ADT75 datasheet(20/25 Pages) AD

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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 TOS 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 THYST 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 THYST setpoint register. Once the OS/ALERT pin is

reset, it goes active again only when the temperature has gone

above the TOS 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

TOS

THYST

TIME

READ

Figure 19. OS/ALERT Output Temperature Response Diagram

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