Datasheet

Data Sheet ADT75
Rev. B | Page 19 of 24
OS/ALERT OUTPUT OVERTEMPERATURE MODES
The ADT75 has two overtemperature modes, comparator mode
and interrupt mode. The OS/ALERT pin defaults on power up
as an OS pin; the comparator mode is the default power up
overtemperature mode. The OS/ALERT output pin becomes
active when the temperature measured exceeds the temperature
limit stored in the T
OS
setpoint register. How this pin reacts after
this event depends on the overtemperature mode selected.
Comparator Mode
In the comparator mode, the OS/ALERT pin returns to its
inactive status when the temperature measured drops below the
limit stored in the T
HYST
setpoint register. Putting the ADT75
into shutdown mode does not reset the OS/ALERT state in
comparator mode.
Interrupt Mode
In the interrupt mode, the OS/ALERT pin goes inactive when
any ADT75 register is read. The OS/ALERT pin can only return
to active status if the temperature measured is below the limit
stored in the T
HYST
setpoint register. Once the OS/ALERT pin is
reset, it goes active again only when the temperature has gone
above the T
OS
limit. The OS/ALERT pin can also be reset by a
SMBus alert response address (ARA) when this pin has been
selected as a SMBus alert pin. More information is given in the
SMBUS Alert section.
Figure 19 illustrates the comparator and interrupt modes with
both pin polarity settings. Placing the ADT75 into shutdown
mode resets the OS/ALERT 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
OS/ALERT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE LOW
OS/ALERT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE LOW
OS/ALERT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE HIGH
OS/ALERT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE HIGH
T
OS
T
HYST
TIME
READ
READ READ
05326-018
Figure 19. OS/ALERT Output Temperature Response Diagram