The LM809 and LM810 microprocessors supervisory circuits can be used to monitor the power supplies in microprocessor and digital systems. They provide a reset to the microprocessor during power-up, power-down and brown-out conditions. The function of the LM809 and LM810 are to monitor the VCC supply voltage, and assert a reset signal whenever this voltage declines below the factory-programmed reset threshold. The reset signal remains asserted for 240 ms after VCC rises above the threshold. The LM809 has an active-low RESET output, while the LM810 has an active-high RESET output. Seven standard reset voltage options are available, suitable for monitoring 5-V, 3.3-V, and 3-V supply voltages. With a low supply current of only 15 µA, the LM809 and LM810 are ideal for use in portable equipment.