ACT8740
Rev PrB, 25-Feb-08
SYSTEM MANAGEMENT
nMSTR Enable Input
In most applications, connect nMSTR to an active
low, momentary push-button switch to utilize the
ACT8740’s closed-loop enable/disable functionality.
If a momentary-on switch is not used, drive nMSTR
to GA or to a logic low to initiate a startup se-
quence.
nIRQ Output
The ACT8740 provides an active-low, open-drain
push-button status output that sinks current when
nMSTR is driven to a logic-low. Connect a pull-up
resistor from nIRQ to an appropriate voltage supply.
nIRQ is typically used to drive the interrupt input of
the system processor, and is useful in a variety of
software-controlled enable/disable control routines.
Thermal Shutdown
The ACT8740 integrates thermal shutdown protec-
tion circuitry to prevent damage resulting from ex-
cessive thermal stress, as may be encountered un-
der fault conditions. This circuitry disables all regu-
lators if the ACT8740 die temperature exceeds
160°C, and prevents the regulators from being en-
abled until the IC temperature drops by 20°C (typ).
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