EMC1428 datasheet(16/53 Pages) MICROCHIP

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1°C Multiple Temperature Sensor with HW Thermal Shutdown & Hottest of Thermal Zones

Data Sheet

DS20005275A-page 16

 2014 Microchip Technology Inc.

4.1

ALERT Output

The ALERT pin is an open drain output and has two modes of operation: interrupt mode and

comparator Mode. The mode of the ALERT output is selected via the ALERT / COMP bit in the

Configuration Register.

4.1.1

ALERT Pin Interrupt Mode

When configured to operate in interrupt mode, the ALERT pin asserts low when an out of limit

measurement (> high limit or < low limit) is detected on any diode or when a diode fault is detected.

The ALERT pin will remain asserted as long as an out-of-limit condition remains. Once the out-of-limit

condition has been removed, the ALERT pin will remain asserted until the appropriate status bits are

cleared. Each channel is subject to the fault queue (see Section 5.14).

The ALERT pin can be masked by setting the MASK bit. Once the ALERT pin has been masked, it

will be de-asserted and remain de-asserted until the MASK bit is cleared by the user. Any interrupt

conditions that occur while the ALERT pin is masked will update the Status Register normally.

The ALERT pin is used as an interrupt signal or as an SMBus Alert signal that allows an SMBus slave

to communicate an error condition to the master. One or more ALERT outputs can be hard-wired

together.

4.1.2

ALERT Pin Comparator Mode

When the ALERT pin is configured to operate in comparator mode it will be asserted if any of the

measured temperatures meets or exceeds the respective high limit or drops below the respective low

limit. The ALERT pin will remain asserted until all temperatures drop below the corresponding high

limit minus the THERM Hysteresis value.

When the ALERT pin is asserted in comparator mode, the corresponding status bits will be set.

Reading these bits will not clear them until the ALERT pin is deasserted. Once the ALERT pin is

deasserted, the status bits will be automatically cleared.

The MASK bit will not block the ALERT pin in this mode, however the individual channel masks (see

Section 5.13) will prevent the respective channel from asserting the ALERT pin. In addition, each

channel is subject to the fault queue (see Section 5.14).

4.2

SYS_SHDN Output

The SYS_SHDN output is asserted independently of the ALERT output and cannot be masked. If the

External Diode 1 temperature exceeds the Hardware Critical / Thermal Shutdown Limit for the

programmed number of consecutive measurements, then the SYS_SHDN pin is asserted.

The Hardware Critical / Thermal Shutdown Limit is defined by the TRIP_SET pin as described in

Section 4.3.

In addition to External Diode 1 channel triggering the SYS_SHDN pin when the measured temperature

exceeds to the Hardware Critical / Thermal Shutdown Limit, each of the temperature measurement

channels can be configured to assert the SYS_SHDN pin when they exceed the corresponding

THERM Limit.

When the SYS_SHDN pin is asserted, it will not release until the External Diode 1 temperature drops

below the Hardware Thermal Shutdown Limit minus 10°C and all other measured temperatures drop

below the THERM Limit minus the THERM Hysteresis value (when linked to SYS_SHDN).

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