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

1. EVENT# CANNOT BE CLEARED ONCE THE DUT TEMPERATURE

IS GREATER THAN THE CRITICAL TEMPERATURE

Figure 12. Temperature, Trip, and Events