Integrated low voltage detect and watchdog circuit.

摘要

A low voltage monitor and microcontroller output monitoring circuit for insuring proper operation of a microcontroller in a furnace control system. A switch connected to a reset port of the microcontroller is capable of putting either a high or low voltage signal at the reset port. A high signal is required for normal operation of the microcontroller. The low voltage monitor connects to a power supply providing power to the microcontroller and causes the switch to provide a low signal to the reset port if the output voltage of the power supply drops below a predetermined level. The output monitoring circuit insures that the microcontroller is operating properly by insuring that the microcontroller is producing an output signal at a predetermined frequency and repetition rate. If the output signal is not at the predetermined frequency, the output monitoring circuit causes a low voltage to be present at the reset port.