The MAX803/MAX809/MAX810 are microprocessor (μP) supervisory circuits used to monitor the power supplies in μP and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with +5V, +3.3V, +3.0V, or +2.5V powered circuits. These circuits perform a single function: they assert a reset signal whenever the VCC supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the reset threshold. Reset thresholds suitable for operation with a variety of supply voltages are available. The MAX803 has an open-drain output stage, while the MAX809/MAX810 have push-pull outputs. The MAX803’s open-drain RESET output requires a pullup resistor that can be connected to a voltage higher than VCC. The MAX803/MAX809 have an active-low RESET output, while the MAX810 has an active-high RESET output. The reset comparator is designed to ignore fast transients on VCC, and the outputs are guaranteed to be in the correct logic state for VCC down to 1V. Low supply current makes the MAX803/MAX809/MAX810 ideal for use in portable equipment. The MAX803 is available in a 3-pin SC70 package, and the MAX809/ MAX810 are available in 3-pin SC70 or SOT23 packages.