DS1231S

• Warns processor of an impending power failure
• Provides time for an orderly shutdown
• Prevents processor from destroying nonvolatile memory during power transients
• Automatically restarts processor after power is restored
• Suitable for linear or switching power supplies
• Adjusts to hold time of the power supply
• Supplies necessary signals for processor interface
• Accurate 5% or 10% V_CC monitoring
• Replaces power-up reset circuitry
• No external capacitors required
• Optional 16-pin SOIC surface mount package

The DS1231 Power Monitor Chip uses a precise temperature- compensated reference circuit which provides an orderly shutdown and an automatic restart of a processor- based system. A signal warning of an impending power failure is generated well before regulated DC voltages go out of specification by monitoring high voltage inputs to the power supply regulators. If line isolation is required a UL-approved opto-isolator can be directly 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 unconditionally halts the processor to prevent spurious cycles by enabling Reset as VCC falls below a selectable 5 or 10 percent threshold. When power returns, the processor is held inactive until well after power conditions have stabilized, safeguarding any nonvolatile memory in the system from inadvertent data changes.