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Input
Selects input pin characteristics
Selects 5% or 10% V
CC
detect
Ground
Reset (Active High)
Reset (Active Low, open drain)
Non鈥揗askable Interrupt
+5V Supply
No Connections
DESCRIPTION
The DS1231 Power Monitor Chip uses a precise tem-
perature-compensated reference circuit which provides
an orderly shutdown and an automatic restart of a pro-
cessor-based system. A signal warning of an impending
power failure is generated well before regulated DC
voltages go out of specification by monitoring high volt-
age inputs to the power supply regulators. If line isola-
tion is required a UL-approved opto-isolator can be di-
rectly interfaced to the DS1231. The time for processor
shutdown is directly proportional to the available
hold-up time of the power supply. Just before the
hold-up time is exhausted, the Power Monitor uncondi-
tionally halts the processor to prevent spurious cycles
by enabling Reset as V
CC
falls below a selectable 5 or
10 percent threshold. When power returns, the proces-
sor is held inactive until well after power conditions have
stabilized, safeguarding any nonvolatile memory in the
system from inadvertent data changes.
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