,
THERM
A
THERM
THERM LIMIT
THERM LIMIT
Alternatively, OS- or BIOS-level software can timestamp
when the system is powered on. If an SMBALERT is gen-
erated due to the
another timestamp can be taken. The difference in time
can be calculated for a fixed
For example, if it takes one week for a
of 2.914 seconds to be exceeded and the next time it takes
only one hour, this is an indication of a serious degradation
in system performance.
THERM
A
Figure 30. Asserting
0.25°C
E
E A
E
E A
E
E A
E
E A
output feature for the Remote 1, local, and Remote 2
pin asserts low as an output in the event of a critical
temperature limit to −64°C or less in Offset 64 mode,
temperature limit values less than −64°C or −128°C,
TEMP
E
E A
THERM
A
is bidirectional,
THERM
A
E
E A
pin can be configured to assert low if the Remote 1,
E
E A
stays low.
THERM
A
THERM
A
E
E A
temperature limit registers are at Register
E
E A
is disabled.
THERM
A
PROCHOT
A
MONITORING
THERM
A
THERM
A
THERM
A
CYCLE
THERM
A
THERM
A
E
E A
temperature limit is exceeded by
THERM
A
E
E A
THERM
A
low as an output. In cases where
E
E A
as an Output, Based on Tripping
E
E A
timer limit being exceeded,
E
E
Limits
THERM
A
E
E A
asserts low. If the tempera-
E
E A
. The user can preprogram
E
E A
remains asserted low until
E
E A
THERM
A
as an input, the ADT7475
E
E A
can be used to throttle the
E
E A
asserts, it is guaranteed
E
E A
timer limit time.
THERM
A
E
E A
is to program the
ADT7475
E
E A
timer limit