Datasheet

Data Sheet ADT7420
Rev. 0 | Page 21 of 24
INT AND CT OUTPUTS
The INT and CT pins are open-drain outputs, and both pins
require a 10 kΩ pull-up resistor to V
DD
. The ADT7420 must
be fully powered up to V
DD
before reading INT and CT data.
UNDERTEMPERATURE AND OVERTEMPERATURE
DETECTION
The INT and CT pins have two undertemperature/overtempera-
ture modes: comparator mode and interrupt mode. The interrupt
mode is the default power-up overtemperature mode. The INT
output pin becomes active when the temperature is greater than
the temperature stored in the T
HIGH
setpoint register or less than
the temperature stored in the T
LOW
setpoint register. How this
pin reacts after this event depends on the overtemperature mode
selected.
Figure 18 illustrates the comparator and interrupt modes for
events exceeding the T
HIGH
limit with both pin polarity settings.
Figure 19 illustrates the comparator and interrupt modes for
events exceeding the T
LOW
limit with both pin polarity settings.
Comparator Mode
In comparator mode, the INT pin returns to its inactive status
when the temperature drops below the T
HIGH
− T
HYST
limit or
rises above the T
LOW
+ T
HYST
limit.
Putting the ADT7420 into shutdown mode does not reset the
INT state in comparator mode.
Interrupt Mode
In interrupt mode, the INT pin goes inactive when any ADT7420
register is read. Once the INT pin is reset, it goes active again
only when the temperature is greater than the temperature stored
in the T
HIGH
setpoint register or less than the temperature stored
in the T
LOW
setpoint register.
Placing the ADT7420 into shutdown mode resets the INT pin
in the interrupt mode.
TEMPERATURE
82°C
81°C
80°C
79°C
78°C
77°C
76°C
75°C
74°C
73°C
INT PIN
(COMPARA
TOR MODE)
POLARITY =
ACTIVE LOW
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE LOW
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE HIGH
INT PIN
(COMPARATOR MODE)
POLARITY =
ACTIVE HIGH
T
HIGH
T
HIGH
– T
HYST
TIME
READ
READ READ
09013-020
Figure 18. INT Output Temperature Response Diagram for T
HIGH
Overtemperature Events