Jetson Nano and watchdog timer

i am using Jetson nano to make a board , i allready make the power supply of the board 5V as the Jetson nano need , my question is about the watchdog timer , is there a watchdog circuit built in Nano or should i make an external one? if yes what is the specifications of that circuits like ( threshold voltage ,…) ?
if not exisit is there any example how to connect this watchdog circiut to Nano and what components are needed ?

A watchdog timer normally checks for signs of life, and reboots if the signs of life fail for a given time. See:

If you are speaking of a hardware power monitoring tool, then you would need to add your own, but if you are speaking of the standard Linux watchdog timer, then this is already there (assuming you configure it). You might want to more closely describe what it is you expect for your use-case.