ADT7463 データシートの表示（PDF） - ON Semiconductor
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ADT7463 Datasheet PDF : 52 Pages
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ADT7463
INT
LOW LIMIT
TEMP =
LOW LIMIT
Figure 18. Temperature = Low Limit: INT Occurs
NO INT
HIGH LIMIT
21.00C
TEMP =
HIGH LIMIT
Figure 19. Temperature = High Limit: No INT
INT
HIGH LIMIT
TEMP >
HIGH LIMIT
Figure 20. Temperature > High Limit: INT Occurs
Analog Monitoring Cycle Time
The analog monitoring cycle begins when a 1 is written to the
start bit (Bit 0) of Configuration Register 1 (Reg. 0x40). The ADC
measures each analog input in turn and as each measurement is
completed, the result is automatically stored in the appropriate
value register. This round-robin monitoring cycle continues
unless disabled by writing a 0 to Bit 0 of Configuration Register 1.
Because the ADC is normally left to free-run in this manner, the
time taken to monitor all the analog inputs is normally not of
interest, since the most recently measured value of any input
can be read out at any time.
For applications where the monitoring cycle time is important,
it is easily calculated.
The total number of channels measured is:
• Four dedicated supply voltage inputs
• 3.3 VSTBY or 5 V supply (VCC pin)
• Local temperature
• Two remote temperatures
As mentioned previously, the ADC performs round-robin
conversions and takes 11.38 ms for each voltage measurement,
12 ms for a local temperature reading, and 25.5 ms for each remote
temperature reading.
The total monitoring cycle time for averaged voltage and tempera-
ture monitoring is therefore nominally
(5 × 11.38) + 12 + (2 × 25.5) = 120 ms
Fan TACH measurements are made in parallel and are not
synchronized with the analog measurements in any way.
Status Registers
The results of limit comparisons are stored in Status Registers 1
and 2. The status register bit for each channel reflects the status
of the last measurement and limit comparison on that channel.
If a measurement is within limits, the corresponding status register
bit is cleared to 0. If the measurement is out-of-limits, the corre-
sponding status register bit is set to 1.
The state of the various measurement channels may be polled
by reading the status registers over the serial bus. In Bit 7 (OOL)
of Status Register 1 (Reg. 0x41), 1 means that an out-of-limit
event has been flagged in Status Register 2. This means that a
user need only read Status Register 2 when this bit is set. Alter-
natively, Pin 10 or Pin 22 can be configured as an SMBALERT
output. This automatically notifies the system supervisor of an
out-of-limit condition. Reading the status registers clears the
appropriate status bit as long as the error condition that caused
the interrupt has cleared. Status register bits are “sticky.” When-
ever a status bit gets set, indicating an out-of-limit condition,
it remains set even if the event that caused it has gone away
(until read). The only way to clear the status bit is to read the
status register after the event has gone away. Interrupt status
mask registers (Reg. 0x74, 0x75) allow individual interrupt
sources to be masked from causing an SMBALERT. However,
if one of these masked interrupt sources goes out-of-limit, its
associated status bit gets set in the interrupt status registers.
Rev. 4 | Page 20 of 52 | www.onsemi.com
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REV. C
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