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 active-low RESET outputs during power-up, power-down, and brownout
conditions. Active-low 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 active-low WDO if the watchdog input is not toggled within a preset timeout
period.
Pulsed watchdog output: Advance warning of impending active-low 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%).
Key Features
Applications/Uses
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)
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