LP3910SQ-AN Datasheet, PDF (43/60 Pages) National Semiconductor (TI) – Power Management IC for Hard Drive Based Portable Media Players

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Interrupt Request Output
The LP3910SQ-AN has the ability to interrupt the system pro-
cessor through the open drain IRQB pin, which transitions to
an active logic low level upon the following 8 events:
• USB Power detected
• USB disconnected
• CHG_IN Power detected
• CHG_IN Disconnected
• Battery low alarm
• Thermal Alarm
• ADC conversion completed
• Charger safety timer time-out
The events form the interrupt sources that correspond to a
certain bit location in the Interrupt Request (IRQ) Register. All
interrupt sources can be masked by the Interrupt Mask Reg-
ister (IMR). Masking the interrupt prevents the interrupt event
from asserting the IRQB pin, yet the event will still be captured
in the IRQ register, which allows the processor to poll the in-
terrupt sources.
After an active low IRQB has been detected by the system
processor, the latter services the interrupt and will access the
IRQ register to determine which source was responsible for
the interrupt request. Reading the IRQ register will automati-
cally clear the register to enable the capture of the next
interrupt events.
As new interrupts can occur while the I²C read cycle is clear-
ing the IRQ register, a buffer register called Interrupt Pending
Register (IPR), not accessible through the I²C compatible in-
terface holds the next interrupts. De-asserting the IRQB out-
put is immediately followed by a new transition of IRQB to
logic low when an interrupt is pending.
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