Digital_power_monitor

Published:2009/7/24 12:03:00 Author:Jessie | From:SeekIC

This circuit shows a DS1231 power monitor chip that is used to control a digital-system power supply. The DS1231 uses a temperature-compensated reference circuit to provide both an orderly shutdown and automatic restart of processor-based systems. The DS1231 operates by monitoring the high-voltage inputs to the power-supply regulators (at a voltage sense point), and applying RST or RST and NMI (nonmaskable interrupt) control signals to the processor. 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 DS1231 unconditionally halts the processor (to prevent spurious cycles) by enabling reset when VCC falls below a selectable 5 or 10% threshold. Notice that the TOL pin is grounded for a 5% 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. Dallas Semiconductors, Product Data Book, 1992/1993, p. 10-40.



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