The FM809/810 are supervisor circuits that monitor power supply or other system voltages and issue reset pulse whenever the voltage being monitored is out of tolerance. Once asserted, the reset pulse is guaranteed to be valid for a minimum of 140ms (256ms typical). FM809xx offers active low push-pull type of reset while FM810xx offers active high push-pull type. Several threshold voltages are offered to accommodate 5.0V, 3.3V, 3.0V and 2.7V system voltages.