Datasheet

ADT7408
Rev. 0 | Page 16 of 24
EVENT PIN FUNCTIONALITY
Figure 12 shows the three differently defined outputs of EVENT#
corresponding to the temperature change. EVENT# can be
programmed to be one of the three output modes in the
configuration register.
If while in interrupt mode the temperature reaches the critical
temperature, the device switches to the comparator mode
automatically and asserts the EVENT# output. When the
temperature drops below the critical temperature, the part
switches back to either interrupt mode or comparator mode,
as programmed in the configuration register.
Note that
Figure 12 is drawn with no hysteresis, but the values
programmed into Configuration Register 0x01, Bit[10:9] affect
the operation of the event trigger points. See
Figure 11 for the
explanation of hysteresis functionality.
Event Thresholds
All event thresholds use hysteresis as programmed in the
Configuration Register 0x01, Bit[10:9] to set when they
deassert.
Alarm Window Trip
The device provides a comparison window with an upper
temperature trip point in the alarm upper boundary register
and a lower trip point in the alarm lower boundary register.
When enabled, the EVENT# output is triggered whenever entering
or exiting (crossing above or below) the alarm window.
Critical Trip
The device can be programmed in such a way that the EVENT#
output is triggered only when the temperature exceeds critical
trip point. The critical temperature setting is programmed in
the critical temperature register. When the temperature sensor
reaches the critical temperature value in this register, the device
is automatically placed in comparator mode, meaning that the
critical event output cannot be cleared through software by
setting the clear event bit.
Interrupt Mode
After an event occurs, software can write a 1 to the clear event
bit in the configuration register to de-assert the EVENT#
interrupt output, until the next trigger condition occurs.
Comparator Mode
Reads/writes on the device registers do not affect the EVENT#
output in comparator mode. The EVENT# signal remains
asserted until the temperature drops outside the range or until
the range is reprogrammed such that the current temperature is
outside the range.
ALARM
WINDOW
EVENT# IN “INTERRUPT”
EVENT# IN “COMPARATOR” MODE
EVENT# IN “CRITICAL TEMP ONLY” MODE
CRITICAL
TEMPERATURE
HYSTERESIS AFFECTS
THESE TRIP POINTS
S/W CLEARS EVENT
TIME
05716-007
1. EVENT# CANNOT BE CLEARED ONCE THE DUT TEMPERATURE
IS GREATER THAN THE CRITICAL TEMPERATURE
Figure 12. Temperature, Trip, and Events