High-Side Current-Sense and Internal 1°C Temperature Monitor
Datasheet
4.4
ALERT Output
The ALERT pin is an open drain output and requires a pull-up resistor to VPULLUP 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 (see Section 5.5).
The ALERT pin modes apply to the High Limit only for all channels. The Low Limits will always cause
the ALERT pin to behave as if it were in Interrupt mode.
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 SMBus Alert outputs can be hard-wired
together.
4.4.1
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 temperature measurement and the
consecutive alert queue has been filled.
Additionally, the ALERT pin may be asserted if the measured current or the source voltage are out of
limit (> high limit or < low limit).
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. The pin can be masked by setting the MASK_ALL bit. Once the ALERT pin has been masked,
it will be de-asserted and remain de-asserted until the MASK_ALL bit is cleared by the user. Any
interrupt conditions that occur while the ALERT pin is masked will update the Status Register normally.
When the ALERT pin is configured to operate in Interrupt mode, the Peak Detector circuitry will not
generate interrupts when a current peak is detected.
4.4.2
ALERT Pin Comparator Mode
When the ALERT pin is configured to operate in Comparator mode, it will be asserted if the measured
temperature meets or exceeds the high limit. The ALERT pin will remain asserted until the temperature
drops below the high limit minus the Tcrit Hysteresis value (see Section 5.9).
Additionally, the ALERT pin may be asserted if the measured current or the source voltage meet or
exceed their respective high limit. The ALERT pin will remain asserted until the measured values drop
below the corresponding high limit minus the Vcrit Hysteresis value (see Section 5.23).
When the ALERT pin is asserted in Comparator mode, the corresponding high limit 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_ALL (see Section 5.5) bit will not block the ALERT pin in this mode; however, individual
mask bits (see Section 5.10) will control the respective events that will assert the ALERT pin.
When the ALERT pin is configured to operate in Comparator mode and the Peak Detector circuitry is
linked to the ALERT pin, an interrupt will be generated when a current peak is detected (see
Section 5.15).
4.5
THERM Output
The THERM output is asserted independently of the ALERT output and cannot be masked. Whenever
the measured temperature meets or exceeds the user programmed Tcrit Limit value for the
programmed number of consecutive measurements, the THERM output is asserted. Once it has been
asserted, it will remain asserted until the measured temperatures drops below the Tcrit Limit minus the
Tcrit Hysteresis (also programmable).
Additionally, the THERM pin will be asserted if the current sense Peak Detection circuitry has detected
a current spike (see Section 4.1.4). The THERM pin will remain asserted so long as the Peak Detection
circuitry continues to detect excessive instantaneous current (greater than the programmed threshold).
Revision 1.2 (09-27-10)
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