ADT7463ARQZ-R7 datasheet(24/52 Pages) ONSEMI

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REV. C

–24–

ADT7463

7 6 54 3 2 1 0

22.76ms

45.52ms

THERM

91.04ms

182.08ms

364.16ms

728.32ms

1.457s

2.914s

OUT

RESET

LATCH

STATUS REGISTER 2

CLEARED

ON READ

F4P BIT (BIT 5)

MASK REGISTER 2

(REG. 0x75)

1 = MASK

SMBALERT

F4P BIT (BIT 5)

THERM TIMER CLEARED ON READ

COMPARATOR

THERM

TIMER

(REG. 0x79)

22.76ms

45.52ms

91.04ms

182.08ms

364.16ms

728.32ms

1.457s

2.914s

THERM LIMIT

(REG. 0x7A)

Figure 27. Functional Diagram of ADT7463’s THERM Monitoring Circuitry

Configuring the Desired THERM Behavior

1. Configure the desired pin as the THERM input.

Setting Bit 1 (THERM Enable) of Configuration Register 3

(Reg. 0x78) enables the THERM monitoring functionality.

This is enabled on Pin 14 by default.

Setting Bit 1 (TH5V) of Configuration Register 4

(Reg. 0x7D) enables THERM monitoring on Pin 20

(Bit 1 of Configuration Register 3 must also be set). Pin 14

can be used as TACH4.

2. Select the desired fan behavior for THERM events.

Setting Bit 2 (BOOST bit) of Configuration Register 3

(Reg. 0x78) causes all fans to run at 100% duty cycle

whenever THERM gets asserted. This allows fail-safe system

cooling. If this bit = 0, the fans run at their current settings

and are not affected by THERM events.

3. Select whether THERM events should generate

SMBALERT interrupts.

Bit 5 (F4P) of Mask Register 2 (Reg. 0x75), when set, masks

out SMBALERTs when the THERM limit value gets

exceeded. This bit should be cleared if SMBALERTs based

on THERM events are required.

4. Select a suitable THERM limit value.

This value determines whether an SMBALERT is generated

on the first THERM assertion, or only if a cumulative THERM

assertion time limit is exceeded. A value of 0x00 causes an

SMBALERT to be generated on the first THERM assertion.

5. Select a THERM monitoring time.

This is how often OS or BIOS level software checks the

THERM timer. For example, BIOS could read the THERM

timer once an hour to determine the cumulative THERM

assertion time. If, for example, the total THERM assertion

time is <22.76 ms in Hour 1, >182.08 ms in Hour 2, and

>5.825 s in Hour 3, this can indicate that system performance

is degrading significantly since THERM is asserting more

frequently on an hourly basis.

Alternatively, OS or BIOS level software can time-stamp

when the system is powered on. If an SMBALERT is gener-

ated due to the THERM limit being exceeded, another

time-stamp can be taken. The difference in time can be

calculated for a fixed THERM limit time. For example, if it

takes one week for a THERM limit of 2.914 s to be exceeded

and the next time it takes only 1 hour, then this is an

indication of a serious degradation in system performance.

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