General Description

The MAX792/MAX820 microprocessor (μP) supervisory circuits provide the most functions for power-supply and watchdog monitoring in systems without battery backup. Built-in features include the following:

? μP reset: Assertion of RESET and RESET outputs during

?? power-up, power-down, and brownout conditions.

?? RESET is guaranteed valid for VCC down to 1V.

? Manual-reset input.

? Two-stage power-fail warning: A separate low-line

?? comparator compares VCC to a preset threshold

?? 120mV above the reset threshold; the low-line and

?? reset thresholds can be programmed externally.

? Watchdog fault output: Assertion of WDO if the watchdog

?? input is not toggled within a preset timeout

?? period.

? Pulsed watchdog output: Advance warning of

?? impending WDO assertion from watchdog timeout that

?? causes hardware shutdown.

? Write protection of CMOS RAM, EEPROM, or other

?? memory devices.

??

The MAX792 and MAX820 are identical, except the MAX820 guarantees higher low-line and reset threshold accuracy (±2%).

特性 Features

? Manual-Reset Input

? 200ms Power-OK/Reset Time Delay

? Independent Watchdog Timer—Preset or Adjustable

? On-Board Gating of Chip-Enable Signals

? Memory Write-Cycle Completion

? 10ns (max) Chip-Enable Gate Propagation Delay

? Voltage Monitor for Overvoltage Warning

? ±2% Reset and Low-Line Threshold Accuracy

?? (MAX820, external programming mode)

Applications

?? Computers

?? Controllers

?? Intelligent Instruments

?? Critical μP Power Monitoring