I've designed a small AC-based watchdog circuit for my Raspberry Pi (schematic below). A buddy of mine looked at it and said that it was complicated, and there might be problems with asymmetric charge/discharge of the two capacitor's will be dependent on the rate & duty cycle of the watchdog tickle signal. I'm planning on tickling it with a software watchdog timer at around a 1Hz rate (the software watchdog will be running at sufficient priority to make that happen). VREF_MID is a resistor divider providing 2.5V.
Any problems with the circuit that jump out at anyone?
Thanks in advance!