Datasheet
TIME
TEMPERATURE
(Active Low)
Measured Temperature
T
HIGH
Limit
T
LOW
Limit
ALERT
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One
Conversion Time
ALERT
TIME
TEMPERATURE
Measured Temperature
T
HIGH
Limit
T
LOW
Limit
ALERT
pin
LM73
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SNIS141D –OCTOBER 2005–REVISED MAY 2009
ALERT FUNCTION
The ALERT output is an over-temperature indicator. At the end of every temperature conversion, the measured
temperature is compared to the value in the T
HIGH
Register. If the measured temperature exceeds the value
stored in T
HIGH
, the ALERT output goes active (see Figure 7). This over-temperature condition will also cause the
ALRT_STAT bit in the Control/Status Register to change value (this bit mirrors the logic level of the ALERT pin).
The ALERT pin and the ALRT_STAT bit are cleared when any of the following occur:
1. The measured temperature falls below the value stored in the T
LOW
Register
2. A "1" is written to the ALERT Reset bit in the Configuration Register
3. The master resets it through an SMBus Alert Response Address (ARA) procedure
If ALERT has been cleared by the master writing a "1" to the ALERT Reset bit, while the measured temperature
still exceeds the T
HIGH
setpoint, ALERT will go active again after the completion of the next temperature
conversion.
Each temperature reading is associated with a Temperature High (THI) and a Temperature Low (TLOW) flag in
the Control/Status Register. A digital comparison determines whether that reading is above the T
HIGH
setpoint or
below the T
LOW
setpoint. If so, the corresponding flag is set. All digital comparisons to the T
HIGH
, and T
LOW
values
are based on an 11-bit temperature comparison. Regardless of the resolution setting of the LM73, the lower
three temperature LSBs will not affect the state of the ALERT output, THI flag, and TLOW flag.
Figure 7. ALERT Temperature Response Cleared when Temperature Crosses T
LOW
Figure 8. ALERT Temperature Response Cleared by Writing a "1" to the ALERT Reset Bit.
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